Data binding in Vue Gantt component
11 Jun 202424 minutes to read
The Gantt uses DataManager, which supports both RESTful JSON data services binding and local JavaScript object array binding. The dataSource property can be assigned either with the instance of DataManager or JavaScript object array collection. Gantt provides support to bind two kinds of data,
- Local data
- Remote data
To learn about Gantt Chart data binding quickly, you can check on this video:
Local data
To bind local data to Gantt, you can assign a JavaScript object array to the dataSource property. The local data source can also be provided as an instance of the DataManager.
In local data binding, the data source for rendering the Gantt component is retrieved from the same application locally.
The following are the two types of data binding possible with the Gantt component:
- Hierarchical data binding.
- Self-referential data binding (Flat data).
Hierarchical data binding
The child property is used to map the child records in hierarchical data.
The following code example shows how to bind the hierarchical local data into the Gantt component.
<template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields="taskFields" :height="height"></ejs-gantt>
</div>
</template>
<script setup>
import { GanttComponent as EjsGantt } from "@syncfusion/ej2-vue-gantt";
const data = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
isParent: true,
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50, isParent: false },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50, resources: [2, 3, 5], isParent: false },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4, Predecessor: "2FS", Progress: 50, isParent: false },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
isParent: true,
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50, resources: [4], isParent: false },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50, resources: [4, 8], isParent: false },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 3, Predecessor: "6SS", Progress: 50, resources: [12, 5], isParent: false }
]
},
];
const height = '450px';
const taskFields = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
dependency: 'Predecessor',
child: 'subtasks'
};
</script><template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height"></ejs-gantt>
</div>
</template>
<script>
import { GanttComponent } from "@syncfusion/ej2-vue-gantt";
export default {
name: "App",
components: {
"ejs-gantt":GanttComponent
},
data: function() {
return{
data: [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
isParent:true,
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50,isParent:false },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50, resources: [2, 3, 5],isParent:false },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4,Predecessor:"2FS", Progress: 50,isParent:false },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
isParent:true,
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50, resources: [4],isParent:false },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50, resources: [4, 8],isParent:false },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 3,Predecessor:"6SS", Progress: 50, resources: [12, 5],isParent:false }
]
},
],
height: '450px',
taskFields: {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
dependency: 'Predecessor',
child: 'subtasks'
}
};
},
};
</script>Self-referential data binding (Flat data)
The Gantt component can be bound with self-referential data by mapping the data source field values to the id and parentID properties.
- ID field: This field contains unique values used to identify each individual task and it is mapped to the
idproperty. - Parent ID field: This field contains values that indicate parent tasks and it is mapped to the
parentIDproperty.
<template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height" :treeColumnIndex='1'></ejs-gantt>
</div>
</template>
<script setup>
import { GanttComponent as EjsGantt } from "@syncfusion/ej2-vue-gantt";
const data = [
{ TaskID: 1,TaskName: 'Project Initiation',StartDate: new Date('04/02/2019'),EndDate: new Date('04/21/2019')},
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50,ParentId:1 },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50, ParentId:1 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50,ParentId:1 },
{ TaskID: 5, TaskName: 'Project Estimation',StartDate: new Date('04/02/2019'),EndDate: new Date('04/21/2019')},
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50, ParentId:2 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50,ParentId:2 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50, ParentId:2 }
];
const height = '450px';
const taskFields = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
parentID:'ParentId'
};
</script><template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height" :treeColumnIndex='1'></ejs-gantt>
</div>
</template>
<script>
import { GanttComponent } from "@syncfusion/ej2-vue-gantt";
export default {
name: "App",
components: {
"ejs-gantt":GanttComponent
},
data: function() {
return{
data: [
{ TaskID: 1,TaskName: 'Project Initiation',StartDate: new Date('04/02/2019'),EndDate: new Date('04/21/2019')},
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50,ParentId:1 },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50, ParentId:1 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50,ParentId:1 },
{ TaskID: 5, TaskName: 'Project Estimation',StartDate: new Date('04/02/2019'),EndDate: new Date('04/21/2019')},
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50, ParentId:2 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50,ParentId:2 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50, ParentId:2 }
],
height: '450px',
taskFields: {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
parentID:'ParentId'
}
};
},
};
</script>Remote data
To bind remote data to the Gantt component, assign service data as an instance of DataManager to the dataSource property.
