want to delete row from gridview

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ASP.NET

i'm trying to delete row from gridview but there is an execption coming and cant understand what is the problem.

if (e.CommandName.Equals("Delete"))
{
    int index = Convert.ToInt32(e.CommandArgument);
    var id = ((Label)GridView1.Rows[index].Cells[0].FindControl("lblid")).Text.Trim(); // execption on this line

    SqlConnection con = new SqlConnection(connstring);
    string qry = "Delete from ['ISB VAS Nodes$'] where ID = " + id + "";
    SqlCommand com = new SqlCommand(qry, con);

    // open connection
    con.Open();
    int numberDeleted = com.ExecuteNonQuery();

    if (numberDeleted > 0)
    {
        Label2.Text = "Deleted";
        binddata();
    }
    else
    {
        Label2.Text = "Not Deleted";
    }

    // close connection
    con.Close();
}