Delete Button Problem

Can someone please help with my problem.  I have a button that should delete a record using a SP, the SP works fine but I’m getting this error message when I load the page“CS0118: 'System.Web.HttpRequest.QueryString' is a 'property' but is used like a 'method'â€?  - “ptimesheetid.Value = Request.QueryString("timesheetid");â€? 
Please find the code for my button below, any help will be greatly appreciated.

 protected void DelTS(object sender, EventArgs e)
{
System.Data.SqlClient.SqlConnection objConn = new System.Data.SqlClient.SqlConnection();
objConn.ConnectionString = "Data Source=SQL03;Password=rdbx1;User ID=rdbx1;Initial Catalog=pronet_ts";
objConn.Open();
System.Data.SqlClient.SqlCommand objCmd = new System.Data.SqlClient.SqlCommand("delete_timesheets", objConn);
objCmd.CommandType = System.Data.CommandType.StoredProcedure;
System.Data.SqlClient.SqlParameter ptimesheetid = objCmd.Parameters.Add("@timesheetid", System.Data.SqlDbType.Int);

ptimesheetid.Value = Request.QueryString("timesheetid");

objCmd.ExecuteNonQuery();

objConn.Close();



}