CODEWITHSUNDEEP
c#unity-containerenterprise-library
Domi.Zhang
Domi.Zhang

Reputation: 1705

How to swallow Exception by IInterceptionBehavior?

I have a IInterceptionBehavior like blow:

public class TraceBehavior : IInterceptionBehavior
{
    public IEnumerable<Type> GetRequiredInterfaces()
    {
        return Type.EmptyTypes;
    }

    public IMethodReturn Invoke(IMethodInvocation input, GetNextInterceptionBehaviorDelegate getNext)
    {
        Console.WriteLine(string.Format("Invoke method:{0}",input.MethodBase.ToString()));
        IMethodReturn result = getNext()(input, getNext);
        if (result.Exception == null)
        {
            Console.WriteLine("Invoke successful!");
        }
        else 
        {
            Console.WriteLine(string.Format("Invoke faild, error: {0}", result.Exception.Message));
            result.Exception = null;
        }
        return result;
    }

    public bool WillExecute { get { return true; } }
}

Regardless of whether I put it upon methods or not, exception throw always. Anyone can help me?

Upvotes: 4

Views: 1344

Answers (1)

Randy Levy
Randy Levy

Reputation: 22655

The code looks OK but you haven't shown how the interception is registered and how the object is being called.

Assuming that interception is being called then if I were to guess it would be that that the method invoked returns a value type and IMethodReturn.ReturnValue is null which is causing a NullReferenceException.

If that is the case then perhaps returning the default value for a value type would solve your issue:

public IMethodReturn Invoke(IMethodInvocation input, GetNextInterceptionBehaviorDelegate getNext)
{
    Console.WriteLine(string.Format("Invoke method:{0}", input.MethodBase.ToString()));
    IMethodReturn result = getNext()(input, getNext);
    if (result.Exception == null)
    {
        Console.WriteLine("Invoke successful!");
    }
    else
    {
        Console.WriteLine(string.Format("Invoke faild, error: {0}", result.Exception.Message));
        result.Exception = null;

        Type type = ((MethodInfo)input.MethodBase).ReturnType;

        if (type.IsValueType)
        {
            result.ReturnValue = Activator.CreateInstance(type);
        }
    }
    return result;
}

Upvotes: 4

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