GraphQL–DotNet - The type: Guid cannot be coerced effectively to a GraphQL type

I’m spending a lot (read: “waaay to many”) time learning GraphQL. One of the things I had to figure out was how to use Guids inside my GraphQL schema.

On one of my projects we are using Guids. Here is the mapping I tried to use:

	public class Product
	{
	public Guid Id {get;set;}
	public string Description {get;set;}
	}

view raw Product.cs hosted with ❤ by GitHub

	public class ProductType:ObjectGraphType<Product>
	{
	public ProductType()
	{
	Field(m => m.Id);
	Field(m => m.Description);
	}
	}

view raw ProductType.cs hosted with ❤ by GitHub

When loading my GraphQL endpoint this resulted in the following error message:

	public class Product
	{
	public Guid Id {get;set;}
	public string Description {get;set;}
	}

view raw Product.cs hosted with ❤ by GitHub

	public class ProductType:ObjectGraphType<Product>
	{
	public ProductType()
	{
	Field(m => m.Id);
	Field(m => m.Description);
	}
	}

view raw ProductType.cs hosted with ❤ by GitHub

The type: Guid cannot be coerced effectively to a GraphQL type

To fix it I had to explicitly specify the FieldType as IdType:

	public class ProductType:ObjectGraphType<Product>
	{
	public ProductType()
	{
	Field(m => m.Id, type: typeof(IdGraphType));
	Field(m => m.Description);
	}
	}

view raw ProductTypeFixed.cs hosted with ❤ by GitHub