<template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height"></ejs-gantt>
</div>
</template>
<script setup>
import { GanttComponent as EjsGantt } from "@syncfusion/ej2-vue-gantt";
import { DataManager, WebApiAdaptor } from '@syncfusion/ej2-data';
const data = new DataManager({
url: 'https://ej2services.syncfusion.com/production/web-services/api/GanttData',
adaptor: new WebApiAdaptor,
crossDomain: true
});
const height = '450px';
const taskFields = {
id: 'TaskId',
name: 'TaskName',
startDate: 'StartDate',
progress: 'Progress',
duration: 'Duration',
dependency: 'Predecessor',
child: 'SubTasks'
};
</script><template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height"></ejs-gantt>
</div>
</template>
<script>
import { GanttComponent } from "@syncfusion/ej2-vue-gantt";
import { DataManager, WebApiAdaptor } from '@syncfusion/ej2-data';
export default {
name: "App",
components: {
"ejs-gantt":GanttComponent
},
data: function() {
return{
data: new DataManager({
url: 'https://ej2services.syncfusion.com/production/web-services/api/GanttData',
adaptor: new WebApiAdaptor,
crossDomain: true
}),
height: '450px',
taskFields: {
id: 'TaskId',
name: 'TaskName',
startDate: 'StartDate',
progress: 'Progress',
duration: 'Duration',
dependency: 'Predecessor',
child: 'SubTasks'
}
};
},
};
</script>URL Adaptor
In Gantt, we can fetch data from SQL database using ADO.NET Entity Data Model and update the changes on CRUD action to the server by using DataManager support. To communicate with the remote data we are using UrlAdaptor of DataManager property to call the server method and get back resultant data in JSON format. We can know more about UrlAdaptor from here.
Please refer the link to create the
ADO.NETEntity Data Model in Visual studio,
We can define data source for Gantt as instance of DataManager using url property of DataManager. Please Check the below code snippet to assign data source to Gantt.
<template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields="taskFields" :height="height"></ejs-gantt>
</div>
</template>
<script setup>
import { GanttComponent as EjsGantt } from "@syncfusion/ej2-vue-gantt";
import { DataManager, UrlAdaptor } from '@syncfusion/ej2-data';
const data = new DataManager({
url: '/Home/UrlDatasource',
adaptor: new UrlAdaptor
});
const height = '450px';
const taskFields = {
id: 'TaskId',
name: 'TaskName',
startDate: 'StartDate',
progress: 'Progress',
duration: 'Duration',
dependency: 'Predecessor',
child: 'SubTasks'
}
</script>
GanttDataSourceEntities db = new GanttDataSourceEntities();
public ActionResult UrlDatasource(DataManagerRequest dm)
{
List<GanttData>DataList = db.GanttDatas.ToList();
var count = DataList.Count();
return Json(new { result = DataList, count = count });
}Remote Save Adaptor
You may need to perform all Gantt Actions on the client-side except the CRUD operations, which should be interacted with the server-side to persist data. It can be achieved in Gantt by using RemoteSaveAdaptor.
Datasource must be set to the json property and set RemoteSaveAdaptor to the adaptor property. CRUD operations can be mapped to the server-side using the batchUrl properties.
You can use the following code example to use RemoteSaveAdaptor in Gantt.
<template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height"></ejs-gantt>
</div>
</template>
<script setup>
import { GanttComponent as EjsGantt, Edit } from "@syncfusion/ej2-vue-gantt";
import { DataManager, RemoteSaveAdaptor } from '@syncfusion/ej2-data';
const data = new DataManager({
url: 'https://js.syncfusion.com/demos/ejServices/Wcf/Northwind.svc/Tasks/'
});
const height = '450px';
const taskFields = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
duration: 'Duration',
progress: 'Progress',
child: 'subtasks'
};
const editSettings = {
allowAdding: true,
allowEditing: true,
allowDeleting: true,
allowTaskbarEditing: true,
showDeleteConfirmDialog: true
};
</script>
The following code example describes the CRUD operations handled at server-side.
public IActionResult BatchUpdate([FromBody] CRUDModel batchmodel)
{
public class CRUDModel
{
public List<GanttDataSource> added { get; set; }
public List<GanttDataSource> changed { get; set; }
public List<GanttDataSource> deleted { get; set; }
public object key { get; set; }
public string action { get; set; }
public string table { get; set; }
}
public IActionResult BatchUpdate([FromBody] CRUDModel batchmodel)
{
if (batchmodel.changed != null)
{
for (var i = 0; i < batchmodel.changed.Count(); i++)
{
var value = batchmodel.changed[i];
GanttDataSource result = DataList.Where(or => or.taskId == value.taskId).FirstOrDefault();
result.taskId = value.taskId;
result.taskName = value.taskName;
result.startDate = value.startDate;
result.endDate = value.endDate;
result.duration = value.duration;
result.progress = value.progress;
result.parentID = value.parentID;
}
}
if (batchmodel.deleted != null)
{
for (var i = 0; i < batchmodel.deleted.Count(); i++)
{
DataList.Remove(DataList.Where(or => or.taskId.Equals(batchmodel.deleted[i].taskId)).FirstOrDefault());
RemoveChildRecords(batchmodel.deleted[i].taskId);
}
}
if (batchmodel.added != null)
{
for (var i = 0; i < batchmodel.added.Count(); i++)
{
DataList.Add(batchmodel.added[i]);
}
}
return Json(new { addedRecords = batchmodel.added, changedRecords = batchmodel.changed, deletedRecords = batchmodel.deleted });
}
public void RemoveChildRecords(int key)
{
var childList = DataList.Where(x => x.parentID == key).ToList();
foreach (var item in childList)
{
DataList.Remove(item);
RemoveChildRecords(item.taskId);
}
}
return Json(new { addedRecords = batchmodel.added, changedRecords = batchmodel.changed, deletedRecords = batchmodel.deleted });
}
Load child on demand
To render child records on demand, assign a remote service URL in the instance of DataManager to the Url property. To interact with the remote data source, provide the endpoint URL and also define the hasChildMapping property in taskFields of Gantt Chart.
