Cascading Combobox in Windows Application using C#

In this tutorial I’ll show you how to use cascading combo boxes in windows application using C#, where we take two combo box and bind it and cascade it.

INITIAL CHAMBER:

Step1) Open Your Visual Studio 2010, Go to File - -> New - -> Projects - -> Under Visual C#  - -> Windows.

You can change the name of the project and you can browse your project to different location too. And then press – OK.

Step2) In Solution Explorer you get your Project, Add Service Based Database. – By going to your Project -- > Right Click and Add New Item - -> Service Based Database.

DATABASE CHAMBER:

Step3)  Get to your Database [Database.mdf], we will create two table - -> tbl_country and tbl_state. Go to the database.mdf - -> Table - -> Add New table, design your table like this:

Tbl_country:

Tbl_state:

DESIGN CHAMBER:

Step5)  Now open your Form1.cs [Design] file, where we create our design for Cascading ComboBox.

We will drag two ComboBox from tool box to Form1.cs [Design], you will see your Form look like this.

Form1.cs [Design]:

CODE CHAMBER:

Right Click on the blank part of Form1.cs  - -> View Code. You will see you are entered in the code part of the form. Write Below code.  And then Press F5 to run the project.

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Data.SqlClient;

namespace cascadingdropdownlist

{

   public partial class Form1 : Form

   {

       SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database1.mdf;Integrated Security=True;User Instance=True");

       DataRow dr;

       public Form1()

       {

           InitializeComponent();

           refreshdata();

       }

       public void refreshdata()

       {

         

          

           con.Open();

           SqlCommand cmd = new SqlCommand("select * from tbl_country", con);

           SqlDataAdapter sda = new SqlDataAdapter(cmd);

           DataTable dt = new DataTable();

           sda.Fill(dt);

           con.Close();

           dr = dt.NewRow();

           dr.ItemArray = new object[] { 0, "--Select Country--" };

           dt.Rows.InsertAt(dr, 0);

           comboBox1.ValueMember = "countryid";

           comboBox1.DisplayMember = "countryname";

           comboBox1.DataSource = dt;    

  

       }

       private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)

       {

           if (comboBox1.SelectedValue.ToString()!= null)

           {

               int countryid = Convert.ToInt32(comboBox1.SelectedValue.ToString());

               refreshstate(countryid);

               

           }

       }

           public void refreshstate(int countryid)

           {

           

           con.Open();

           SqlCommand cmd = new SqlCommand("select * from tbl_state where countryid= @countryid", con);

           cmd.Parameters.AddWithValue("countryid", countryid);

           SqlDataAdapter sda = new SqlDataAdapter(cmd);

           DataTable dt = new DataTable();

           sda.Fill(dt);

           con.Close();

           dr = dt.NewRow();

           dr.ItemArray = new object[] { 0, "--Select State--" };

           dt.Rows.InsertAt(dr, 0);

        

           comboBox2.ValueMember = "stateid";

           comboBox2.DisplayMember = "statename";

           comboBox2.DataSource = dt;

       }

   }

}

OUTPUT CHAMBER:

We are selecting Country as India from the first Combo box, the state combo box will show only the state relevant to India.

Hope you like this. Thank you for Reading. Have a good day.