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When debugging WCF you can see this exception. Some people advice to just disable stop on exception But it's useful feature.

The better is to go into details of this dialog and disable just this specific exception. The only small problem is that it's not in the list. But it's really a small problem. You can add it.

Just press "Add..." button, choose "Common Language Runtime Exceptions" from the drop down list and type the exception type, which is System.Configuration.ConfigurationErrorsException. Now you can disable stopping on just this exception and not all of them.

Getting output parameters when executing reader in ADO.NET

Interestingly, the values of output parameters are not available after ExcecuteReader() is called, even after all records were fetched.

To get these values it is required to either close reader (call reader.Close()) or at least call NextResult() method.

WCF - nullable values are not working in generics

Today I spent couple of hours figuring out why I suddenly got an error "Referenced type 'x`1, ... with data contract name 'xIF_Ph6aZR' in namespace 'x cannot be used since it does not match imported DataContract. Need to exclude this type from referenced types."

It was working and what I did just little bit of re-factoring. What I found is that there is a combination of conditions that does not work, while every one of them works separately:

1. Generic class is used as DataContract.
2. This class has nullable DataMember property
3. You want to reference your class in your client instead of creating in through wsdl.
   

[DataContract]
public class DummnyContract<T> where T: IBusinessObject
{

[DataMember]
public DateTime? LastModified{get;set;}

}

and then you use it like this:

[ServiceContract]
public interface IService
{
[OperationContract]
DummyContract<int> Get(int id);

}

This just does not work when you reference your assembly with declaration of this class. You can have it without class being generic. Or, you can have generic without nullable property. But not together.