Whrn I Select One Combo Box Country Not Change State In Another Combo Box.. Pls Help Me

Question

2.00/5 (2 votes)

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C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace country_state_city
{
    public partial class Form1 : Form
    {

        SqlConnection con = new SqlConnection(*************);
        
        public Form1()
        {
            InitializeComponent();
           
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            
            SqlCommand cmd = new SqlCommand("select * from Country", con);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();
            da.Fill(ds);
            comboBox1.SelectedIndex = -1;
            comboBox1.DataSource = ds.Tables[0];
           
            comboBox1.DisplayMember = "County";
            comboBox1.ValueMember = "Countryid";
           
            
        }

        private void button1_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            //MessageBox.Show(comboBox1.SelectedIndex.ToString());
            if (comboBox1.SelectedIndex >= 0)
            {

                SqlDataAdapter da = new SqlDataAdapter("Select * From CountryState Where CountryId='" + comboBox1.SelectedValue + "'", con);
                DataSet ds = new DataSet();
                da.Fill(ds);

                comboBox2.DataSource = ds.Tables[0];
                comboBox2.DisplayMember = "State";
                comboBox2.ValueMember = "StateId";
            }
            
        }

        

        private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (comboBox2.SelectedIndex > 0)
            {

                SqlDataAdapter da = new SqlDataAdapter("Select * From StateCity Where StateId='" + comboBox2.SelectedValue + "'", con);
                DataSet ds = new DataSet();
                da.Fill(ds);

                comboBox3.DataSource = ds.Tables[0];
                comboBox3.DisplayMember = "City";
                comboBox3.ValueMember = "CityId";
            }
        }
    }
}

Posted 1-Jul-14 23:42pm

Member 10918596

Updated 2-Jul-14 0:23am

CHill60

v2

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Murugesan22 3-Jul-14 5:35am

try this, If i am not wrong

Can you please add form load event in if(!ispostback)

Because everytime load form means it give countryid is zero thats why you cant get correct value in state

I will you post same content with ispostback option

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CHill60 · Answer 1 · 2014-07-02T03:30:00

Couple of things to consider here ...

1. Your comboBox1_SelectedIndexChanged event is being fired as the comboBox is being populated, and the SelectedIndex equals zero at that point. So processing is dropping into your code, but before there is anything actually selected.

One way around this is to unsubscribe from the comboBox1_SelectedIndexChanged event while you are populating the comboBox. e.g. like this

C#

this.comboBox1.SelectedIndexChanged -= new System.EventHandler(this.comboBox1_SelectedIndexChanged);
SqlCommand cmd = new SqlCommand("select * from Country", con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();

Then after you have populated the comboBox, you can subscribe to the event, and force a selection to happen e.g.

C#

comboBox1.SelectedIndex = -1;
this.comboBox1.SelectedIndexChanged += new System.EventHandler(this.comboBox1_SelectedIndexChanged);
comboBox1.SelectedIndex = 0;

2. Your comboBox1 is going to populated with numbers because you have used

C#

comboBox1.DisplayMember = "County";

- there is no such column, it should be Country

3. Never use string concatenation to build your sql statements like this

C#

SqlDataAdapter da = new SqlDataAdapter("Select * From CountryState Where CountryId='" + comboBox1.SelectedValue + "'", con);

You leave yourself wide open to SQL Injection attacks[^] - use parameterized queries instead e.g.

C#

SqlCommand cmd = new SqlCommand("Select * from StateCity Where StateId=@id", con);
cmd.Parameters.AddWithValue("@id", comboBox2.SelectedValue);
SqlDataAdapter da = new SqlDataAdapter(cmd);

4. You need to get into the habit of using some best practices such as Try-Catch blocks[^] and using statements[^]

CB Sharma · Answer 2 · 2014-07-02T00:01:00

Hello

See the below code posted by me

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace country_state_city
{
    public partial class Form1 : Form
    {
        SqlConnection con = new SqlConnection("*************");
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            SqlCommand cmd = new SqlCommand("select * from Country", con);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();
            da.Fill(ds);

            comboBox1.DataSource = ds.Tables[0];

            comboBox1.DisplayMember = "County";
            comboBox1.ValueMember = "Countryid";
            comboBox1.SelectedIndex = 0;
        }
        private void button1_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            MessageBox.Show(comboBox1.SelectedIndex.ToString());
            if (comboBox1.SelectedIndex >= 0)
            {
                SqlDataAdapter da = new SqlDataAdapter("Select * From CountryState Where CountryId='" + comboBox1.SelectedValue + "'", con);
                DataSet ds = new DataSet();
                da.Fill(ds);

                comboBox2.DataSource = ds.Tables[0];
                comboBox2.DisplayMember = "State";
                comboBox2.ValueMember = "StateId";
                comboBox2.SelectedIndex = 0;
            }
        }
        private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (comboBox2.SelectedIndex >= 0)
            {
                SqlDataAdapter da = new SqlDataAdapter("Select * From StateCity Where StateId='" + comboBox2.SelectedValue + "'", con);
                DataSet ds = new DataSet();
                da.Fill(ds);
                comboBox3.DataSource = ds.Tables[0];
                comboBox3.DisplayMember = "City";
                comboBox3.ValueMember = "CityId";
                comboBox3.SelectedIndex = 0;
            }
        }
    }
}

Whrn I Select One Combo Box Country Not Change State In Another Combo Box.. Pls Help Me

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