[C#] errore select strano..

[drummino^]

ciao ragazzi,
ho questo codice ma mi restituisce un errore strano...

       
        private void ResizeAndSave(Stream imgStr,int Width, int Height,string FileName)
        {
            MySqlConnection connection = new MySqlConnection();
            connection.ConnectionString = "Data Source=localhost; Database=sup; User ID=admin; password=rda";
            //connection.Open();
            
            System.Data.SqlClient.SqlCommand cmd = new SqlCommand("SELECT id_foto from fotografie order by id_foto DESC", connection);
            try
            {
            connection.open;
            SqlDataReader myReader = cmd.ExecuteReader();
            int id = Myreader("id_foto");
            }
            catch(Exception e)
                {
            Console.WriteLine("Exception Occured -->> {0}",e);
            } 

il messaggio d'errore è questo:

escription: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: CS0246: The type or namespace name 'SqlCommand' could not be found (are you missing a using directive or an assembly reference?)

Source Error:

Line 15: //connection.Open();
Line 16:
Line 17: System.Data.SqlClient.SqlCommand cmd = new SqlCommand("SELECT id_foto from fotografie order by id_foto DESC", connection);
Line 18: try
Line 19: {

qualche idea !?