Question

I have a Sql Utility class which contains a lot of handy methods around Sql queries.
This class contains the following method:

public static T ExecuteScalar<T>(
    string query, 
    SqlConnection connection, 
    params SqlParameter[] parameters) 
    where T : class, new()
{
    SqlCommand command =
        CreateCommand(query, connection, parameters);

    return command.ExecuteScalar() as T;
}

Is it possible to return for example Guid objects or other non-nullable classes.

Something like this:

Guid result = 
    SqlUtils.ExecuteScalar<Guid>(
        @"SELECT [Id] FROM [dbo].[MyTable]
            WHERE [Column1] = @Param1", 
        connection, 
        new SqlParameter("@Param1", "someValue"));

Answer 1

You can use default(T) (and you should remove the generic type constraints):

SqlCommand command = 
    CreateCommand(query, connection, parameters);

object value = command.ExecuteScalar();

if (value == null || value is DbNull)
{
    return default(T)'
}

return (T)value;