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Data Binding

The DropDownList loads the data either from local data sources or remote data services using the dataSource property. It supports the data type of array or DataManager.

The DropDownList also supports different kinds of data services such as OData, OData V4, and Web API, and data formats such as XML, JSON, and JSONP with the help of DataManager adaptors.

Fields Type Description
text string Specifies the display text of each list item.
value number or string Specifies the hidden data value mapped to each list item that should contain a unique value.
groupBy string Specifies the category under which the list item has to be grouped.
iconCss string Specifies the icon class of each list item.

When binding complex data to the DropDownList, fields should be mapped correctly. Otherwise, the selected item remains undefined.

Binding local data

Local data can be represented in two ways as described below.

1. Array of simple data

The DropDownList has support to load array of primitive data such as strings and numbers. Here, both value and text field act the same.

razor
arrayofstrings.cs
@Html.EJS().DropDownList("games").Placeholder("Select a game").PopupHeight("200px").DataSource((IEnumerable<object>)ViewBag.data).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 arrayofstrings()
        {
            ViewBag.data = new string[] { "Badminton", "Basketball", "Cricket", "Football", "Golf", "Gymnastics", "Hockey", "Tennis" };
            return View();
        }
    }
}

2. Array of JSON data

The DropDownList can generate its list items through an array of complex data. For this, the appropriate columns should be mapped to the fields property.

In the following example, Vegetable column from complex data have been mapped to the value field.

razor
arrayofobjects.cs
Vegetables.cs
@Html.EJS().DropDownList("vegetables").Placeholder("Select a Vegetables").PopupHeight("200px").DataSource((IEnumerable<object>)ViewBag.data).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings { Value = "Vegetable" }).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 arrayofobjects()
        {
            ViewBag.data = new Vegetables().VegetablesList();
            return View();
        }
    }
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace WebApplication1.Models
{
    public class Vegetables
    {
        public string Vegetable { get; set; }
        public string Category { get; set; }
        public string Id { get; set; }
        public List<Vegetables> VegetablesList()
        {
        List<Vegetables> veg = new List<Vegetables>();
        veg.Add(new Vegetables { Vegetable = "Cabbage", Category= "Leafy and Salad", Id= "item1" });
        veg.Add(new Vegetables { Vegetable = "Chickpea", Category= "Beans", Id= "item2" });
        veg.Add(new Vegetables { Vegetable = "Garlic", Category= "Bulb and Stem", Id= "item3" });
        veg.Add(new Vegetables { Vegetable = "Green bean", Category= "Beans", Id= "item4" });
        veg.Add(new Vegetables { Vegetable = "Horse gram", Category= "Beans", Id= "item5" });
        veg.Add(new Vegetables { Vegetable = "Nopal", Category= "Bulb and Stem", Id= "item6" });
        veg.Add(new Vegetables { Vegetable = "Onion", Category= "Bulb and Stem", Id= "item7" });
        veg.Add(new Vegetables { Vegetable = "Pumpkins", Category= "Leafy and Salad", Id= "item8" });
        veg.Add(new Vegetables { Vegetable = "Spinach", Category= "Leafy and Salad", Id= "item9" });
        veg.Add(new Vegetables { Vegetable = "Wheat grass", Category= "Leafy and Salad", Id= "item10" });
        veg.Add(new Vegetables { Vegetable = "Yarrow", Category = "Leafy and Salad", Id = "item11" });
         return veg;
        }
    }
}

3. Array of Complex data

The DropDownList can generate its list items through an array of complex data. For this, the appropriate columns should be mapped to the fields property.