The hasChildMapping property maps the field name in the data source, which denotes whether the current record holds any child records. This is useful internally to show expand icon while binding child data on demand.
When loadChildOnDemand is disabled, all the root nodes are rendered in a collapsed state at initial load. On expanding the root node, the child nodes will be loaded from the remote server.
When enableVirtualization is enabled and loadChildOnDemand is disabled, only the current viewport root nodes are rendered in a collapsed state.
When a root node is expanded, its child nodes are rendered and maintained in a collection locally, such that on consecutive expand/collapse actions on the root node, the child nodes are loaded locally instead of from the remote server.
When the loadChildOnDemand is enabled, parent records are rendered in an expanded state.
<template>
<div id="app">
<ejs-gantt ref='gantt' id="GanttContainer"
:dataSource= "dataSource"
:taskFields= "taskFields"
:allowSelection= "true"
:allowResizing= "true"
:height= "height"
:treeColumnIndex= "1"
:highlightWeekends= "true"
:columns= "columns"
:enableVirtualization="true"
:loadChildOnDemand = "false"
:projectStartDate= "projectStartDate"
:projectEndDate= "projectEndDate"
:splitterSettings= "splitterSettings"
>
</ejs-gantt>
</div>
</template>
<script setup>
import { provide } from "vue";
import { GanttComponent as EjsGantt, GanttComponent as EjsGantt, Selection, VirtualScroll } from "@syncfusion/ej2-vue-gantt";
import { DataManager, WebApiAdaptor } from '@syncfusion/ej2-data';
const data = new DataManager({
url: 'https://services.syncfusion.com/vue/production/api/GanttLoadOnDemand',
adaptor: new WebApiAdaptor,
crossDomain: true
});
const projectStartDate = new Date('01/02/2000');
const projectEndDate = new Date('12/01/2002');
const splitterSettings = {
columnIndex: 3
};
const taskFields = {
id: 'taskId',
name: 'taskName',
startDate: 'startDate',
endDate: 'endDate',
duration: 'duration',
progress: 'progress',
hasChildMapping: 'isParent',
parentID: 'parentID'
};
const height = '460px';
const columns = [
{ field: 'taskId' },
{ field: 'taskName', headerText: 'Task Name', width: '250', clipMode: 'EllipsisWithTooltip' },
{ field: 'startDate' },
{ field: 'duration' },
{ field: 'progress' }
];
provide('gantt', [ Selection, VirtualScroll]);
</script>
The following code example describes handling of Load on demand at server end.
public object Get()
{
DataOperations operation = new DataOperations();
var queryString = Request.Query;
if (tree.Count == 0)
tree = TreeData.GetTree();
if (queryString.Keys.Contains("$filter") && !queryString.Keys.Contains("$top"))
{
StringValues filter;
queryString.TryGetValue("$filter", out filter);
int? fltr;
if (filter[0].ToString().Split("eq")[1] == " null")
{
fltr = null;
}
else
{
fltr = Int32.Parse(filter[0].ToString().Split("eq")[1]);
}
IQueryable<TreeData> data1 = tree.Where(f => f.parentID == fltr).AsQueryable();
return new { result = data1.ToList(), count = data1.Count() };
}
StringValues expand;
queryString.TryGetValue("$expand", out expand);
if (queryString.Keys.Contains("$expand")) // setting the ExpandStateMapping property whether is true or false
{
if (expand[0].ToString().Split(",")[0] == "ExpandingAction")
{
var val = TreeData.GetTree().Where(ds => ds.taskId == int.Parse(expand[0].ToString().Split(",")[1])).FirstOrDefault();
val.IsExpanded = true;
}
else if (expand[0].ToString().Split(",")[0] == "CollapsingAction")
{
var val = TreeData.GetTree().Where(ds => ds.taskId == int.Parse(expand[0].ToString().Split(",")[1])).FirstOrDefault();
val.IsExpanded = false;
}
}
List<TreeData> data = tree.ToList();
if (queryString.Keys.Contains("$select"))
{
data = (from ord in tree
select new TreeData
{
parentID = ord.parentID
}
).ToList();
return data;
}
data = data.Where(p => p.parentID == null).ToList();
int count = data.Count;
if (queryString.Keys.Contains("$inlinecount"))
{
StringValues Skip;
StringValues Take;
StringValues loadchild;
int skip = (queryString.TryGetValue("$skip", out Skip)) ? Convert.ToInt32(Skip[0]) : 0;
int top = (queryString.TryGetValue("$top", out Take)) ? Convert.ToInt32(Take[0]) : data.Count();
var GroupData = TreeData.GetTree().ToList().GroupBy(rec => rec.parentID)
.Where(g => g.Key != null).ToDictionary(g => g.Key?.ToString(), g => g.ToList());
foreach (var Record in data.ToList())
{
if (GroupData.ContainsKey(Record.taskId.ToString()))
{
var ChildGroup = GroupData[Record.taskId.ToString()];
