Bind GridView with different tables from database using C# and VB.Net in ASP.Net

Hi George616,

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

HTML

<asp:DropDownList runat="server" ID="ddlTables" OnSelectedIndexChanged="OnChange" AutoPostBack="true">
    <asp:ListItem Text="Select" />
    <asp:ListItem Text="Customers" Value="Customers" />
    <asp:ListItem Text="Employees" Value="Employees" />
</asp:DropDownList>
<asp:GridView runat="server" ID="gvDetails"></asp:GridView>

Namespaces

C#

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

VB.Net

Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient

Code

C#

protected void OnChange(object sender, EventArgs e)
{
    if (ddlTables.SelectedIndex > 0)
    {
        string query = "";
        if (ddlTables.SelectedValue == "Customers")
        {
            query = "SELECT TOP 5 CustomerID Id,ContactName Name,City,Country FROM Customers";
        }

        if (ddlTables.SelectedValue == "Employees")
        {
            query = "SELECT TOP 5 EmployeeID Id,FirstName + ' ' + LastName Name,City,Country FROM Employees";
        }

        DataTable dt = GetData(query);
        gvDetails.DataSource = dt;
        gvDetails.DataBind();
    }
}

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

Protected Sub OnChange(ByVal sender As Object, ByVal e As EventArgs)
    If ddlTables.SelectedIndex > 0 Then
        Dim query As String = ""

        If ddlTables.SelectedValue = "Customers" Then
            query = "SELECT TOP 5 CustomerID Id,ContactName Name,City,Country FROM Customers"
        End If

        If ddlTables.SelectedValue = "Employees" Then
            query = "SELECT TOP 5 EmployeeID Id,FirstName + ' ' + LastName Name,City,Country FROM Employees"
        End If

        Dim dt As DataTable = GetData(query)
        gvDetails.DataSource = dt
        gvDetails.DataBind()
    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