How do I stop the Invalid Length warning in Selenium from occuring?

Response.ClearContent();
string data = GetSomeData();
Response.Write(data);
Response.Flush();
Response.Close();

Response.AddHeader("Content-Length", data.Length.ToString());

Response.ClearContent();
string data = GetSomeData();
Response.AddHeader("Content-Length", data.Length.ToString());
Response.Write(data);
Response.Flush();
Response.Close();