if (ChildGroup?.Count > 0)
AppendChildren(ChildGroup, Record, GroupData, data);
}
}
if (expand.Count > 0 && expand[0].ToString().Split(",")[0] == "CollapsingAction")
{
string IdMapping = "taskId";
List<WhereFilter> CollapseFilter = new List<WhereFilter>();
CollapseFilter.Add(new WhereFilter() { Field = IdMapping, value = expand[0].ToString().Split(",")[1], Operator = "equal" });
var CollapsedParentRecord = operation.PerformFiltering(data, CollapseFilter, "and");
var index = data.Cast<object>().ToList().IndexOf(CollapsedParentRecord.Cast<object>().ToList()[0]);
skip = index;
}
else if (expand.Count > 0 && expand[0].ToString().Split(",")[0] == "ExpandingAction")
{
string IdMapping = "taskId";
List<WhereFilter> ExpandFilter = new List<WhereFilter>();
ExpandFilter.Add(new WhereFilter() { Field = IdMapping, value = expand[0].ToString().Split(",")[1], Operator = "equal" });
var ExpandedParentRecord = operation.PerformFiltering(data, ExpandFilter, "and");
var index = data.Cast<object>().ToList().IndexOf(ExpandedParentRecord.Cast<object>().ToList()[0]);
skip = index;
}
return new { result = data.Skip(skip).Take(top), count = data.Count };
}
else
{
return TreeData.GetTree();
}
}
private void AppendChildren(List<TreeData> ChildRecords, TreeData ParentItem, Dictionary<string, List<TreeData>> GroupData, List<TreeData> data)
{
var queryString = Request.Query;
string TaskId = ParentItem.taskId.ToString();
var index = data.IndexOf(ParentItem);
foreach (var Child in ChildRecords)
{
string ParentId = Child.parentID.ToString();
if (TaskId == ParentId && (bool)ParentItem.IsExpanded)
{
if (data.IndexOf(Child) == -1)
((IList)data).Insert(++index, Child);
if (GroupData.ContainsKey(Child.taskId.ToString()))
{
var DeepChildRecords = GroupData[Child.taskId.ToString()];
if (DeepChildRecords?.Count > 0)
AppendChildren(DeepChildRecords, Child, GroupData, data);
}
}
}
}
// GET: api/Orders/
[HttpGet("{id}", Name = "Get")]
public string Get(int id)
{
return "value";
}
[HttpPost]
public object Post([FromBody] TreeData[] value)
{
//handle insert action
for (var i = 0; i < value.Length; i++)
{
tree.Insert(0, value[i]);
}
return value;
}
//// PUT: api/Orders
[HttpPut]
public object Put([FromBody] TreeData[] value)
{
//handle edit action
if (value.Length == 1 && value[0].isParent == true)
{
UpdateDependentRecords(value[0]);
}
for (var i = 0; i < value.Length; i++) {
var ord = value[i];
TreeData val = tree.Where(or => or.taskId == ord.taskId).FirstOrDefault();
val.taskId = ord.taskId;
val.taskName = ord.taskName;
val.endDate = ord.endDate;
val.startDate = ord.startDate;
val.duration = ord.duration;
val.predecessor = ord.predecessor;
}
return value;
}
private void UpdateDependentRecords(TreeData ParentItem)
{
var data = tree.Where(p => p.parentID == ParentItem.taskId).ToList();
var previousData = tree.Where(p => p.taskId == ParentItem.taskId).ToList();
var previousStartDate = previousData[0].startDate;
var previousEndDate = previousData[0].endDate;
double sdiff = (double)GetTimeDifference((DateTime)previousStartDate, (DateTime)ParentItem.startDate);
double ediff = (double)GetTimeDifference((DateTime)previousEndDate, (DateTime)ParentItem.endDate);
GetRootChildRecords(ParentItem);
for(var i=0; i<ChildRecords.Count;i++)
{
ChildRecords[i].startDate = ((DateTime)ChildRecords[i].startDate).AddSeconds(sdiff);
ChildRecords[i].endDate = ((DateTime)ChildRecords[i].endDate).AddSeconds(ediff);
}
}
private void GetRootChildRecords(TreeData ParentItem)
{
var currentchildRecords = tree.Where(p => p.parentID == ParentItem.taskId).ToList();
for (var i = 0; i < currentchildRecords.Count; i++) {
var currentRecord = currentchildRecords[i];
ChildRecords.Add(currentRecord);
if (currentRecord.isParent == true)
{
GetRootChildRecords(currentRecord);
}
}
}
public object GetTimeDifference(DateTime sdate, DateTime edate)
{
return new DateTime(edate.Year, edate.Month, edate.Day, edate.Hour, edate.Minute, edate.Second, DateTimeKind.Utc).Subtract(new DateTime(sdate.Year, sdate.Month, sdate.Day, sdate.Hour, sdate.Minute, sdate.Second, DateTimeKind.Utc)).TotalSeconds;
}
// DELETE: api/ApiWithActions
[HttpDelete("{id:int}")]
[Route("Orders/{id:int}")]
public object Delete(int id)
{
//handle delete action
tree.Remove(tree.Where(or => or.taskId == id).FirstOrDefault());
return Json(id);
}
public class CRUDModel<T> where T : class
{
public TreeData Value;
public int Key { get; set; }
public int RelationalKey { get; set; }
