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5.3 - Specific Debugging Scenarios

Different types of applications and issues require specialized debugging approaches. This chapter covers techniques for debugging specific scenarios that C# developers commonly encounter.

5.3.1 - Debugging Exceptions​

Exceptions are a common source of bugs in C# applications. Effective exception debugging requires understanding the exception type, message, and stack trace.

5.3.1.1 - Exception Settings​

Configure Visual Studio to break when exceptions are thrown:

  1. Open the Exception Settings window (Debug > Windows > Exception Settings)
  2. Check the exceptions you want to break on
  3. Choose whether to break when exceptions are thrown or when they're unhandled

5.3.1.2 - Analyzing Exception Information​

When an exception occurs, examine:

  1. Exception Type: Indicates the category of the problem (e.g., NullReferenceException)
  2. Exception Message: Provides details about what went wrong
  3. Stack Trace: Shows where the exception occurred and the call path
try
{
    ProcessData(null);
}
catch (Exception ex)
{
    // Examine ex.GetType().Name, ex.Message, and ex.StackTrace
    Console.WriteLine($"Exception Type: {ex.GetType().Name}");
    Console.WriteLine($"Message: {ex.Message}");
    Console.WriteLine($"Stack Trace: {ex.StackTrace}");
}

5.3.1.3 - Inner Exceptions​

Check for inner exceptions, which often contain the root cause:

catch (Exception ex)
{
    var currentEx = ex;
    while (currentEx != null)
    {
        Console.WriteLine($"Exception: {currentEx.Message}");
        currentEx = currentEx.InnerException;
    }
}

5.3.2 - Debugging Multithreaded Applications​

Multithreaded applications introduce unique debugging challenges due to race conditions, deadlocks, and non-deterministic behavior.

5.3.2.1 - Threads Window​

Use the Threads window to monitor and control threads during debugging:

  • Access: Debug > Windows > Threads
  • Features: Thread List, Thread Switching, Thread Freezing

5.3.2.2 - Parallel Stacks Window​

The Parallel Stacks window visualizes the call stacks of multiple threads:

  • Access: Debug > Windows > Parallel Stacks
  • Features: Thread Call Stacks, Task Call Stacks

5.3.2.3 - Debugging Race Conditions​

To debug race conditions:

  1. Use thread-safe logging to record thread activities
  2. Set conditional breakpoints based on thread ID
  3. Use the Parallel Tasks window to monitor task execution
// Thread-safe logging
private static readonly object _lockObject = new object();

public void LogThreadActivity(string message)
{
    lock (_lockObject)
    {
        Console.WriteLine($"Thread {Thread.CurrentThread.ManagedThreadId}: {message}");
    }
}

5.3.3 - Debugging Async Code​

Asynchronous code introduces additional complexity to debugging due to the non-linear execution flow.

5.3.3.1 - Async Call Stack​

Visual Studio maintains the logical call stack across async boundaries:

public async Task ProcessOrderAsync(Order order)
{
    await ValidateOrderAsync(order);
    await CalculateTotalAsync(order);
    await SaveOrderAsync(order);
}

When debugging, the call stack will show the logical flow, not just the current thread's stack.

5.3.3.2 - Task Status​

Examine Task status to understand the state of asynchronous operations:

var task = ProcessOrderAsync(order);
// Check task.Status in the Watch window
// Possible values: Created, WaitingForActivation, WaitingToRun, Running, 
// WaitingForChildrenToComplete, RanToCompletion, Canceled, Faulted

5.3.3.3 - Async Debugging Tools​

Use specialized tools for async debugging:

  1. Tasks Window: Shows all active tasks (Debug > Windows > Tasks)
  2. Parallel Tasks: Visualizes task relationships and states
  3. Async Debugging in Immediate Window: Evaluate async expressions with .Result

5.3.4 - Remote Debugging​

Remote debugging allows you to debug applications running on different machines.

5.3.4.1 - Setting Up Remote Debugging​

To set up remote debugging:

  1. Install the Remote Debugging Tools on the target machine
  2. Configure firewall settings to allow communication
  3. Start the Remote Debugging Monitor on the target machine
  4. Connect from Visual Studio using the "Attach to Process" dialog

5.3.4.2 - Debugging Web Applications​

For web applications, you can:

  1. Use "Attach to Process" to connect to IIS or IIS Express
  2. Configure Visual Studio to use a remote web server
  3. Use browser developer tools in conjunction with Visual Studio

5.3.4.3 - Debugging in Production-Like Environments​

Remote debugging allows you to debug in environments that more closely match production:

// Add diagnostic code that only runs in specific environments
#if DEBUG
    Logger.LogDebug($"Processing order {order.Id} with {order.Items.Count} items");
#endif

5.3.5 - Debugging Production Issues​

Production debugging requires different approaches due to limited access and the need to minimize impact.

5.3.5.1 - Logging and Telemetry​

Implement comprehensive logging to capture information about production issues:

try
{
    ProcessOrder(order);
}
catch (Exception ex)
{
    _logger.LogError(ex, "Error processing order {OrderId}", order.Id);
    throw;
}

5.3.5.2 - Crash Dumps​

Collect and analyze crash dumps to diagnose production issues:

  1. Configure Windows Error Reporting to collect dumps
  2. Use tools like WinDbg or Visual Studio to analyze dumps
  3. Look for exception information and call stacks

5.3.5.3 - Feature Flags​

Use feature flags to control the behavior of your application in production:

if (_featureManager.IsEnabled("DetailedLogging"))
{
    _logger.LogDebug("Detailed order information: {@Order}", order);
}

In the next chapter, we'll explore advanced debugging techniques, including logging frameworks and structured logging, to further enhance your debugging capabilities.