Pass DropDownList value in QueryString to another page and populate GridView in ASP.Net using C# and VB.Net

Hi ukd,

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

For this sample I have used NorthWind database that you can download using the link given below.

Download Northwind Database

Namespaces

C#

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

VB.Net

Imports System.Data.SqlClient
Imports System.Data

HTML

First.aspx

<asp:DropDownList runat="server" ID="ddlCountries">
    <asp:ListItem Text="USA" Value="USA" />
    <asp:ListItem Text="UK" Value="UK" />
    <asp:ListItem Text="Canada" Value="Canada" />
</asp:DropDownList>
<asp:Button ID="btnTransfer" Text="Transfer" OnClick="Transfer" runat="server" />

Extract.aspx

<asp:GridView runat="server" ID="gvCustomers" AutoGenerateColumns="false">
    <Columns>
        <asp:BoundField DataField="CustomerID" HeaderText="CustomerID" />
        <asp:BoundField DataField="ContactName" HeaderText="ContactName" />
        <asp:BoundField DataField="City" HeaderText="City" />
        <asp:BoundField DataField="Country" HeaderText="Country" />
    </Columns>
</asp:GridView>

C#

First.aspx.cs

protected void Transfer(object sender, EventArgs e)
{
    Server.Transfer("Extract.aspx?Country=" + ddlCountries.SelectedValue);
}

Extract.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{
    if (!string.IsNullOrEmpty(Request.QueryString["Country"]))
    {
        string country = Request.QueryString["Country"];
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT CustomerID,ContactName,City,Country FROM Customers WHERE Country = @Country", con))
            {
                cmd.Parameters.AddWithValue("@Country", country);
                using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                {
                    DataTable dt = new DataTable();
                    da.Fill(dt);
                    gvCustomers.DataSource = dt;
                    gvCustomers.DataBind();
                }
            }
        }
    }
}

VB.Net

First.aspx.vb

Protected Sub Transfer(ByVal sender As Object, ByVal e As EventArgs)
    Server.Transfer("Extract.aspx?Country=" & ddlCountries.SelectedValue)
End Sub

Extract.aspx.vb

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not String.IsNullOrEmpty(Request.QueryString("Country")) Then
        Dim country As String = Request.QueryString("Country")
        Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
        Using con As SqlConnection = New SqlConnection(constr)
            Using cmd As SqlCommand = New SqlCommand("SELECT CustomerID,ContactName,City,Country FROM Customers WHERE Country = @Country", con)
                cmd.Parameters.AddWithValue("@Country", country)
                Using da As SqlDataAdapter = New SqlDataAdapter(cmd)
                    Dim dt As DataTable = New DataTable()
                    da.Fill(dt)
                    gvCustomers.DataSource = dt
                    gvCustomers.DataBind()
                End Using
            End Using
        End Using
    End If
End Sub

Screenshot