public List<TreeData> added { get; set; }
public List<TreeData> changed { get; set; }
public List<TreeData> deleted { get; set; }
}
public class TreeData
{
public static List<TreeData> tree = new List<TreeData>();
[System.ComponentModel.DataAnnotations.Key]
public int taskId { get; set; }
public string taskName { get; set; }
public DateTime startDate { get; set; }
public DateTime endDate { get; set; }
public string duration { get; set; }
public int progress { get; set; }
public int? parentID { get; set; }
public string predecessor { get; set; }
public bool? isParent { get; set; }
public bool? IsExpanded { get; set; }
public static List<TreeData> GetTree()
{
if (tree.Count == 0)
{
Random rand = new Random();
var x = 0;
int duration = 0;
DateTime startDate = new DateTime(2000, 1, 3, 08, 00, 00);
for (var i = 1; i <= 50; i++)
{
startDate = startDate.AddDays(i == 1 ? 0 : 7);
DateTime childStartDate = startDate;
TreeData Parent = new TreeData()
{
taskId = ++x,
taskName = "Task " + x,
startDate = startDate,
endDate = childStartDate.AddDays(26),
duration = "20",
progress = rand.Next(100),
predecessor = null,
isParent = true,
parentID = null,
IsExpanded = false
};
tree.Add(Parent);
for (var j = 1; j <= 4; j++)
{
childStartDate = childStartDate.AddDays(j == 1 ? 0 : duration + 2);
duration = 5;
tree.Add(new TreeData()
{
taskId = ++x,
taskName = "Task " + x,
startDate = childStartDate,
endDate = childStartDate.AddDays(5),
duration = duration.ToString(),
progress = rand.Next(100),
parentID = Parent.taskId,
predecessor = (j > 1 ? (x - 1) + "FS" : ""),
isParent = false,
IsExpanded = false
});
}
}
}
return tree;
}
}Limitations
- Filtering, sorting and searching are not supported in load on demand.
- Only Self-Referential type data is supported with remote data binding in Gantt Chart.
- Load-on-demand supports only the validated data source
Sending additional parameters to the server
We can pass additional parameters using addParams method of Query class. In server side we have inherited and shown the additional parameter value in Syncfusion DataManager class itself. We pass an additional parameter in load time using load event. We can also pass additional parameter to the CRUD model. Please Check the below code snippet to send additional parameter to Gantt.
<template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height" :toolbar="toolbar" :editSettings= "editSettings" :load= "load"></ejs-gantt>
</div>
</template>
<script setup>
import { provide } from "vue";
import { GanttComponent as EjsGantt, Edit, Toolbar } from "@syncfusion/ej2-vue-gantt";
import { DataManager, UrlAdaptor, Query } from '@syncfusion/ej2-data';
const data = new DataManager({
url: 'http://localhost:50039/Home/UrlDatasource',
adaptor: new UrlAdaptor,
batchUrl: 'http://localhost:50039/Home/BatchSave'
});
const height = '450px';
const taskFields = {
id: 'TaskId',
name: 'TaskName',
startDate: 'StartDate',
progress: 'Progress',
duration: 'Duration',
dependency: 'Predecessor',
parentID: 'parentID'
};
const toolbar = ['Add', 'Edit', 'Delete', 'Cancel', 'ExpandAll', 'CollapseAll', 'Update'];
const editSettings = {
allowAdding: true,
allowEditing: true,
allowDeleting: true
};
const load = (args) => {
this.query = new Query().addParams('ej2Gantt', "test");
};
provide('gantt', [Edit, Toolbar]);
</script>
namespace URLAdaptor.Controllers
{
public class HomeController : Controller
{
...///
//inherit the class to show age as property of DataManager
public class Test : DataManagerRequest
{
public string ej2Gantt { get; set; }
}
public ActionResult UrlDatasource([FromBody]Test dm)
{
if (DataList == null)
{
ProjectData datasource = new ProjectData();
DataList = datasource.GetUrlDataSource();
}
var count = DataList.Count();
return Json(new { result = DataList, count = count }, JsonRequestBehavior.AllowGet);
}
...///
public class ICRUDModel<T> where T : class
{
public object key { get; set; }
public T value { get; set; }
public List<T> added { get; set; }
public List<T> changed { get; set; }
public List<T> deleted { get; set; }
public IDictionary<string, object> @params { get; set; }
}
...///
}
}You can find the full sample from here.
Handling HTTP error
During server interaction from the Gantt, some server-side exceptions may occur, and you can acquire those error messages or exception details in client-side using the actionFailure event.
The argument passed to the actionFailure event contains the error details returned from the server.
