UpdateCommand

Question

what is wrong here? no error shows and nothing happens (the variables are not empty - I checked)


SqlCommand postname = new SqlCommand("UPDATE sites SET username=@username, userpass=@userpass WHERE useralias=@useralias",connection);  
connection.Open();  
SqlDataAdapter posttext = new SqlDataAdapter();  
postname.Parameters.Add("@username", SqlDbType.NVarChar, 50, username);  
postname.Parameters.Add("@userpass", SqlDbType.NVarChar, 50, userpass);  
postname.Parameters.Add("@useralias", SqlDbType.NVarChar, 50, theAlias);  
posttext.UpdateCommand = postname;


or am I not doing? I need to update the column to other values??.
I translated the interpreter, so I apologize if poorly understood.