Troubleshooting .NET Core

Common Issues and Solutions

This section provides solutions for frequently encountered problems when developing and deploying .NET Core applications. We'll cover a range of scenarios, from build errors to runtime exceptions.

Diagnostics & Logging

Effective diagnostics are crucial for pinpointing the root cause of issues. .NET Core offers several powerful tools for this purpose.

Event Logs

Applications running on Windows can log to the Windows Event Log. Ensure your application's logging framework is configured to target this output.

// Example configuration for Event Log in appsettings.json
{
  "Logging": {
    "EventLog": {
      "LogLevel": {
        "Default": "Information",
        "Microsoft": "Warning",
        "Microsoft.Hosting.Lifetime": "Information"
      },
      "SourceName": "MyDotNetCoreApp"
    }
  }
}
                

dotnet-trace Tool

The dotnet-trace tool collects runtime traces from a running .NET Core process. This is invaluable for performance analysis and identifying deadlocks.

To install:

dotnet tool install --global dotnet-trace

To collect a trace:

dotnet trace collect --process-id  -o trace.nettrace

dotnet-dump Tool

The dotnet-dump tool allows you to collect memory dumps of a running .NET Core process for post-mortem analysis using tools like WinDbg or Visual Studio.

To install:

dotnet tool install --global dotnet-dump

To collect a dump:

dotnet dump collect --process-id  -o dump.dmp

Logging Configuration

Configure your application's logging provider and level in appsettings.json. This allows you to control the verbosity of logs.

{
  "Logging": {
    "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
    }
  }
}
                

Runtime Errors

Runtime errors can manifest in various ways, from unhandled exceptions to unexpected behavior.

Exception Handling

Implement robust exception handling using try-catch blocks and consider global exception handlers for web applications.

try
{
    // Code that might throw an exception
    var result = SomeOperation();
}
catch (ArgumentNullException ex)
{
    // Handle specific exception
    LogError("Invalid argument provided.", ex);
}
catch (Exception ex)
{
    // Handle general exceptions
    LogError("An unexpected error occurred.", ex);
}
                

Out of Memory Errors (OOM)

OOM errors often indicate memory leaks or inefficient memory usage. Use profiling tools (like Visual Studio's Performance Profiler) and dotnet-dump to investigate.

Dependency Issues

Ensure all project dependencies are correctly referenced and compatible. Use dotnet list package to check installed packages and their versions.

dotnet list package

Configuration Problems

Incorrect configuration settings can lead to application startup failures or unexpected behavior. Verify:

• Connection strings
• Environment variables
• appsettings.json and appsettings.Development.json files
• Key Vault or other configuration providers

Performance Bottlenecks

Slow performance can be caused by inefficient algorithms, excessive I/O operations, or resource contention. Use tracing and profiling to identify slow code paths.

Deployment Failures

Common deployment issues include:

• Missing runtime components.
• Incorrect file permissions.
• Environment-specific configuration mismatches.
• Firewall or network issues.

Always test your deployment process thoroughly in an environment that mirrors production.

Platform-Specific Issues

.NET Core is cross-platform, but certain issues might be specific to the operating system or architecture you're running on. Consult platform-specific documentation for details.