InvalidDataContractException is an invalid collection type since it have DataContractAttribute

I have this code: ``` [DataContract] class MyData { private Int32 dato1; [DataMember] public Int32 Dato1 { get { return dato1; } set { dato1 = value; } } public MyData(Int32 dato1) { this.dato1 = dato1; } public MyData() { this.dato1 = 0; } } [DataContract] class MyCollection2 : List<MyData> { public MyCollection2() { } } ``` Then I try to serialize one object of MyCollection2 with: ``` MyCollection2 collec2 = new MyCollection2(); collec2.Add(new MyData(10)); DataContractSerializer ds = new DataContractSerializer(typeof(MyCollection2)); using (Stream s = File.Create(dialog.FileName)) { ds.WriteObject(s, collec2); } ``` Then I get the next exception: InvalidDataContractException is an invalid collection type since it have DataContractAttribute However, if I use the next class (doesn't inherit directly from List, instead has a List member): ``` [DataContract] class MyCollection1 { [DataMember] public List<MyData> items; public MyCollection1() { items = new List<MyData>(); } } ``` Here Serialization works ok. Do you know why ?. Thanks very much.