In the following example, Code.Id column and Country.CountrtyId column from complex data have been mapped to the value field and text field, respectively.

razor
complexdata.cs
Complex.cs
@Html.EJS().DropDownList("games").Placeholder("Select a game").PopupHeight("200px").DataSource((IEnumerable<Object>)ViewBag.data).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings { Text = "Country.CountryId", Value = "Code.Id" }).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 complexdata()
        {
            ViewBag.data = new Complex().GetData();
            return View();
        }
    }
}
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace WebApplication1.Models
{
    public class Code
    {
        public string Id { get; set; }
    }

    public class Country
    {
        public string CountryId { get; set; }
    }
    public class Complex
    {
        public Country Country { get; set; }
        public Code Code { get; set; }
        public List<Complex> GetData()
        {
            List<Complex> data = new List<Complex>();
            data.Add(new Complex() { Country = new Country() { CountryId = "Australia"  }, Code = new Code() { Id = "AU" } });
            data.Add(new Complex() { Country = new Country() { CountryId = "Bermuda" }, Code = new Code() { Id = "BM" } });
            data.Add(new Complex() { Country = new Country() { CountryId = "Canada" }, Code = new Code() { Id = "CA" } });
            data.Add(new Complex() { Country = new Country() { CountryId = "Cameroon" }, Code = new Code() { Id = "CM" } });
            data.Add(new Complex() { Country = new Country() { CountryId = "Denmark" }, Code = new Code() { Id = "DK" } });
            data.Add(new Complex() { Country = new Country() { CountryId = "France" }, Code = new Code() { Id = "FR" } });
            return data;
        }
    }
}

Binding remote data

The DropDownList supports retrieval of data from remote data services with the help of DataManager control. The Query property is used to fetch data from the database and bind it to the DropDownList.

The following sample displays the first 6 contacts from Customers table of the Northwind Data Service.

razor
remotedata.cs
@Html.EJS().DropDownList("customers").Placeholder("Select a customer").PopupHeight("200px").DataSource(dataManger =>
            dataManger.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()
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 remotedata()
        {
            return View();
        }
    }
}

Bind to URL Adaptor

The DropDownList supports retrieval of data from URL adaptor.

razor
urldata.cs
@Html.EJS().DropDownList("games").Placeholder("Select a Country").PopupHeight("200px").DataSource(dataManger =>
    dataManger.Url("/ComboBox/UrlDatasource").Adaptor("UrlAdaptor").CrossDomain(true)).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings
    {
        Value = "ShipCountry"
    }).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 Index()
        {
            return View();
        }
        public ActionResult UrlDatasource([FromBody]Data dm)
        {
            var val = OrdersDetails.GetAllRecords();
            var Data = val.ToList();
            var count = val.Count();
            if (dm.where != null)
            {
                Data = (from cust in Data
                        where cust.ShipCountry.ToLower().StartsWith(dm.@where[0].value.ToString())
                        select cust).ToList();
            }
            if (dm.take != 0)
                Data = Data.Take(dm.take).ToList();
            return Json(Data);
        }


        public class Data
        {
            public int take { get; set; }
            public List<Wheres> where { get; set; }
        }

        public class Wheres
        {
            public string field { get; set; }
            public bool ignoreAccent { get; set; }

            public bool ignoreCase { get; set; }

            public bool isComplex { get; set; }

            public string value { get; set; }
            public string Operator { get; set; }

        }
        public class OrdersDetails
        {
            public static List<OrdersDetails> order = new List<OrdersDetails>();
            public OrdersDetails()
            {

            }
            public OrdersDetails(int OrderID, string CustomerId, int EmployeeId, double Freight, bool Verified, DateTime OrderDate, string ShipCity, string ShipName, string ShipCountry, DateTime ShippedDate, string ShipAddress)
            {
                this.OrderID = OrderID;
                this.CustomerID = CustomerId;
                this.EmployeeID = EmployeeId;
                this.Freight = Freight;
                this.ShipCity = ShipCity;
                this.Verified = Verified;
                this.OrderDate = OrderDate;
                this.ShipName = ShipName;
                this.ShipCountry = ShipCountry;
                this.ShippedDate = ShippedDate;
                this.ShipAddress = ShipAddress;
            }
            public static List<OrdersDetails> GetAllRecords()
            {
                if (order.Count() == 0)
                {
                    int code = 10000;
                    for (int i = 1; i < 10; i++)
                    {
                        order.Add(new OrdersDetails(code + 1, "ALFKI", i + 0, 2.3 * i, false, new DateTime(1991, 05, 15), "Berlin", "Simons bistro", "Denmark", new DateTime(1996, 7, 16), "Kirchgasse 6"));
                        order.Add(new OrdersDetails(code + 2, "ANATR", i + 2, 3.3 * i, true, new DateTime(1990, 04, 04), "Madrid", "Queen Cozinha", "Brazil", new DateTime(1996, 9, 11), "Avda. Azteca 123"));
                        order.Add(new OrdersDetails(code + 3, "ANTON", i + 1, 4.3 * i, true, new DateTime(1957, 11, 30), "Cholchester", "Frankenversand", "Germany", new DateTime(1996, 10, 7), "Carrera 52 con Ave. Bolívar #65-98 Llano Largo"));
                        order.Add(new OrdersDetails(code + 4, "BLONP", i + 3, 5.3 * i, false, new DateTime(1930, 10, 22), "Marseille", "Ernst Handel", "Austria", new DateTime(1996, 12, 30), "Magazinweg 7"));
                        order.Add(new OrdersDetails(code + 5, "BOLID", i + 4, 6.3 * i, true, new DateTime(1953, 02, 18), "Tsawassen", "Hanari Carnes", "Switzerland", new DateTime(1997, 12, 3), "1029 - 12th Ave. S."));
                        code += 5;
                    }
                }
                return order;
            }

