Working With DropDownList SelectedIndexChanged Event

Working with DropDownList SelectedIndex Changed Event

Let's make a scenario to use a SelectedIndexChanged event of a dropdownlist control by binding it with a database.

Create a Table

Here we are taking four attributes. 

 

Add Content

Connection String

Setting Connection String in the web.config file. 

Front-End

Here is how our aspx page looks like. 

Code

Find the aspx.cs code below.

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace StateManagement
{
    public partial class WebForm2 : System.Web.UI.Page
    {

        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["dbconnection"].ConnectionString);
        protected void Page_Load(object sender, EventArgs e)
        {

            if (!IsPostBack)
            {
                String strQuery = "SELECT distinct (City) FROM UserDetails";

                SqlCommand cmd = new SqlCommand();
                cmd.CommandType = CommandType.Text;
                cmd.CommandText = strQuery;
                cmd.Connection = con;
                try
                {
                    con.Open();
                    DropDownList1.DataSource = cmd.ExecuteReader();
                    DropDownList1.DataTextField = "City";
                    DropDownList1.DataValueField = "City";
                    DropDownList1.DataBind();
                    //   DropDownList2.SelectedIndex = 1;
                }
                catch (Exception ex)
                {
                    throw ex;
                }
                finally
                {
                    con.Close();
                    //  con.Dispose();
                }
            }

        }

        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {

            String strQuery = "SELECT distinct (Designation) FROM UserDetails";

            SqlCommand cmd = new SqlCommand();
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = strQuery;
            cmd.Connection = con;
            try
            {
                con.Open();
                DropDownList2.DataSource = cmd.ExecuteReader();
                DropDownList2.DataTextField = "Designation";
                DropDownList2.DataValueField = "Designation";
                DropDownList2.DataBind();
                // DropDownList2.SelectedIndex = 1;
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                con.Close();
                con.Dispose();
            }

        }

        protected void Button2_Click(object sender, EventArgs e) //Gridview binding
        {
            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["dbconnection"].ConnectionString);
            SqlCommand cmd = new SqlCommand("select * from UserDetails where City = '" + DropDownList1.SelectedValue + "' and Designation='"+DropDownList2.SelectedValue+"'" , con);
            SqlDataAdapter Adpt = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            Adpt.Fill(dt);
            GridView1.DataSource = dt;
            GridView1.DataBind();
        }

        protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
        {
            //code for  DropDownList2_SelectedIndexChanged
        }

         }
}

Output

Select the City DropDownList.

 

Select the Designation DropDownList.

 

 

Click the Search button to display details in the GridView. 

 

Summary

Great! We have implemented binding with a DropDownlist, worked with the SelectedIndexChanged event of DropDownList and GridView binding.

Thanks.