NET 6 REST API Service as a Lambda: error during the query

Question

I have created the NET 6 service using AWS SDK Template. It works fine in Windows. I have deployed it to AWS Lambda. It starts ok, It should show Swagger UI but I see logs with an unknown error:

2023-03-01T16:31:11.189+01:00	INIT_START Runtime Version: dotnet:6.v13 Runtime Version ARN: arn:aws:lambda:eu-central-1::runtime:699f346a05dae24c58c45790bc4089f252bf17dae3997e79b17d939a288aa1ec

2023-03-01T16:31:12.074+01:00	2023-03-01T15:31:12.063Z [Information] Microsoft.Hosting.Lifetime: Application started. Press Ctrl+C to shut down.

2023-03-01T16:31:12.076+01:00	2023-03-01T15:31:12.075Z [Information] Microsoft.Hosting.Lifetime: Hosting environment: Production

2023-03-01T16:31:12.076+01:00	2023-03-01T15:31:12.076Z [Information] Microsoft.Hosting.Lifetime: Content root path: /var/task

2023-03-01T16:31:12.159+01:00	START RequestId: c497c0cb-a7e7-49e3-b289-f924b17fd4ab Version: $LATEST

2023-03-01T16:31:12.451+01:00

Copy
2023-03-01T15:31:12.450Z	c497c0cb-a7e7-49e3-b289-f924b17fd4ab	fail	System.NullReferenceException: Object reference not set to an instance of an object.
2023-03-01T15:31:12.450Z c497c0cb-a7e7-49e3-b289-f924b17fd4ab fail System.NullReferenceException: Object reference not set to an instance of an object.

What should I check and how to fix it?

Answer

This is most commonly caused by referencing a null object in your code. For Example:

public class MyClass
{
public int id {get; set;}
}

MyClass myClass;
myClass.Id = 0;     // Null reference because it has not been instantiated.

//Working code
MyClass myClass = new MyClass(); // new MyClass(); instantiates the object.
myClass.Id = 0; // Works because the myClass has been instantiated.

Since you say it works locally, Could there be a permission missing on lambda that is preventing an object from instantiating like it normally would with your local permissions? I would check that first.

NET 6 REST API Service as a Lambda: error during the query

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