            public int? OrderID { get; set; }
            public string CustomerID { get; set; }
            public int? EmployeeID { get; set; }
            public double? Freight { get; set; }
            public string ShipCity { get; set; }
            public bool Verified { get; set; }
            public DateTime OrderDate { get; set; }

            public string ShipName { get; set; }

            public string ShipCountry { get; set; }

            public DateTime ShippedDate { get; set; }
            public string ShipAddress { get; set; }
        }
    }
}

Web API Adaptor

Use the WebApiAdaptor to bind DropDownList with Web API created using OData.

razor
webapi.cs
<div id='web-data' class='col-lg-6' style='padding-top:15px'>
    <div class='content'>
            @Html.EJS().DropDownList("games").DataSource(dataManger =>
            dataManger.Url("/api/Dropdownlist/").Adaptor("WebApiAdaptor")).Render()
    </div>
</div>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using WebApplication1.Models;

namespace WebApplication1.Controllers
{
    [Route("api/[controller]")]
    public class DropdownlistController : Controller
    {
        List<string> game = new List<string>();
        [HttpGet]
        public List<string> Get()
        {
            game.Add("Badminton");
            game.Add("Basketball");
            game.Add("Cricket");
            game.Add("Golf");
            game.Add("Gymnastics");
            game.Add("Tennis");
            game.Add("Hockey");
            return game;
        }
    }
}

Binding with OData services

OData is a standardized protocol for creating and consuming data. You can retrieve data from OData service using the DataManager.

The following example for remote data binding using OData service.

razor
odata.cs
<div id='o-data' class='col-lg-6' style='padding-top:15px'>
    <div class='content'>
        @Html.EJS().DropDownList("customers").Placeholder("Select a customer").PopupHeight("200px").DataSource(dataManger =>
            dataManger.Url("https://js.syncfusion.com/ejServices/Wcf/Northwind.svc/Orders/").Adaptor("ODataAdaptor").CrossDomain(true)).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings
            {
                Value = "CustomerID"
            }).Query("new ej.data.Query().select(['CustomerID']).take(7)").Render()
    </div>
</div>
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 odata()
        {
            return View();
        }
    }
}

Offline mode

To avoid post back for every action, set the DropDownList to load all data on initialization and make the actions process in client-side. To enable this behavior, use the Offline property of DataManager.

The following example for remote data binding and enabled offline mode.

razor
offline.cs
<div id='o-data' class='col-lg-6' style='padding-top:15px'>
    <div class='content'>
        @Html.EJS().DropDownList("customers").Placeholder("Select a customer").PopupHeight("200px").DataSource(dataManger =>
            dataManger.Url("http://js.syncfusion.com/ejServices/Wcf/Northwind.svc/Orders/").Offline(true).Adaptor("ODataAdaptor").CrossDomain(true)).Fields(new Syncfusion.EJ2.DropDowns.DropDownListFieldSettings
            {
                Value = "CustomerID"
            }).Query("new ej.data.Query().select(['CustomerID']).take(7)").Render()
    </div>
</div>
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 offline()
        {
            return View();
        }
    }
}

See Also