<template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height" :actionFailure= "actionFailure"></ejs-gantt>
</div>
</template>
<script setup>
import { GanttComponent as EjsGantt } from "@syncfusion/ej2-vue-gantt";
import { DataManager } from '@syncfusion/ej2-data';
import { ref } from 'vue';
const gantt = ref(null);
const data = new DataManager({
url: 'http://some.com/invalidUrl',
});
const height = '450px';
const taskFields = {
id: 'TaskId',
name: 'TaskName',
startDate: 'StartDate',
progress: 'Progress',
duration: 'Duration',
dependency: 'Predecessor',
parentID: 'parentID'
};
const actionFailure = function(args){
let gantt = gantt.value.ej2Instances; // Gantt instance
let span = document.createElement('span');
this.element.parentNode.insertBefore(span, gantt.element);
span.style.color = '#FF0000'
span.innerHTML = 'Server exception: 404 Not found';
};
</script><template>
<div>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height" :actionFailure= "actionFailure"></ejs-gantt>
</div>
</template>
<script>
import { GanttComponent } from "@syncfusion/ej2-vue-gantt";
import { DataManager } from '@syncfusion/ej2-data';
export default {
name: "App",
components: {
"ejs-gantt":GanttComponent
},
data: function() {
return{
data: new DataManager({
url: 'http://some.com/invalidUrl',
}),
height: '450px',
taskFields: {
id: 'TaskId',
name: 'TaskName',
startDate: 'StartDate',
progress: 'Progress',
duration: 'Duration',
dependency: 'Predecessor',
parentID: 'parentID'
},
actionFailure: function(args){
let gantt = document.getElementsByClassName("e-gantt")[0].ej2_instances[0]; // Gantt instance
let span = document.createElement('span');
this.element.parentNode.insertBefore(span, gantt.element);
span.style.color = '#FF0000'
span.innerHTML = 'Server exception: 404 Not found';
}, };
}
};
</script>Binding with Ajax
You can use Gantt dataSource property to bind the data source to Gantt from external Ajax request. In the below code we have fetched the data source from the server with the help of Ajax request and provided that to dataSource property by using onSuccess event of the Ajax.
<template>
<div>
<ejs-button id="databind" cssClass="e-info" v-on:click.native="databind">Bind Data</ejs-button>
<br>
<br>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height" :projectStartDate="projectStartDate" :projectEndDate= "projectEndDate"></ejs-gantt>
</div>
</template>
<script setup>
import { GanttComponent as EjsGantt } from "@syncfusion/ej2-vue-gantt";
import { Ajax } from '@syncfusion/ej2-base';
const height = '450px';
const taskFields = {
id: 'TaskId',
name: 'TaskName',
startDate: 'StartDate',
progress: 'Progress',
duration: 'Duration',
dependency: 'Predecessor',
child: 'SubTasks'
};
const projectStartDate = new Date('02/24/2019');
const projectEndDate = new Date('07/20/2019');
const databind = function(e){
let ajax = new Ajax("https://ej2services.syncfusion.com/production/web-services/api/GanttData","GET");
this.showSpinner();
ajax.send();
ajax.onSuccess = function (data) {
this.hideSpinner();
this.dataSource = (JSON.parse(data)).Items;
this.refresh();
};
};
</script><template>
<div>
<ejs-button id="databind" cssClass="e-info" v-on:click.native="databind">Bind Data</ejs-button>
<br>
<br>
<ejs-gantt ref='gantt' :dataSource="data" id="GanttContainer" :taskFields = "taskFields" :height = "height" :projectStartDate="projectStartDate" :projectEndDate= "projectEndDate"></ejs-gantt>
</div>
</template>
<script>
import { GanttComponent } from "@syncfusion/ej2-vue-gantt";
import { Ajax } from '@syncfusion/ej2-base';
export default {
name: "App",
components: {
"ejs-button":ButtonComponent,
"ejs-gantt":GanttComponent
},
data: function() {
return{
height: '450px',
taskFields: {
id: 'TaskId',
name: 'TaskName',
startDate: 'StartDate',
progress: 'Progress',
duration: 'Duration',
dependency: 'Predecessor',
child: 'SubTasks'
},
projectStartDate: new Date('02/24/2019'),
projectEndDate: new Date('07/20/2019')
};
},
methods: {
databind: function(e){
let ajax = new Ajax("https://ej2services.syncfusion.com/production/web-services/api/GanttData","GET");
this.showSpinner();
ajax.send();
ajax.onSuccess = function (data) {
this.hideSpinner();
this.dataSource = (JSON.parse(data)).Items;
this.refresh();
};
},
}
};
</script>Note: If you bind the dataSource from this way, then it acts like a local dataSource. So you cannot perform any server side crud actions.
Split task
The Split-task feature allows you to split a task or interrupt the work during planned or unforeseen circumstances. We can split the task either in load time or dynamically, by defining the segments either in hierarchical or self-referential way.
Hierarchical
To split a task at load time in hierarchical way, we need to define the segment details in datasource and this field should be mapped by using the taskFields.segments property.
