Cascading (Dependent) multiple DataGridViews in Windows Application using C# and VB.Net

Hi RPA,

Check this example. Now please take its reference and correct your code.

Database

For this example I have used three tables Countries, States and Cities that you can download using the link given below.

Download SQL file

Form Design

Namespaces

C#

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

VB.Net

Imports System.Configuration
Imports System.Data.SqlClient

Code

C#

public Form1()
{
    InitializeComponent();
    dgCountries.DataSource = GetData("SELECT CountryId,CountryName FROM Countries");
}

private void dgCountries_CellClick(object sender, DataGridViewCellEventArgs e)
{
    if (e.RowIndex > -1)
    {
        int countryId = Convert.ToInt32(dgCountries.CurrentRow.Cells[0].Value);
        dgStates.DataSource = GetData("SELECT StateId,StateName FROM States WHERE CountryId = " + countryId);
    }
}

private void dgStates_CellClick(object sender, DataGridViewCellEventArgs e)
{
    if (e.RowIndex > -1)
    {
        int stateId = Convert.ToInt32(dgStates.CurrentRow.Cells[0].Value);
        dgCities.DataSource = GetData("SELECT CityId,CityName FROM Cities WHERE StateId = " + stateId);
    }
}

private DataTable GetData(string query)
{
    string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    SqlCommand cmd = new SqlCommand(query);
    using (SqlConnection con = new SqlConnection(conString))
    {
        using (SqlDataAdapter sda = new SqlDataAdapter())
        {
            cmd.Connection = con;
            sda.SelectCommand = cmd;
            using (DataTable dt = new DataTable())
            {
                sda.Fill(dt);
                return dt;
            }
        }
    }
}

VB.Net

Public Sub New()
    InitializeComponent()
    dgCountries.DataSource = GetData("SELECT CountryId,CountryName FROM Countries")
End Sub

Private Sub dgCountries_CellClick(ByVal sender As Object, ByVal e As DataGridViewCellEventArgs)
    If e.RowIndex > -1 Then
        Dim countryId As Integer = Convert.ToInt32(dgCountries.CurrentRow.Cells(0).Value)
        dgStates.DataSource = GetData("SELECT StateId,StateName FROM States WHERE CountryId = " & countryId)
    End If
End Sub

Private Sub dgStates_CellClick(ByVal sender As Object, ByVal e As DataGridViewCellEventArgs)
    If e.RowIndex > -1 Then
        Dim stateId As Integer = Convert.ToInt32(dgStates.CurrentRow.Cells(0).Value)
        dgCities.DataSource = GetData("SELECT CityId,CityName FROM Cities WHERE StateId = " & stateId)
    End If
End Sub

Private Function GetData(ByVal query As String) As DataTable
    Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Dim cmd As SqlCommand = New SqlCommand(query)
    Using con As SqlConnection = New SqlConnection(conString)
        Using sda As SqlDataAdapter = New SqlDataAdapter()
            cmd.Connection = con
            sda.SelectCommand = cmd
            Using dt As DataTable = New DataTable()
                sda.Fill(dt)
                Return dt
            End Using
        End Using
    End Using
End Function

Screenshot