Exceptions

JavaScript calling .NET

If JavaScript code calls a .NET property or method that throws an exception, the exception gets re-thrown to JS as a JavaScript Error.

For now, only the base Error type is thrown. Eventually the JS marshaller could generate different Error subclasses for each .NET Exception subclass.

To explicitly throw a specific type of error from .NET to JavaScript, use the one of the Throw* methods of the JSError class.

.NET calling JavaScript

If .NET code calls a JS function that throws an error, the error gets re-thrown to .NET as a JSException. The JSException.Error property provides access to the error value that was thrown from JavaScript.

Combined stack traces

When exceptions/errors thrown in .NET or JS are propagated across the boundary between runtimes, their stack traces are automatically combined.

In this example, JavaScript code calls a .NET method that throws an exception:

Error: Test error thrown by .NET.
    at Microsoft.JavaScript.NodeApi.TestCases.Errors.ThrowDotnetError(String message) in D:\node-api-dotnet\test\TestCases\Errors.cs:line 13
    at Microsoft.JavaScript.NodeApi.Generated.Module.Errors_ThrowDotnetError(JSCallbackArgs __args) in napi-dotnet.NodeApi.g.cs:line 357
    at Microsoft.JavaScript.NodeApi.JSNativeApi.InvokeCallback[TDescriptor](napi_env env, napi_callback_info callbackInfo, JSValueScopeType scopeType, Func`2 getCallbackDescriptor) in JSNativeApi.cs:line 1070
    at catchDotnetError (D:\node-api-dotnet\test\TestCases\errors.js:14:12)
    at Object.<anonymous> (D:\node-api-dotnet\test\TestCases\errors.js:41:1)

• Frame 5: ThrowDotnetError() - C# method that threw the exception
• Frame 4: Errors_ThrowDotnetError() - Marshalling code (auto-generated)
• Frame 3: InvokeCallback() - JS to .NET transition
• Frame 2: catchDotnetError() - JS code that called the .NET method and caught its error
• Frame 0: Top-level JS statement that called catchDotnetError()