MSDN Documentation

1. Runtime Exceptions and Errors

Understanding and diagnosing runtime exceptions is crucial for application stability. Here are common approaches:

• Analyze Stack Traces: The stack trace provides the sequence of method calls leading to the error. Identify the originating exception type and the specific line of code.
• Use Debugging Tools: Visual Studio's debugger is invaluable. Set breakpoints, inspect variables, and step through your code to pinpoint the cause.
• Logging: Implement robust logging using frameworks like Serilog, NLog, or the built-in .NET logging. Log exceptions with detailed context (e.g., user actions, input parameters).
• Common Exception Types:
  • NullReferenceException: A variable was used before it was assigned a value.
  • IndexOutOfRangeException: An array or collection index was outside its valid range.
  • FileNotFoundException: A required file could not be found.
  • InvalidOperationException: An operation was attempted on an object in an invalid state.

Example of handling an exception:

try
{
    // Code that might throw an exception
    int result = 10 / 0;
}
catch (DivideByZeroException ex)
{
    Console.Error.WriteLine($"An error occurred: {ex.Message}");
    // Log the exception details for further analysis
    // Log.Error(ex, "Division by zero attempted.");
}
finally
{
    // Cleanup code, runs regardless of whether an exception occurred
    Console.WriteLine("Execution finished.");
}

2. Performance Bottlenecks

Slow application performance can stem from various sources. Profiling and optimization techniques are key.

• Profiling: Use tools like the .NET Performance Profiler in Visual Studio, PerfView, or dotnet-trace to identify CPU-bound and memory-bound operations.
• Memory Leaks: Monitor memory usage. Tools like dotMemory or the Memory Usage tool in Visual Studio can help detect and diagnose memory leaks. Ensure objects are properly disposed of, especially those implementing IDisposable.
• Database Queries: Inefficient database queries are a common cause of slowness. Optimize SQL queries, use indexing effectively, and consider caching.
• Asynchronous Operations: Utilize asynchronous programming (async/await) to prevent blocking the UI thread or worker threads, improving responsiveness.
• Garbage Collection (GC): Understand how the GC works. High GC pressure can impact performance. Avoid excessive object allocations in performance-critical code paths.

3. Deployment and Configuration Issues

Problems can arise during the deployment or configuration of your .NET application.

• Application Configuration: Ensure configuration files (appsettings.json, web.config) are correctly deployed and accessible. Verify connection strings, API keys, and other settings.
• Runtime Versions: Make sure the target .NET runtime version is installed on the deployment server and matches the version the application was built against.
• Dependencies: All required NuGet packages and native dependencies must be present. Check for missing DLLs or incorrect versions.
• Permissions: The application pool identity (for IIS) or the user account running the service needs appropriate permissions to access files, directories, and network resources.
• Environment Variables: For cloud-native applications and modern .NET, environment variables are often used for configuration. Ensure they are set correctly in the deployment environment.

4. Network and Connectivity Problems

Issues related to network communication can be challenging to diagnose.

• Firewalls: Ensure firewalls (local or network) are not blocking necessary ports for your application or its dependencies (e.g., database connections, API endpoints).
• DNS Resolution: Verify that hostnames can be resolved correctly.
• Service Availability: Check if external services (APIs, databases) are running and accessible.
• SSL/TLS Errors: If using HTTPS, ensure certificates are valid, correctly installed, and trusted by the client.