Working With DropDownList SelectedIndexChanged Event

In this article we will learn how to bind data with DropDownList thereby working with the 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.
  1. using System;  
  2. using System.Collections.Generic;  
  3. using System.Data;  
  4. using System.Data.SqlClient;  
  5. using System.Configuration;  
  6. using System.Web;  
  7. using System.Web.UI;  
  8. using System.Web.UI.WebControls;  
  9.   
  10. namespace StateManagement  
  11. {  
  12.     public partial class WebForm2 : System.Web.UI.Page  
  13.     {  
  14.           
  15.         SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["dbconnection"].ConnectionString);  
  16.         protected void Page_Load(object sender, EventArgs e)  
  17.         {  
  18.             
  19.             if (!IsPostBack)  
  20.             {  
  21.                 String strQuery = "SELECT distinct (City) FROM UserDetails";  
  22.   
  23.                 SqlCommand cmd = new SqlCommand();  
  24.                 cmd.CommandType = CommandType.Text;  
  25.                 cmd.CommandText = strQuery;  
  26.                 cmd.Connection = con;  
  27.                 try  
  28.                 {  
  29.                     con.Open();  
  30.                     DropDownList1.DataSource = cmd.ExecuteReader();  
  31.                     DropDownList1.DataTextField = "City";  
  32.                     DropDownList1.DataValueField = "City";  
  33.                     DropDownList1.DataBind();  
  34.                     //   DropDownList2.SelectedIndex = 1;  
  35.                 }  
  36.                 catch (Exception ex)  
  37.                 {  
  38.                     throw ex;  
  39.                 }  
  40.                 finally  
  41.                 {  
  42.                     con.Close();  
  43.                     //  con.Dispose();  
  44.                 }  
  45.             }  
  46.              
  47.         }  
  48.   
  49.         protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)  
  50.         {  
  51.               
  52.             String strQuery = "SELECT distinct (Designation) FROM UserDetails";  
  53.   
  54.             SqlCommand cmd = new SqlCommand();  
  55.             cmd.CommandType = CommandType.Text;  
  56.             cmd.CommandText = strQuery;  
  57.             cmd.Connection = con;  
  58.             try  
  59.             {  
  60.                 con.Open();  
  61.                 DropDownList2.DataSource = cmd.ExecuteReader();  
  62.                 DropDownList2.DataTextField = "Designation";  
  63.                 DropDownList2.DataValueField = "Designation";  
  64.                 DropDownList2.DataBind();  
  65.                 // DropDownList2.SelectedIndex = 1;  
  66.             }  
  67.             catch (Exception ex)  
  68.             {  
  69.                 throw ex;  
  70.             }  
  71.             finally  
  72.             {  
  73.                 con.Close();  
  74.                 con.Dispose();  
  75.             }            
  76.   
  77.         }        
  78.   
  79.         protected void Button2_Click(object sender, EventArgs e) //Gridview binding  
  80.         {  
  81.             SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["dbconnection"].ConnectionString);  
  82.             SqlCommand cmd = new SqlCommand("select * from UserDetails where City = '" + DropDownList1.SelectedValue + "' and Designation='"+DropDownList2.SelectedValue+"'" , con);  
  83.             SqlDataAdapter Adpt = new SqlDataAdapter(cmd);  
  84.             DataTable dt = new DataTable();  
  85.             Adpt.Fill(dt);  
  86.             GridView1.DataSource = dt;  
  87.             GridView1.DataBind();  
  88.         }  
  89.   
  90.         protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)  
  91.         {  
  92.             //code for  DropDownList2_SelectedIndexChanged  
  93.         }       
  94.   
  95.          }  
  96. }

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.