What causes "[{nameof(Logger)}] cannot be null in {GetType().Name}" in stride3d/stride?

Assign a LoggerResult instance to the Logger property, e.g. new LoggerResult() or a suitable logger from your host application.

stride3d/stride · error · InvalidOperationException

[ ] cannot be null in

Error message

[{nameof(Logger)}] cannot be null in {GetType().Name}

What it means

TemplateGeneratorParameters.ValidateParameters throws this InvalidOperationException when the Logger property (a LoggerResult that collects generation diagnostics) is null. Stride's template generators report progress and errors through this logger, so validation requires one before running; it is the last mandatory field checked in the base ValidateParameters.

Solutions

Assign a LoggerResult instance to the Logger property, e.g. new LoggerResult() or a suitable logger from your host application.
In tests or headless tools, use a console or in-memory ILogger implementation deriving from LoggerResult to capture messages.
If copying parameters manually, mirror the copy constructor and include Logger = parameters.Logger.

Example fix

// before
var p = new SessionTemplateGeneratorParameters { Name = "MyGame", OutputDirectory = dir, Description = desc, Session = session };
p.Validate(); // throws: Logger null

// after
var logger = new LoggerResult();
var p = new SessionTemplateGeneratorParameters { Name = "MyGame", OutputDirectory = dir, Description = desc, Logger = logger, Session = session };
p.Validate();

Defensive patterns

Strategy: validation

Validate before calling

if (p.Logger == null)
    throw new ArgumentException("TemplateGeneratorParameters.Logger must be set to a LoggerResult before Validate().");

Type guard

bool HasLogger(TemplateGeneratorParameters p) => p.Logger is not null;

Try / catch

try { p.Validate(); }
catch (InvalidOperationException ex) when (ex.Message.Contains(nameof(TemplateGeneratorParameters.Logger)))
{
    // create a default LoggerResult and retry
}

Prevention

Always create a LoggerResult (console or in-memory) in tests and headless tools before generation.
Copy parameters with the provided copy constructor, which carries Logger over automatically.
Wire a single shared logger into all template generation calls in your application.

When it happens

Trigger: Calling Validate() on any TemplateGeneratorParameters-derived object with all other fields set but Logger never assigned — common in tests or headless tools where no editor logger is available.

Common situations: Unit tests exercising template generation without creating a logger; CLI tools skipping logger setup; refactors that dropped the Logger assignment when cloning parameters into a new parameters instance (the copy constructor does copy Logger, manual copies often don't).

Related errors

AI-assisted analysis of stride3d/stride@96fad776d2 (2026-09-14). Data as JSON: /api/errors/cb0611b8bc695dc2. Report an issue: GitHub.

Appendix: source

Thrown at sources/assets/Stride.Core.Assets/Templates/TemplateGeneratorParameters.cs:231

    }

    protected virtual void ValidateParameters()
    {
        if (Name == null)
        {
            throw new InvalidOperationException($"[{nameof(Name)}] cannot be null in {GetType().Name}");
        }
        if (OutputDirectory == null && Description.Scope == TemplateScope.Session)
        {
            throw new InvalidOperationException($"[{nameof(OutputDirectory)}] cannot be null in {GetType().Name}");
        }
        if (Description == null)
        {
            throw new InvalidOperationException($"[{nameof(Description)}] cannot be null in {GetType().Name}");
        }
        if (Logger == null)
        {
            throw new InvalidOperationException($"[{nameof(Logger)}] cannot be null in {GetType().Name}");
        }
    }
}

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