Can't assign null value to a double? property in AutoMapper

Question

I'm using AutoMapper and one line causes an error when I try to assign null in ternary operator like this:

.ForMember(dest => dest.VatCategoryTaxAmount, 
           opt => opt.MapFrom(src => src.TaxSubtotal != null && 
                                     src.TaxSubtotal.TaxCategory != null 
                                     ? double.Parse(src.TaxSubtotal.TaxCategory.Percent) 
                                     : null));

Error:

Cannot convert anonymous method block to type 'type' because it is not a delegate type

When I use 0 instead of null, then it works.

I'm confused because the destination property is of type double?. I want to assign to it a null value.

How can I do that?

Answer 1

The problem is your conditional assignment doesn't return the same type.

src.TaxSubtotal.TaxCategory != null ? double.Parse(src.TaxSubtotal.TaxCategory.Percent) : null

it returns a double if true or null if false. Try to cast the true assignment to a nullable.