Troubleshooting .NET 9 Application Errors Print

Common HTTP Error Codes

HTTP 500.30 - ASP.NET Core App Failed to Start

Causes:

• Application crashed during startup
• Missing dependencies
• Configuration errors

Solutions:

• Verify Application Startup File is correct in Plesk
• Check all files were uploaded
• Validate appsettings.json syntax
• Check database connection strings
• Review stdout logs in Plesk

HTTP 500.31 - Failed to Load Runtime

Cause: .NET runtime not found

Solutions:

• Verify app targets .NET 9.0
• Contact support to confirm .NET 9 is installed
• Try self-contained deployment

HTTP 502.5 - Process Failure

Cause: Application process crashed

Solutions:

• Check logs for exceptions
• Verify no startup errors
• Check for missing dependencies

Enabling Detailed Errors

Enable stdout Logging:

Edit web.config:

<aspNetCore processPath="dotnet" 
            arguments=".YourApp.dll" 
            stdoutLogEnabled="true" 
            stdoutLogFile=".logsstdout" 
            hostingModel="inprocess" />

1. Create a logs folder in your app root
2. Reproduce the error
3. Check log files in the logs folder
4. Disable logging after troubleshooting!

View Error Details (Development Only):

Temporarily in Program.cs:

if (app.Environment.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
}

Common Issues

Application Shows Old Version After Update

• Restart application in Plesk .NET Core settings
• Clear browser cache
• Verify new files were uploaded

Static Files Not Loading

• Check Document Root is correct
• Verify app.UseStaticFiles() is in Program.cs
• Ensure wwwroot folder was uploaded

Database Connection Fails

• Use localhost as server (not your domain)
• Verify credentials in Plesk Databases
• Add TrustServerCertificate=True; to connection string

App Starts Then Crashes

• Check for exceptions in startup code
• Verify all configuration is valid
• Check external service connections

Slow Application Startup

• Review database connection on startup
• Check for blocking calls in Program.cs
• Consider lazy loading for heavy services

Self-Contained Deployment Issues

App Wont Start with SCD:

• Verify correct runtime identifier (win-x64)
• Check all runtime files were uploaded
• Ensure executable permissions (contact support if needed)

Checking Application Health

Add health checks to your app:

// Program.cs
builder.Services.AddHealthChecks();

// Middleware
app.MapHealthChecks("/health");

Then visit yourdomain.com/health

Getting Support

When contacting support, provide:

• Domain name
• Exact error message
• stdout log contents
• Steps to reproduce
• .NET version (9.0)