Returning a default value in case of errors

Ever wrote something like this?

1. if (a != null && a.b != null && a.b.c != null)  
2.   result = a.b.c.d;  
3. else  
4.   result = null;  

I hate it. Given that I'm processing some XML files whose schemas I cannot change, there's not much to be done but bite the bullet.

This page gave me the idea for the following helper functions:

1. public static T Eval<T, ExceptionClass>(Func<T> func, Func<ExceptionClass, T> onError)  
2.   where ExceptionClass: Exception  
3. {  
4.   try  
5.   {  
6.     return func();  
7.   }  
8.   catch (ExceptionClass e)  
9.   {  
10.     return onError(e);  
11.   }  
12. }  
13.   
14. public static T Eval<T>(Func<T> func, Func<Exception, T> onError)  
15. {  
16.   return Eval<T, Exception>(func, onError);  
17. }  
18.   
19. public static T Eval<T>(Func<T> func, T defaultValue)  
20. {  
21.   return Eval<T, Exception>(func, e => defaultValue);  
22. }  

Now I can write this:

1. result = Helper.Eval(() => a.b.c.d, null);  

As an aside, it's really annoying not being able to write something like this:

1. public static T Something<T>(Func<T[]> func)  

instead of writing say 5 overloads for Func<T> to Func<T1, T2, T3, T4, T>.