[
{
TaskID: 1, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50,
Segments: [
{ StartDate: new Date("04/02/2019"), Duration: 2 },
{ StartDate: new Date("04/04/2019"), Duration: 2 }
]
}
]<template>
<div>
<ejs-gantt ref='gantt' id="GanttContainer" :dataSource="data" :taskFields="taskFields" :height="height"></ejs-gantt>
</div>
</template>
<script setup>
import { GanttComponent as EjsGantt } from "@syncfusion/ej2-vue-gantt";
const data = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{
TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50,
Segments: [
{ StartDate: new Date("04/02/2019"), Duration: 2 },
{ StartDate: new Date("04/04/2019"), Duration: 2 }
]
},
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 }
]
}
];
const height = '450px';
const taskFields = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
endDate: 'EndDate',
duration: 'Duration',
progress: 'Progress',
child: 'subtasks',
segments: 'Segments'
};
</script><template>
<div>
<ejs-gantt ref='gantt' id="GanttContainer" :dataSource="data" :taskFields = "taskFields" :height = "height"></ejs-gantt>
</div>
</template>
<script>
import { GanttComponent } from "@syncfusion/ej2-vue-gantt";
export default {
name: "App",
components: {
"ejs-gantt":GanttComponent
},
data: function() {
return{
data: [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50,
Segments: [
{ StartDate: new Date("04/02/2019"), Duration: 2 },
{ StartDate: new Date("04/04/2019"), Duration: 2 }
] },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4 , Progress: 50 },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 }
]
}
],
height: '450px',
taskFields: {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
endDate: 'EndDate',
duration: 'Duration',
progress: 'Progress',
child: 'subtasks',
segments: 'Segments'
}
};
}
};
</script>Self-referential
We can also define segment details as a flat data and this collection can be mapped by using segmentData property. The segment id field of this collection is mapped by using the taskFields.segmentId property.
taskFields: {
segmentId: "segmentId"
},
segmentData: [
{ segmentId: 1, StartDate: new Date("02/04/2019"), Duration: 2 },
{ segmentId: 1, StartDate: new Date("02/05/2019"), Duration: 5 },
{ segmentId: 4, StartDate: new Date("04/02/2019"), Duration: 2 },
{ segmentId: 4, StartDate: new Date("04/04/2019"), Duration: 2 }
],<template>
<div>
<ejs-gantt ref='gantt' id="GanttContainer" :dataSource="data" :taskFields = "taskFields" :height = "height" :segmentData = "segmentData"></ejs-gantt>
</div>
</template>
<script setup>
import { GanttComponent as EjsGantt } from "@syncfusion/ej2-vue-gantt";
const data = [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50,
Segments: [
{ StartDate: new Date("04/02/2019"), Duration: 2 },
{ StartDate: new Date("04/04/2019"), Duration: 2 }
] },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4 , Progress: 50 },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 }
]
}
];
const height = '450px';
const taskFields = {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
endDate: 'EndDate',
duration: 'Duration',
progress: 'Progress',
child: 'subtasks',
segments: 'Segments'
};
const segmentData = [
{ segmentId: 2, StartDate: new Date("04/02/2019"), Duration: 2 },
{ segmentId: 2, StartDate: new Date("04/04/2019"), Duration: 2 },
{ segmentId: 4, StartDate: new Date("04/02/2019"), Duration: 2 },
{ segmentId: 4, StartDate: new Date("04/04/2019"), Duration: 2 }
];
</script><template>
<div>
<ejs-gantt ref='gantt' id="GanttContainer" :dataSource="data" :taskFields = "taskFields" :height = "height" :segmentData = "segmentData"></ejs-gantt>
</div>
</template>
<script>
import { GanttComponent } from "@syncfusion/ej2-vue-gantt";
export default {
name: "App",
components: {
"ejs-gantt":GanttComponent
},
data: function() {
return{
data: [
{
TaskID: 1,
TaskName: 'Project Initiation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 2, TaskName: 'Identify Site location', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50,
Segments: [
{ StartDate: new Date("04/02/2019"), Duration: 2 },
{ StartDate: new Date("04/04/2019"), Duration: 2 }
] },
{ TaskID: 3, TaskName: 'Perform Soil test', StartDate: new Date('04/02/2019'), Duration: 4, Progress: 50 },
{ TaskID: 4, TaskName: 'Soil test approval', StartDate: new Date('04/02/2019'), Duration: 4 , Progress: 50 },
]
},
{
TaskID: 5,
TaskName: 'Project Estimation',
StartDate: new Date('04/02/2019'),
EndDate: new Date('04/21/2019'),
subtasks: [
{ TaskID: 6, TaskName: 'Develop floor plan for estimation', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 7, TaskName: 'List materials', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 },
{ TaskID: 8, TaskName: 'Estimation approval', StartDate: new Date('04/04/2019'), Duration: 3, Progress: 50 }
]
}
],
height: '450px',
taskFields: {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
endDate: 'EndDate',
duration: 'Duration',
progress: 'Progress',
child: 'subtasks',
segments: 'Segments'
},
segmentData: [
{ segmentId: 2, StartDate: new Date("04/02/2019"), Duration: 2 },
{ segmentId: 2, StartDate: new Date("04/04/2019"), Duration: 2 },
{ segmentId: 4, StartDate: new Date("04/02/2019"), Duration: 2 },
{ segmentId: 4, StartDate: new Date("04/04/2019"), Duration: 2 }
]
};
}
};
</script>Note: Segment id field contains id of a task which should be split at load time.
Improve performance by disabling validations
The autoCalculateDateScheduling property can help you reduce the time taken for the Gantt chart to render on the initial load. When this API is enabled, parent-child validation, data validation, and predecessor validation are restricted, allowing the Gantt chart to load more quickly. Since we are disabling the validations, data source provided to gantt should have all data such as start date, end date, duration, as proper data.
