Filtering
21 Feb 202413 minutes to read
The DropDownList has built-in support to filter data items when allowFiltering is enabled. The filter operation starts as soon as you start typing characters in the search box.
To display the filtered items in the popup, filter the required data and return it to the DropDownList via updateData method by using the filtering event.
The following sample illustrates how to query the data source and pass the data to the DropDownList through the updateData method in filtering event.
@Html.EJS().DropDownList("country").Placeholder("Select a COuntry").PopupHeight(
"230px").DataSource((IEnumerable<object>)ViewBag.data).AllowFiltering(true).Filtering("onfiltering").Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings { Value = "Name" }).Render()
<script>
function onfiltering(e) {
var query = new ej.data.Query();
query = (e.text !== '') ? query.where('Name', 'startswith', e.text, true) : query;
e.updateData(@Html.Raw(JsonConvert.SerializeObject(ViewBag.data)), query)
}
</script>using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
namespace WebApplication1.Models
{
public class Countries
{
public string Name { get; set; }
public string Code { get; set; }
public List<Countries> CountriesList()
{
List<Countries> country = new List<Countries>();
country.Add(new Countries { Name = "Australia", Code = "AU" });
country.Add(new Countries { Name = "Bermuda", Code = "BM" });
country.Add(new Countries { Name = "Canada", Code = "CA" });
country.Add(new Countries { Name = "Cameroon", Code = "CM" });
country.Add(new Countries { Name = "Denmark", Code = "DK" });
country.Add(new Countries { Name = "France", Code = "FR" });
country.Add(new Countries { Name = "Finland", Code = "FI" });
country.Add(new Countries { Name = "Germany", Code = "DE" });
country.Add(new Countries { Name = "Greenland", Code = "GL" });
country.Add(new Countries { Name = "Hong Kong", Code = "HK" });
country.Add(new Countries { Name = "India", Code = "IN" });
country.Add(new Countries { Name = "Italy", Code = "IT" });
country.Add(new Countries { Name = "Japan", Code = "JP" });
country.Add(new Countries { Name = "Mexico", Code = "MX" });
country.Add(new Countries { Name = "Norway", Code = "NO" });
country.Add(new Countries { Name = "Poland", Code = "PL" });
country.Add(new Countries { Name = "Switzerland", Code = "CH" });
country.Add(new Countries { Name = "United Kingdom", Code = "GB" });
country.Add(new Countries { Name = "United States", Code = "US" });
return country;
}
}
}Limit the minimum filter character
When filtering the list items, you can set the limit for character count to raise remote request and fetch filtered data on the DropDownList. This can be done by manual validation within the filter event handler.
In the following example, the remote request does not fetch the search data until the search key contains three characters.
@Html.EJS().DropDownList("customers").Placeholder("Select a customer").Filtering("onfiltering").AllowFiltering(true).PopupHeight("200px").DataSource(obj => obj.Url("https://services.odata.org/V4/Northwind/Northwind.svc/").Adaptor(
"ODataV4Adaptor").CrossDomain(true)).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings { Text = "ContactName", Value = "CustomerID" }).Query("new ej.data.Query().from('Customers').select(['ContactName', 'CustomerID']).take(6)").Render()
<script>
function onfiltering(e) {
var CBObj = document.getElementById("customers").ej2_instances[0];
// load overall data when search key empty.
if (e.text == '' && e.text.length < 3) {
e.updateData(CBObj.dataSource);
}
let query = new ej.data.Query().from('Customers').select(['ContactName', 'CustomerID']).take(6);
query = (e.text !== '' && e.text.length >= 3) ? query.where('ContactName', 'startswith', e.text, true) : query;
e.updateData(CBObj.dataSource, query);
}
</script>using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using WebApplication1.Models;
namespace WebApplication1.Controllers
{
public class DropDownListController : Controller
{
public IActionResult filteringlimit()
{
return View();
}
}
}Change the filter type
While filtering, you can change the filter type to contains, startsWith, or endsWith for string type within the filter event handler.
In the following examples, data filtering is done with endsWith type.
@Html.EJS().DropDownList("customers").Placeholder("Select a customer").AllowFiltering(true).Filtering("onfiltering").PopupHeight("200px").DataSource(obj => obj.Url("https://services.odata.org/V4/Northwind/Northwind.svc/").Adaptor(
"ODataV4Adaptor").CrossDomain(true)).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings { Text = "ContactName", Value = "CustomerID" }).Query("new ej.data.Query().from('Customers').select(['ContactName', 'CustomerID']).take(6)").Render()
<script>
function onfiltering(e) {
var CBObj = document.getElementById("customers").ej2_instances[0];
// load overall data when search key empty.
if (e.text == '')
e.updateData(CBObj.dataSource);
else {
var query = new ej.data.Query().from('Customers').select(['ContactName', 'CustomerID']).take(6);
query = (e.text !== '') ? query.where('ContactName', 'endswith', e.text, true) : query;
e.updateData(CBObj.dataSource, query);
}
}
</script>using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using WebApplication1.Models;
namespace WebApplication1.Controllers
{
public class DropDownListController : Controller
{
public ActionResult filtertype()
{
return View();
}
}
}Case sensitive filtering
Data items can be filtered either with or without case sensitivity using the DataManager. This can be done by passing the fourth optional parameter of the where clause.
@Html.EJS().DropDownList("customers").Placeholder("Select a customer").Filtering("onfiltering").AllowFiltering(true).PopupHeight("200px").DataSource(obj => obj.Url("https://services.odata.org/V4/Northwind/Northwind.svc/").Adaptor(
"ODataV4Adaptor").CrossDomain(true)).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings { Text = "ContactName", Value = "CustomerID" }).Query("new ej.data.Query().from('Customers').select(['ContactName', 'CustomerID']).take(6)").Render()
<script>
function onfiltering(e) {
var CBObj = document.getElementById("customers").ej2_instances[0];
// load overall data when search key empty.
if (e.text == '')
e.updateData(CBObj.dataSource);
else {
var query = new ej.data.Query().from('Customers').select(['ContactName', 'CustomerID']).take(6);
query = (e.text !== '') ? query.where('ContactName', 'startswith', e.text, false) : query;
e.updateData(CBObj.dataSource, query);
}
}
</script>using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using WebApplication1.Models;
namespace WebApplication1.Controllers
{
public class DropDownListController : Controller
{
public ActionResult casesensitive()
{
return View();
}
}
}Diacritics Filtering
DropDownList supports diacritics filtering which will ignore the diacritics and makes it easier to filter the results in international characters lists when the ignoreAccent is enabled.
@Html.EJS().DropDownList("list").DataSource((string[])ViewBag.data).Placeholder("e.g: aero").IgnoreAccent(true).AllowFiltering(true).Render()using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using WebApplication1.Models;
namespace WebApplication1.Controllers
{
public class DropDownListController : Controller
{
public ActionResult diacritics()
{
ViewBag.data = new string[] { "Aeróbics", "Aeróbics en Agua", "Aerografía", "Aeromodelaje", "Águilas", "Ajedrez", "Ala Delta", "Álbumes de Música","Alusivos", "Análisis de Escritura a Mano" };
return View();
}
}
}