Pattern / architecture / anonymous methods - c#-4.0

Question

I am relatively new to C#, maybe you could help me with this.
I got a couple of methods callServiceXY(param1, param2, ...) that call a certain service. For many reasons these service calls can go wrong (and I don't really care for the reason in the end). So basically I need to always wrap them with something like this - to have them execute again if something goes wrong:
var i = 3;
while(i>0)
try{
call...()
} catch{
i--;
}
i=0;
}
I'd rather write this code only once. Could I somehow have a method like tryXtimes(int x, callService()) that allows me to execute an undefined or anonymous method? (I have Javascript in mind where this is possible...)?

Answer 1

Yes this is possible. C# 3.5 added support for Action and Func<T> types. An Action won't return any value, a Func will always return a value.
You have several different versions that also accept a number of parameters. The following Console Applications describes how you could do this:
using System;
namespace Stackoverflow
{
class Service
{
public int MyMethod() { return 42; }
public void MyMethod(string param1, bool param2) { }
public int MyMethod(object paramY) { return 42; }
}
class Program
{
static void ExecuteWithRetry(Action action)
{
try
{
action();
}
catch
{
action();
}
}
static T ExecuteWithRetry<T>(Func<T> function)
{
try
{
return function();
}
catch
{
return function();
}
}
static void Main(string[] args)
{
Service s = new Service();
ExecuteWithRetry(() => s.MyMethod("a", true));
int a = ExecuteWithRetry(() => s.MyMethod(1));
int b = ExecuteWithRetry(() => s.MyMethod(true));
}
}
}
As you can see, there are two overloads for ExecuteWithRetry. One returning void, one returning a type. You can call ExecuteWithRetry by passing an Action or a Func.
--> Edit: Awesome! Just a little extra code to complete the example:
With anonymous function/method:
ExecuteWithRetry(() =>
{
logger.Debug("test");
});
And with more parameters (action, int)
Method header:
public static void ExecuteWithRetryX(Action a, int x)
Method call:
ExecuteWithRetryX(() => { logger.Debug("test"); }, 2);

Answer 2

I would use the strategy/factory pattern(s) for this. This answer https://stackoverflow.com/a/13641801/626442 gives and example of the use of the strategy/factory pattern with links. The question at the above link will give you another type of example where this pattern can be adopted.
There are great examples of these design patterns here and the following are detailed intros to the Strategy pattern and the Factory pattern. The former of the last two links also shows you how to combine the two to do something like what you require.
I hope this helps.

Answer 3

Try following
void CallServiceXY(params object []objects)
{
Console.WriteLine("a");
throw new Exception("");
}
void Retry(int maxRetryCount, Action<object[]> action, params object[] obj)
{
int retryCount = 1;
while ( retryCount <= maxRetryCount)
{
try
{
action(obj);
return;
}
catch
{
retryCount++;
}
}
}
void Main()
{
Retry(2,CallServiceXY);
Retry(2,CallServiceXY,"");
Retry(2,CallServiceXY,"","");
}
Demo here
Trick is Action<object[]> that accepts object array and return void and params keyword in Retry method.
To return non void value, Change Action<object[]> to Func<T, object[]>.