WCF callback occurs error when serialize

Question

I am programming a Azure WCF application.

A datacontract defined as below:
[DataContract]
public class UserInfo
{
[DataMember]
public string UserName { get; set; }
[DataMember]
public int UserID { get; set; }
[DataMember]
public bool IsOnline { get; set; }
}

then I define a datacontract in my WCF service:

[DataContract(Name="UserInfo")]
public class ServiceUserInfo : UserInfo
{
[IgnoreDataMember]
public ICallback Callback { get; set; }
}

Then in the service contract, it will callback to client, the method as below

private void NoticeUsers(UserInfo currentuser)
{
var users = UserManager.GetAllActiveUsers();
foreach (var user in users)
{
if (user.UserName == currentuser.UserName)
continue;
user.Callback.UpdateUserList(currentuser);
}
}

Actually I pass a ServiceUserInfo object as parameter to the NoticeUsers method. Then an error will occurs as below:

There was an error while trying to serialize parameter http://tempuri.org/:user. The InnerException message was 'Type 'WCFServiceWebRole.ServiceUserInfo' with data contract name 'UserInfo:http://schemas.datacontract.org/2004/07/WCFServiceWebRole' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.'. Please see InnerException for more details.

I am not able to find solution for this issue.Please help.

Answer 1

I think I have found the root cause of the issue, however I do not know why.

The problem is caused by the Namespace attribute of the Service contract.

I didn't set the namespace of my service contract interface and data contract interface. I thought it would be set by default and it won't cause any problem. But actually the issue of this thread is caused by the Namespace attribute. I set a Namespace attribute for both service contract and data contract, of course the same namespace, then it worked. The problem never happens again.

However, I do not know why it caused this issue. If I do not set Namespace, it will be a default value of "http://tempuri.org", isn't it?