<template>
</template>
<script setup>
import { provide } from "vue";
import { GanttComponent as EjsGantt, Selection, VirtualScroll,Edit } from "@syncfusion/ej2-vue-gantt";
import{tempData} from "./datasource.js";
var virtualData = [];
var projId = 1;
for (var i = 0; i < 50; i++) {
var x = virtualData.length + 1;
var parent_1 = {};
parent_1['TaskID'] = x;
parent_1['TaskName'] = 'Project' + (projId++);
virtualData.push(parent_1);
for (var j = 0; j < tempData.length; j++) {
var subtasks = {};
subtasks['TaskID'] = tempData[j].TaskID + x;
subtasks['TaskName'] = tempData[j].TaskName;
subtasks['StartDate'] = tempData[j].StartDate;
subtasks['Duration'] = tempData[j].Duration;
subtasks['Progress'] = tempData[j].Progress;
subtasks['parentID'] = tempData[j].parentID + x;
virtualData.push(subtasks);
}
}
new Vue({
el: '#app',
template: `
<div>
<ejs-gantt ref='gantt'
:dataSource= "data"
:taskFields= "taskFields"
:allowSelection= "true"
:enableVirtualization= "true"
:labelSettings= "labelSettings"
:height= "height"
:treeColumnIndex= "1"
:highlightWeekends= "true"
:columns= "columns"
:autoCalculateDateScheduling='false',
:editSettings= "editSettings"
:splitterSettings= "splitterSettings">
</ejs-gantt>
</div>
`,
data: function() {
return{
data : virtualData,
taskFields: {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
endDate: 'EndDate',
duration: 'Duration',
progress: 'Progress',
parentID: 'parentID'
},
columns: [
{ field: 'TaskID' },
{ field: 'TaskName' },
{ field: 'StartDate' },
{ field: 'Duration' },
{ field: 'Progress' }
],
height: '450px',
labelSettings: {
taskLabel: 'Progress'
},
splitterSettings: {
columnIndex: 2
},
editSettings:{
allowAdding:true
},
}
}
,
provide('gantt', [ Selection, VirtualScroll,Edit]);
});
</script><template>
</template>
<script>
import { GanttComponent, Selection, VirtualScroll,Edit } from "@syncfusion/ej2-vue-gantt";
import{tempData} from "./datasource.js";
var virtualData = [];
var projId = 1;
for (var i = 0; i < 50; i++) {
var x = virtualData.length + 1;
var parent_1 = {};
parent_1['TaskID'] = x;
parent_1['TaskName'] = 'Project' + (projId++);
virtualData.push(parent_1);
for (var j = 0; j < tempData.length; j++) {
var subtasks = {};
subtasks['TaskID'] = tempData[j].TaskID + x;
subtasks['TaskName'] = tempData[j].TaskName;
subtasks['StartDate'] = tempData[j].StartDate;
subtasks['Duration'] = tempData[j].Duration;
subtasks['Progress'] = tempData[j].Progress;
subtasks['parentID'] = tempData[j].parentID + x;
virtualData.push(subtasks);
}
}
new Vue({
el: '#app',
template: `
<div>
<ejs-gantt ref='gantt'
:dataSource= "data"
:taskFields= "taskFields"
:allowSelection= "true"
:enableVirtualization= "true"
:labelSettings= "labelSettings"
:height= "height"
:treeColumnIndex= "1"
:highlightWeekends= "true"
:columns= "columns"
:autoCalculateDateScheduling='false',
:editSettings= "editSettings"
:splitterSettings= "splitterSettings">
</ejs-gantt>
</div>
`,
data: function() {
return{
data : virtualData,
taskFields: {
id: 'TaskID',
name: 'TaskName',
startDate: 'StartDate',
endDate: 'EndDate',
duration: 'Duration',
progress: 'Progress',
parentID: 'parentID'
},
columns: [
{ field: 'TaskID' },
{ field: 'TaskName' },
{ field: 'StartDate' },
{ field: 'Duration' },
{ field: 'Progress' }
],
height: '450px',
labelSettings: {
taskLabel: 'Progress'
},
splitterSettings: {
columnIndex: 2
},
editSettings:{
allowAdding:true
},
}
}
,
provide: {
gantt: [ Selection, VirtualScroll,Edit]
}
});
</script>Limitations
Gantt has the support for both Hierarchical and Self-Referential data binding. When rendering the Gantt control with SQL database, we suggest you to use the Self-Referential data binding to maintain the parent-child relation. Because the complex json structure is very difficult to manage it in SQL tables, we need to write a complex queries and we have to write a complex algorithm to find out the proper record details while updating/deleting the inner level task in Gantt data source. We cannot implement both data binding for Gantt control and this is not a recommended way. If both child and parentID are mapped, the records will not render properly because, when task id of a record defined in the hierarchy structure is assigned to parent id of another record, in such case the records will not properly render. As the self-referential will search the record with particular id in flat data only, not in the inner level of records. If we map the parentID field, it will be prioritized and Gantt will be rendered based on the parentID values.