Continue try block after catch. Log all exceptions in one try catch

Question

I want to do 4 actions and each one can throw an exception. I need to execute them all and log all errors that happened along the way

I can do it in a big and clumsy way :

var exceptions = new List<ExceptionType1>();
try {
    result1 = await action1();
} catch (ExceptionType1 ex1) {
    exceptions.Add(ex1);
    logger.Log(ex1);
}

try {
    result2 = await action2();
} catch (ExceptionType1 ex1) {
    exceptions.Add(ex1);
    logger.Log(ex1);
}

try {
    result3 = await action3(result1);
} catch (ExceptionType2 ex2) {
    var ex1 = new ExceptionType1(ex2);
    exceptions.Add(ex1);
    logger.Log(ex1);
}

try {
    result4 = await action4(result2);
} catch (ExceptionType2 ex2) {    
    var ex1 = new ExceptionType1(ex2);
    exceptions.Add(ex1);    
    logger.Log(ex1);
}

if (exceptions.Count > 0) {
    return false;
}

Obviously sometimes things like that bloat in size quickly I would like to do it in more elegant way :

var exceptions = new List<ExceptionType1>();
try {
    result1 = await action1();
    result2 = await action2();
    result3 = await action3(result1);
    result4 = await action4(result2);
} catch(Exception ex) {
    var ex1 = new ExceptionType1(ex);
    exceptions.Add(ex1);
    logger.Log(ex1);
    ???
    ~~Goto try block and continue executing~~
    ???

}

if (exceptions.Count > 0) {
    return false;
}

I tried to find info how to get back into try block and continue executing but was unsuccessfull. Is it possible. Is there any other way around the problem that I didn't consider?

Why do you have variables like `result1`, `result2`, `result3` in the first place. They seem like they could be put into an array/list, and then you can use a loop. — Sweeper, Sep 06 '20 at 06:32
@Sweeper I get data from various sources and want to assemble them in one object. I see no way how I can use a loop here. — Real Ambush, Sep 06 '20 at 06:34
Kind of. In reality I use result of action1 for action3. And result of action2 for action4. Actions 1,2 and 3,4 are the same type. I thought such details are not neccesary for the topic. — Real Ambush, Sep 06 '20 at 06:37
Not sure if this question could help you: https://stackoverflow.com/questions/4217643/task-waitall-and-exceptions — Steve, Sep 06 '20 at 06:42
@CaiusJard no. 3 need to be after 1, and 4 after 2. No other order dependencies — Real Ambush, Sep 06 '20 at 06:51
Yes, I guess they can be chained, if I understand what you mean by "chaining": action4(action2); action3(action1) though problem that actions 1 and 2 are HTTP requests — Real Ambush, Sep 06 '20 at 06:54

score 2 · Accepted Answer · answered Sep 06 '20 at 06:45

One way I guess (given your reequipments) is to create a local method

var exceptions = new List<Exception>();

async Task<T> DoAsync<T>(Func<Task<T>> func)
{
   try
   {
      return await func();
   }
   catch (Exception ex)
   {
      exceptions.Add(ex);
      logger.Log(ex);
   }

   return default;
}

result1 = await DoAsync(action1);
result2 = await DoAsync(action2);

if (exceptions.Count > 0)
{
   return false;
}

Sweeper · Answer 2 · 2020-09-06T06:57:35.557

Maybe you can extract this into a local function:

// declare this inside the method that contains the code you showed
async void GetResult<TResult, TException>(out TResult result, Func<Task<TResul>> resultGetter, Func<TException, ExceptionType1> mapper)
    where TException: Exception {
    try {
        result = await resultGetter();
    } catch (TException ex) {
        var ex1 = mapper(ex)
        exceptions.Add(ex1);
        logger.Log(ex1);
    }
}

Callers:

GetResult(out result1, action1, (ExceptionType1 e) => e);
GetResult(out result2, action2, (ExceptionType1 e) => e);
GetResult(out result3, async () => await action3(result1), (ExceptionType2 e) => new ExceptionType1(e));
GetResult(out result4, async () => await action4(result2), (ExceptionType2 e) => new ExceptionType1(e));

score 1 · Answer 3 · edited Sep 06 '20 at 06:58

1

how to get back into try block and continue executing.. Is it possible?

You can't do what you are looking for: https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/try-catch

The block is executed until an exception is thrown or it is completed successfully.

Once out of the block, even the variables that have been initialized are rolled back.

It's the whole point of the exception to stop the execution of the safe guarded code.

Follow the recommendations of the other two answers to simplify your code

edited Sep 06 '20 at 06:58

Caius Jard

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answered Sep 06 '20 at 06:51

Athanasios Kataras

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1

He does ask if it's possible. I don't want to bloat the answer with information already available in the other answers. – Athanasios Kataras Sep 06 '20 at 06:55

Kaeru · Answer 4 · 2020-09-06T07:52:56.367

I think WhenAll() method for Task will suit your purpose: https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/try-catch#taskwhenall-example First of all, your actions are already async. Moreover, you can divide to several WhenAll() blocks if you need to follow any order of execution

Example from docs:

public async Task action1()
{
    throw new InvalidOperationException();
}
public async Task action2()
{
    throw new NotImplementedException();
}

public async Task action3()
{
    throw new InvalidCastException();
}
public async Task DoMultipleAsync()
{
    Task theTask1 = action1();
    Task theTask2 = action2();
    Task theTask3 = action3();

    Task allTasks = Task.WhenAll(theTask1, theTask2, theTask3);

    try
    {
        await allTasks;
    }
    catch (Exception ex)
    {
        Console.WriteLine("Exception: " + ex.Message);
        Console.WriteLine("Task IsFaulted: " + allTasks.IsFaulted);
        foreach (var inEx in allTasks.Exception.InnerExceptions)
        {
            Console.WriteLine("Task Inner Exception: " + inEx.Message);
        }
    }
}

// Output:
// Exception: Operation is not valid due to the current state of the object.
// Task IsFaulted: True
// Task Inner Exception: Operation is not valid due to the current state of the object.
// Task Inner Exception: The method or operation is not implemented.
// Task Inner Exception: Specified cast is not valid.

Can you provide solution in regards to my case? This looks like the thing I would like to use. Will this work if some actions are not async? — Real Ambush, Sep 06 '20 at 07:46

Continue try block after catch. Log all exceptions in one try catch

4 Answers4

Follow the recommendations of the other two answers to simplify your code