[Solved] Filter and populate DataGridView based on ComboBox selection in Windows Forms (WinForms) Application using C# and VB.Net

I have added the Comboxbox outside of DataGridView. At Selected Index change event of Combobox i am Populating the DataGridView.

Please refer this code.

C#

Namespaces

using System.Data.SqlClient;
using System.Configuration;

Code

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        this.PopulateCombobox();
        this.dataGridView1.AllowUserToAddRows = false;
    }

    private void PopulateCombobox()
    {
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection conn = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT DISTINCT Country FROM Customers", conn))
            {
                using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                {
                    DataTable dt = new DataTable();
                    da.Fill(dt);
                    // Create a new row
                    DataRow dr = dt.NewRow();
                    dr["Country"] = "";
                    dt.Rows.InsertAt(dr, 0);
                    this.comboBox1.DisplayMember = "Country";
                    this.comboBox1.ValueMember = "Country";
                    this.comboBox1.DataSource = dt;

                }
            }
        }
    }

    private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection conn = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT ContactName ,City FROM Customers WHERE Country  = @Country OR @Country = ''", conn))
            {
                using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                {
                    cmd.Parameters.AddWithValue("@Country", this.comboBox1.SelectedValue);
                    DataTable dt = new DataTable();
                    da.Fill(dt);
                    this.dataGridView1.DataSource = dt;
                }
            }
        }
    }
}

VB

Namespaces

Imports System.Data.SqlClient
Imports System.Configuration

Code

Public Class Form1

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        Me.PopulateCombobox()
        Me.DataGridView1.AllowUserToAddRows = False
    End Sub


    Private Sub PopulateCombobox()
        Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Using conn As New SqlConnection(constr)
            Using cmd As New SqlCommand("SELECT DISTINCT Country FROM Customers", conn)
                Using da As New SqlDataAdapter(cmd)
                    Dim dt As New DataTable()
                    da.Fill(dt)
                    ' Create a new row
                    Dim dr As DataRow = dt.NewRow()
                    dr("Country") = ""
                    dt.Rows.InsertAt(dr, 0)
                    Me.comboBox1.DisplayMember = "Country"
                    Me.comboBox1.ValueMember = "Country"

                    Me.comboBox1.DataSource = dt
                End Using
            End Using
        End Using
    End Sub

    Private Sub comboBox1_SelectedIndexChanged_1(sender As System.Object, e As System.EventArgs) Handles comboBox1.SelectedIndexChanged
        Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Using conn As New SqlConnection(constr)
            Using cmd As New SqlCommand("SELECT ContactName ,City FROM Customers WHERE Country  = @Country OR @Country = ''", conn)
                Using da As New SqlDataAdapter(cmd)
                    cmd.Parameters.AddWithValue("@Country", Me.comboBox1.SelectedValue)
                    Dim dt As New DataTable()
                    da.Fill(dt)
                    Me.DataGridView1.DataSource = dt
                End Using
            End Using
        End Using
    End Sub
End Class

Database

I am using Northwind database and for more details refer the ASPSnippets article

Install Microsoft Northwind and Pubs Sample databases in SQL Server Management Studio

Screenshot