GridView RowCommand Error: Index was out of range. Must be non-negative and less than the size of the collection

Hi kelsen1989,

Check this sample.

Database

For this example I have used of Northwind database that you can download using the link given below.

Download Northwind Database

HTML

<asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false" AllowPaging="true"
    OnPageIndexChanging="gvCustomers_PageIndexChanging" OnRowCommand="OnRowCommand"
    DataSourceID="SqlDataSource1">
    <Columns>
        <asp:TemplateField ShowHeader="False">
            <ItemTemplate>
                <asp:Button ID="btnSelect" CommandArgument='<%# Container.DataItemIndex %>' CommandName="Select"
                    runat="server" Text="Select Report" />
                <asp:Button ID="btnReport" Text="Get Report" runat="server" OnClick="GetReport" />
            </ItemTemplate>
            <ItemStyle Width="80px" />
        </asp:TemplateField>
        <asp:BoundField DataField="CustomerID" HeaderText="CustomerID" />
        <asp:BoundField DataField="ContactName" HeaderText="Name" />
        <asp:BoundField DataField="City" HeaderText="City" />
        <asp:BoundField DataField="Country" HeaderText="Country" />
        <asp:TemplateField>
            <ItemTemplate>
                <asp:DropDownList ID="ddlCountry" runat="server" AppendDataBoundItems="true" DataTextField="Country"
                    DataValueField="Country" DataSourceID="SqlDataSource2">
                </asp:DropDownList>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:constr %>"
    SelectCommand="SELECT [CustomerID], [ContactName], [City], [Country] FROM [Customers]">
</asp:SqlDataSource>
<asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:constr %>"
    SelectCommand="SELECT DISTINCT [Country] FROM [Customers] WHERE [Country] !=''">
</asp:SqlDataSource>

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 GetReport(object sender, EventArgs e)
{
    GridViewRow row = ((sender as Button).NamingContainer as GridViewRow);
    int index = ((sender as Button).NamingContainer as GridViewRow).RowIndex;
    gvCustomers.AllowPaging = false;
    gvCustomers.DataBind();

    DropDownList ddlcountry = (row.FindControl("ddlCountry") as DropDownList);
    string country = ddlcountry.SelectedValue;
    Response.Redirect("Report.aspx?country=" + country);
}

protected void gvCustomers_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
    this.gvCustomers.PageIndex = e.NewPageIndex;
}

private void BindCustomers()
{
    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["constr"].ConnectionString))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT CustomerID,ContactName,City,Country FROM Customers", con))
        {
            cmd.CommandType = CommandType.Text;
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                sda.SelectCommand = cmd;
                DataTable dt = new DataTable();
                sda.Fill(dt);
                this.gvCustomers.DataSource = dt;
                this.gvCustomers.DataBind();
            }
        }
    }
}

VB.Net

Protected Sub GetReport(ByVal sender As Object, ByVal e As EventArgs)
    Dim row As GridViewRow = (TryCast((TryCast(sender, Button)).NamingContainer, GridViewRow))
    Dim index As Integer = (TryCast((TryCast(sender, Button)).NamingContainer, GridViewRow)).RowIndex
    gvCustomers.AllowPaging = False
    gvCustomers.DataBind()
    Dim ddlcountry As DropDownList = (TryCast(row.FindControl("ddlCountry"), DropDownList))
    Dim country As String = ddlcountry.SelectedValue
    Response.Redirect("Report.aspx?country=" & country)
End Sub

Protected Sub gvCustomers_PageIndexChanging(ByVal sender As Object, ByVal e As GridViewPageEventArgs)
    Me.gvCustomers.PageIndex = e.NewPageIndex
End Sub

Private Sub BindCustomers()
    Using con As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("constr").ConnectionString)
        Using cmd As SqlCommand = New SqlCommand("SELECT CustomerID,ContactName,City,Country FROM Customers", con)
            cmd.CommandType = CommandType.Text
            Using sda As SqlDataAdapter = New SqlDataAdapter()
                sda.SelectCommand = cmd
                Dim dt As DataTable = New DataTable()
                sda.Fill(dt)
                Me.gvCustomers.DataSource = dt
                Me.gvCustomers.DataBind()
            End Using
        End Using
    End Using
End Sub

Screenshot