Decorating service methods calls for centralized error processing

I have multiple services with a lot of methods. Every method returns an int as a result code. All methods have 2 types of signatures:

• Only with IN params

• n of IN params and m OUT params in the end (in most cases 1 OUT param)

Up until now I came up with this solution:

```
#region Decorators

#region [Getters]

#region [Void]
protected delegate int KeeperAPIDelegateVoid(string sessionID, T1 obj1);
protected delegate int KeeperAPIDelegateVoid(string sessionID, T1 obj1, T2 obj2);

protected void DataGrabber(KeeperAPIDelegateVoid action, params object[] args)
{
int result = action.Invoke(SessionID, (T1)args[0]);
if (result != 0) throw HandleError(result);
}
protected void DataGrabber(KeeperAPIDelegateVoid action, params object[] args)
{
int result = action.Invoke(SessionID, (T1)args[0], (T2)args[1]);
if (result != 0) throw HandleError(result);
}
#endregion

#region [Typed]
protected delegate int KeeperAPIDelegate(string sessionID, out TReturn rObj);
protected delegate int KeeperAPIDelegate(string sessionID, T1 obj1, out TReturn rObj);
protected delegate int KeeperAPIDelegate(string sessionID, T1 obj1, T2 obj2, out TReturn rObj);
protected delegate int KeeperAPIDelegate(string sessionID, T1 obj1, T2 obj2, T3 obj3, out TReturn rObj);
protected delegate int KeeperAPIDelegate(string sessionID, T1 obj1, T2 obj2, T3 obj3, T4 obj4, T5 obj5, out TReturn rObj);
protected delegate int KeeperAPIDelegate(string sessionID, T1 obj1, T2 obj2, T3 obj3, T4 obj4, T5 obj5, T6 obj6, out TReturn1 rObj1, out TReturn2 rObj2, out TReturn3 rObj3);

protected TReturn DataGrabber(KeeperAPIDelegate action)
{
TReturn data;
int result = action.Invoke(SessionID, out data);
if (result == 0) return data;
throw HandleError(result);
}
protected TReturn DataGrabber(KeeperAPIDelegate action, params object[] args)
{
TReturn data;
int result = action.Invoke(SessionID, (T1)args[0], out data);
if (result == 0) return data;
throw HandleError(resul

If the service methods are not changeable, I don't see a solution that is fundamentally better then yours...

• If there are only one or a few methods with 3 return values, consider to create more descriptive custom types for the return values (instead of using Tuple).

• The check for (result == 0) is implemented for each method. You could do that within the method HandleError. However, that requires, that HandleError does not return the exception but throws it directly if result is != 0.

StackExchange Code Review Q#138323, answer score: 2