Bind DropDownList using simple user defined method in ASP.Net

Introduction:

In this article, I will explain how to bind DropDownList using a simple user-defined method in ASP.Net.

Objective:

  1. Bind DropDownList using simple user defined method in ASP.Net
  2. User defined method should accept collection (e.g: List<Employee> or List<User> or List<Role> etc)
  3. User defined method should accept DataTable as well

I created a class called CommonUI.cs with the FillDropDown(...) method, as shown below:

using System;
using System.Collections.Generic;
using System.Web.UI.WebControls;
namespace ASPDemos
{ 
    public class CommonUI
    {
        /// <summary>
        /// Binds list to DropDownList control.
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="dropDownList"></param>
        /// <param name="list"></param>
        /// <param name="dataTextField"></param>
        /// <param name="dataValueField"></param>
        public static void FillDropDown<T>(DropDownList dropDownList, List<T> list, string dataTextField, string dataValueField)
        {
            if (list != null &amp;&amp; list.Count > 0)
            {
                dropDownList.DataSource = list;
                dropDownList.DataTextField = dataTextField;
                dropDownList.DataValueField = dataValueField;
                dropDownList.DataBind();
            }
            dropDownList.Items.Insert(0, (new ListItem("Select", "-1")));
        }
    }
}

FillDropDown(...) method accepts 4 parameters:

  1. dropDownList - DropDownList ID for which you are binding
  2. list - It may be List<Employee>, List<User>, List<Role>, etc.
  3. dataTextField - Gets or sets the field of the data source that provides the text of the each list item
  4. dataValueField - Gets or sets the field of the data source that provides the value of each list item

Assume we have a class called Role.cs, as shown below:

Role.cs:

using System;
using System.Collections.Generic;
namespace ASPDemos
{
    public class Role
    {
        public int RoleID { get; set; }
        public string RoleName { get; set; }

        /// <summary>
        /// Get list of User Roles.
        /// </summary>
        /// <returns>List</returns>
        public static List<Role> GetRoles()
        {
            var lstRole = new List<Role>{
                new Role { RoleID = 1, RoleName = "User" },
                new Role { RoleID = 2, RoleName = "Admin" },
                new Role { RoleID = 3, RoleName = "Super Admin" }
            };
            return lstRole;
        }
    }
}

Bind User Role list to DropDownList:

Now bind list of roles to DropDownList as shown below:

CommonUI.FillDropDown(ddlRole, Role.GetRoles(), "RoleName", "RoleID");

Here we are accessing FillDropDown method directly with CommonUI class name. Because it is static method. Role.GetRoles() method returns List<Role>.

Bind User Role DataTable to DropDownList:

Assume that we have a DataTable called dtRole. Now bind this data table to DropDownList, as shown below:

CommonUI.FillDropDown(ddlRole, dtRole.Rows.Cast<DataRow>().ToList(), "RoleName", "RoleID");

Here dtRole.Rows.Cast<DataRow>().ToList() returns List<DataRow>.

DataTable requires System.Data namespace, .ToList() method requires System.Linq namespace.

Full Source Code:

DropDownListDemo.aspx:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="DropDownListDemo.aspx.cs" Inherits="ASPDemos.DropDownListDemo" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Bind DropDownList using simple user defined method in ASP.Net</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="ddlRole" runat="server"></asp:DropDownList>
    </div>
    </form>
</body>
</html>

DropDownListDemo.aspx.cs:

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Web.UI.WebControls;

namespace ASPDemos
{
    public partial class DropDownListFillMethod : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                CommonUI.FillDropDown(ddlRole, Role.GetRoles(), "RoleName", "RoleID");

                // Uncomment below code when you pass DataTable into FillDropDown method.
                //DataTable dtRole = new DataTable();
                //CommonUI.FillDropDown(ddlRole, dtRole.Rows.Cast<DataRow>().ToList(), "RoleName", "RoleID");
            }
        }
    }

    public class Role
    {
        public int RoleID { get; set; }
        public string RoleName { get; set; }

        /// <summary>
        /// Get list of User Roles.
        /// </summary>
        /// <returns>List</returns>
        public static List<Role> GetRoles()
        {
            var lstRole = new List<Role>{
                new Role { RoleID = 1, RoleName = "User" },
                new Role { RoleID = 2, RoleName = "Admin" },
                new Role { RoleID = 3, RoleName = "Super Admin" }
            };
            return lstRole;
        }
    }

    public class CommonUI
    {
        /// <summary>
        /// Binds list to DropDownList control.
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="dropDownList"></param>
        /// <param name="list"></param>
        /// <param name="DataTextField"></param>
        /// <param name="DataValueField"></param>
        public static void FillDropDown<T>(DropDownList dropDownList, List<T> list, string DataTextField, string DataValueField)
        {
            if (list != null &amp;&amp; list.Count > 0)
            {
                dropDownList.DataSource = list;
                dropDownList.DataTextField = DataTextField;
                dropDownList.DataValueField = DataValueField;
                dropDownList.DataBind();
            }
            // Insert 'Select' option at '0' index.
            dropDownList.Items.Insert(0, (new ListItem("Select", "-1")));
        }
    }
}

Output:

  • Created
    Nov 18, 2014
  • Updated
    Oct 03, 2020
  • Views
    3,919
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