Question

Currently I do something like this:

class Foo {
    // Declare Fields
    [FieldName("F_BAR")] public int?    Bar;
    [FieldName("F_BAZ")] public int?    Baz;
    [FieldName("BLARG")] public double? Bee;
    
    // And a custom selector
    public static string FooFields() {
        // which looks something like:
        StringBuilder fields = new StringBuilder();
        foreach( FieldInfo f in typeof(Foo).GetFields() )
            fields.Append(", " +
                f.GetCustomAttributes(
                    typeof(FieldNameAttribute),
                    false)[0].FieldName );
        return fields.ToString().Substring(2);
    }
    // .. which will be used like this:
    public static string ExampleSelect() {
        return "select " + Foo.FooFields() + " from tablename";
    }
    
    // And a custom reader, formatted for the custom selector
    public static Foo Read(DbDataReader reader) {
        int i = -1;
        return new Foo {
            Bar = reader.IsDBNull(++i)
                ? (int?)null
                : Convert.ToInt32(reader.GetValue(i)),
            Baz = reader.IsDBNull(++i)
                ? (int?)null
                : Convert.ToInt32(reader.GetValue(i)),
            Bee = reader.IsDBNull(++i)
                ? (double?)null
                : Convert.ToDouble(reader.GetValue(i))
        };
    }
}

Currently, it works. I realized today, that this depends on the fields being returned from GetFields() in the order that I declared them in the class. Is this always the expected behavior? Only in .NET?

EDIT: If there are cases when it doesn’t work, can I assume it will work as long as I don’t do anything to upset the cache?

Answer 1

No the GetFields method does not return the FieldInfo values in any particular order. Here is the relevant documentation snippet from MSDN

The GetFields method does not return fields in a particular order, such as alphabetical or declaration order. Your code must not depend on the order in which fields are returned, because that order varies.