Problem Accessing Database Via .asmx Webservice

I just added a .asmx webservice to my project.

When i try to retrieve some information of the database using the webservice, despite using the same code as in a code behind .aspx file, it doesn't work.SqlConnection conn =

new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString);DataTable dt = new DataTable();

conn.Open();

String sql = "SELECT * FROM aspnet_Users";

//But i would suggest you to use parameterize queries or SP for security reasonsSqlCommand cmd = new SqlCommand(sql, conn);cmd.CommandType = CommandType.Text;

cmd.ExecuteNonQuery();SqlDataAdapter ad = new SqlDataAdapter(cmd);

ad.Fill(dt);

conn.Close();

 

Using this code in .aspx.cs it works, but in my .asmx it doesn't. The 'cmd.ExecuteNonQuery()'  returns '-1' in the .asmx.

I have to use the webservice because i have a Silverlight client in my application, whichs has to retrieve data from the database.

Any ideas why it works for the .aspx.cs and not for the .asmx file?