Async and Await Execution in .NetCore

In an asynchronous method, whether the second method executes if the first one throws an error depends on how the asynchronous operations are structured. Here's an explanation with examples.

Scenario 1: Sequential Execution

If the two asynchronous methods are called one after the other (sequentially), the second method will not execute if the first method throws an exception, unless you explicitly handle the exception.

Example

public async Task MyAsyncMethod()
{
    await FirstAsyncMethod(); // If this throws, the next line will not execute.
    await SecondAsyncMethod(); 
}

If FirstAsyncMethod throws an exception, SecondAsyncMethod will not be executed unless you handle the exception explicitly.

Handling the Exception

Scenario 2: Parallel Execution

public async Task MyAsyncMethod()
{
    try
    {
        await FirstAsyncMethod();
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Error: {ex.Message}");
    }

    await SecondAsyncMethod(); // Executes regardless of the first method's outcome.
}

If the two asynchronous methods are executed concurrently (in parallel), the second method will still run even if the first one throws an exception.

Example

Here, both methods start execution immediately. If FirstAsyncMethod throws an exception, it will not stop SecondAsyncMethod from running.

Scenario 3: Aggregate Exception Handling

If you want to wait for both methods to complete and handle exceptions together, you can use Task.WhenAll.

Example

public async Task MyAsyncMethod()
{
    try
    {
        await Task.WhenAll(FirstAsyncMethod(), SecondAsyncMethod());
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Error: {ex.Message}");
    }
}

If either method throws an exception, the exception will be captured, and both methods will attempt to complete.

Summary

1. Sequential Calls: The second method will not execute if the first method throws an exception unless you handle the exception explicitly.
2. Parallel Calls: Both methods run independently; one throwing an exception doesn't stop the other.
3. Combined Calls with Task.WhenAll: Both methods execute, and exceptions from either are handled after both complete.

Recommendation - Use exception handling (try-catch) as appropriate to ensure the desired execution flow.