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Task Dependencies

Task dependency or task relationship can be established between two tasks in Gantt. This dependency affects the project schedule. If you change the predecessor of a task, it will affect the successor task, which will affect the next task, and so on.

Task relationship types

Task relationships are categorized into four types based on the start and finish dates of the task.

Start to Start (SS)

You cannot start a task until the dependent task also starts.

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Start to Finish (SF)

You cannot finish a task until the dependent task is started.

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Finish to Start (FS)

You cannot start a task until the dependent task is completed.

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Finish to Finish (FF)

You cannot finish a task until the dependent task is completed.

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Define task relationship

Task relationship is defined in the data source as a string value, and this value is mapped to the Gantt component by using the TaskFields.Dependency property. The following code example demonstrates how to enable the predecessor in the Gantt component.

@using Syncfusion.EJ2.Blazor.Gantt
<EjsGantt DataSource="@TaskCollection" Height="450px" Width="700px">
    <GanttTaskFields Id="TaskId" Name="TaskName" StartDate="StartDate" EndDate="EndDate" Duration="Duration" Progress="Progress" Child="SubTasks" Dependency="Predecessor">
    </GanttTaskFields>
</EjsGantt>

@code{
    public List<TaskData> TaskCollection { get; set; }
    protected override void OnInitialized()
    {
        this.TaskCollection = GetTaskCollection();
    }

    public class TaskData
    {
        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 string Predecessor { get; set; }
        public List<TaskData> SubTasks { get; set; }
    }

    public static List <TaskData> GetTaskCollection() {
    List <TaskData> Tasks = new List <TaskData> () {
        new TaskData() {
            TaskId = 1,
            TaskName = "Project initiation",
            StartDate = new DateTime(2019, 04, 02),
            EndDate = new DateTime(2019, 04, 21),
            SubTasks = (new List <TaskData> () {
                new TaskData() {
                    TaskId = 2,
                    TaskName = "Identify Site location",
                    StartDate = new DateTime(2019, 04, 02),
                    Duration = "0",
                    Progress = 30,
                },
                new TaskData() {
                    TaskId = 3,
                    TaskName = "Perform soil test",
                    StartDate = new DateTime(2019, 04, 02),
                    Duration = "4",
                    Progress = 40,
                    Predecessor = "2"
                },
                new TaskData() {
                    TaskId = 4,
                    TaskName = "Soil test approval",
                    StartDate = new DateTime(2019, 04, 02),
                    Duration = "0",
                    Progress = 30,
                    Predecessor = "3"
                },
            })
        },
        new TaskData() {
            TaskId = 5,
            TaskName = "Project estimation",
            StartDate = new DateTime(2019, 04, 02),
            EndDate = new DateTime(2019, 04, 21),
            SubTasks = (new List <TaskData> () {
                new TaskData() {
                    TaskId = 6,
                    TaskName = "Develop floor plan for estimation",
                    StartDate = new DateTime(2019, 04, 04),
                    Duration = "3",
                    Progress = 30,
                    Predecessor = "4"
                },
                new TaskData() {
                    TaskId = 7,
                    TaskName = "List materials",
                    StartDate = new DateTime(2019, 04, 04),
                    Duration = "3",
                    Progress = 40,
                    Predecessor = "6"
                },
                new TaskData() {
                    TaskId = 8,
                    TaskName = "Estimation approval",
                    StartDate = new DateTime(2019, 04, 04),
                    Duration = "0",
                    Progress = 30,
                    Predecessor = "7"
                },
            })
        }
    };

    return Tasks;
}
}

The following screenshot displays the output of the above code.

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Predecessor offset with duration units

In the Gantt component, the predecessor offset can be defined with the following duration units:

  • Day
  • Hour
  • Minute

You can define an offset with various offset duration units for predecessors by using the following code example.

@using Syncfusion.EJ2.Blazor.Gantt
<EjsGantt DataSource="@TaskCollection" Height="450px" Width="900px">
    <GanttTaskFields Id="TaskId" Name="TaskName" StartDate="StartDate" EndDate="EndDate" Duration="Duration" Progress="Progress" Dependency="Predecessor" Child="SubTasks">
    </GanttTaskFields>
</EjsGantt>
@code{
    public List<TaskData> TaskCollection { get; set; }
    protected override void OnInitialized()
    {
        this.TaskCollection = GetTaskCollection();
    }

    public class TaskData
    {
        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 string Predecessor { get; set; }
        public List<TaskData> SubTasks { get; set; }
    }

    public static List <TaskData> GetTaskCollection() {
    List <TaskData> Tasks = new List <TaskData> () {
        new TaskData() {
            TaskId = 1,
            TaskName = "Project initiation",
            StartDate = new DateTime(2019, 04, 02),
            EndDate = new DateTime(2019, 04, 21),
            SubTasks = (new List <TaskData> () {
                new TaskData() {
                    TaskId = 2,
                    TaskName = "Identify Site location",
                    StartDate = new DateTime(2019, 04, 02),
                    Duration = "0",
                    Progress = 30,
                },
                new TaskData() {
                    TaskId = 3,
                    TaskName = "Perform soil test",
                    StartDate = new DateTime(2019, 04, 02),
                    Duration = "4",
                    Progress = 40,
                    Predecessor = "2FS+2d"
                },
                new TaskData() {
                    TaskId = 4,
                    TaskName = "Soil test approval",
                    StartDate = new DateTime(2019, 04, 02),
                    Duration = "0",
                    Progress = 30,
                    Predecessor = "3FF+960m"
                },
            })
        },
        new TaskData() {
            TaskId = 5,
            TaskName = "Project estimation",
            StartDate = new DateTime(2019, 04, 02),
            EndDate = new DateTime(2019, 04, 21),
            SubTasks = (new List <TaskData> () {
                new TaskData() {
                    TaskId = 6,
                    TaskName = "Develop floor plan for estimation",
                    StartDate = new DateTime(2019, 04, 04),
                    Duration = "3",
                    Progress = 30,
                },
                new TaskData() {
                    TaskId = 7,
                    TaskName = "List materials",
                    StartDate = new DateTime(2019, 04, 04),
                    Duration = "3",
                    Progress = 40,
                    Predecessor = "6SS+16h"
                },
            })
        }
    };

    return Tasks;
}
}

The following screen shot depicts the duration unit support in the predecessor offset.

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