Show related data from one Combobox to another

Satyapriyanayak
Posted by Satyapriyanayak under C# category on | Points: 40 | Views : 1204
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.OleDb;
namespace Combobox
{
public partial class Form1 : Form
{
string ConnectionString = System.Configuration.ConfigurationSettings.AppSettings["dsn"];
OleDbCommand com;
OleDbDataAdapter oda;
DataSet ds;
string str;
public Form1()
{
InitializeComponent();
}

private void Form1_Load(object sender, EventArgs e)
{
comboBox1.Text = "Choose CourseID";
comboBox1.Items.Add("Choose CourseID");
OleDbConnection con = new OleDbConnection(ConnectionString);
con.Open();
str = "select * from Courses";
com = new OleDbCommand(str, con);
OleDbDataReader reader = com.ExecuteReader();
while (reader.Read())
{
comboBox1.Items.Add(reader["CourseID"]);
}
}

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
comboBox2.Items.Clear();
OleDbConnection con = new OleDbConnection(ConnectionString);
con.Open();
str = "select * from Students where CourseID='" + comboBox1.Text.Trim() + "'";
com = new OleDbCommand(str, con);
OleDbDataReader reader = com.ExecuteReader();
while (reader.Read())
{
comboBox2.Items.Add(reader["FirstName"].ToString());
}
con.Close();
reader.Close();
}
}
}

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