Question

A WCF service exposing multiple elements in DataContract as DataMember

[DataMember(IsRequired = true, EmitDefaultValue = false)] public string Source;  [DataMember(IsRequired = true, EmitDefaultValue = false)] public string Target; 

In generated proxy (through add service reference in VS 2008) at client, the client can pass null or empty string in Source or Target. how can I enforce Source and Target as Required at client side. i.e. client should get an exception if Source or Target is set to null, before invoking the service call.

Answer 1

Well, both null (xsi:nil) and an empty string are values – they just aren’t values you want.

During deserialization (at client or server):

You could try putting some code in the setter to throw an exception for invalid values?

Alternatively (for more complex cases), I believe that data-contracts support deserialization callbacks, which should allow you to validate…

For example, you can add (in a partial class, if necessary, at the client):

[OnDeserialized] internal void OnDeserialized(StreamingContext context) {     if (string.IsNullOrEmpty(Bar))     {         throw new InvalidOperationException('No Bar!');     } } 

For pre-send checks (at the client), you would have to add an extra validation method, or perhaps (again, in a partial class):

[OnSerializing] internal void OnSerializing(StreamingContext context) {     if (string.IsNullOrEmpty(Bar))     {         throw new InvalidOperationException('No Bar!');     } } 

However, the server must also validate this – you can’t assume that it is your client code that has sent the message.