Ignore nullable property does warning CS8603

.Net 7.0 with nullable enabled

public struct Dest
{
    public string Name { get; set; }
    public string? NullableString { get; set; }
}

public struct Source
{
    public string Name { get; set; }
}

public class Mapping : IRegister
{
    public void Register(TypeAdapterConfig config)
    {
        config.NewConfig<Source, Dest>()
            .Ignore(d => d.NullableString); // this string a got a warning message CS8603: Possible null reference return
    }
}

I think that signature of Ignore method need to be
public TypeAdapterSetter<TSource, TDestination> Ignore(params Expression<Func<TDestination, object?>>[] members);

Any fix for this? How do you ignore a property that is nullable?

@andrerav

@andrerav As far as I understand, this is used to get the Name of the Property.
The value itself is not extracted there.

Ignore(d=> d.NullableString) == Ignore("NullableString").

The proposed solution @nwoolls removes the warning.
Perhaps the original idea using Ignore was something more?

getting same issue.

.Ignore(dest => dest.AccountNumber) //fails/warns with CS8603 when property is nullable.

.Ignore("AccountNumber") //works fine. How expensive is this? Does this not use reflection?

@vzalamea

Hi @vzalamea
.Ignore(dest => dest.AccountNumber) == .Ignore("AccountNumber")

.Ignore(dest => dest.AccountNumber)
This is a helper that gets the Name of the property from the Expression, not the value of that Expression and is more resistant to refactoring in IDE.

Hi @vzalamea .Ignore(dest => dest.AccountNumber) == .Ignore("AccountNumber")

.Ignore(dest => dest.AccountNumber) This is a helper that gets the Name of the property from the Expression, not the value of that Expression and is more resistant to refactoring in IDE.

the problem is when I have <TreatWarningsAsErrors>true</TreatWarningsAsErrors>

If I treat it as just a warning, the code compiles fine and behaves as expected. So I'm not sure why "d.AccountNumber" is being evaluated and not just used to get the property name.

If I treat it as just a warning, the code compiles fine and behaves as expected. So I'm not sure why "d.AccountNumber" is being evaluated and not just used to get the property name.

It occurs because Expressions usually using to obtain the Values of property.
This is precisely what the compiler warns you about. If you try to get the value of this property, you might get null instead of a string.

The fix for this case should be simple, I'll see what I can do.

@DocSvartz

Thank you, @DocSvartz .

It seems this made it into the v10.0.10 release.

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Ignore nullable property does warning CS8603 #520

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Ignore nullable property does warning CS8603 #520

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nwoolls commented on Nov 29, 2024

DocSvartz commented on Jan 23, 2025

vzalamea commented on Jun 23, 2026

DocSvartz commented on Jun 24, 2026

vzalamea commented on Jun 24, 2026

vzalamea commented on Jun 24, 2026

DocSvartz commented on Jun 24, 2026

ramiabughazaleh commented on Sep 4, 2026

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