Unable to map nullable primitive types (string? to bool?) using custom MapWith delegate

What am I missing?

using Mapster;
using MapsterMapper;

TypeAdapterConfig config = new TypeAdapterConfig();
config.NewConfig<string?, bool?>().MapWith(src => Helper.ParseToNullableBool(src));
config.Compile();

Mapper mapper = new Mapper(config);

Source source = new Source { Prop1 = "yes" };
Destination destination = mapper.Map<Destination>(source);

Console.ReadLine();

static class Helper
{
    public static bool? ParseToNullableBool(string? value)
    {
        if (string.IsNullOrWhiteSpace(value))
            return null;

        return value.Trim().ToLower() switch
        {
            "true" or "t" or "yes" or "1" => true,
            "false" or "f" or "no" or "0" => false,
            _ => null
        };
    }
}

class Source
{
    public string? Prop1 { get; set; }
}

class Destination
{
    public bool? Prop1 { get; set; }
}

converting non-nullable string to non-nullable bool works fine

@vzalamea

@vzalamea What Version of Mapster you using?

works in 10.0.8. broken in 10.0.9

in 10.0.9 Nullable can using not nullable Mapping settings. Try using this:

config.NewConfig<string, bool>().MapWith(src => Helper.ParseToNullableBool(src));

class Source
{
    public string? Prop1 { get; set; }
}

class Destination
{
    public bool? Prop1 { get; set; }
}

I'm seeing the same issue.

I have a global converter:

TypeAdapterConfig.GlobalSettings
    .ForType<DateTime?, long?>()
    .MapWith(src => src.ToSecondsTimestamp());

Source:

public DateTime? CreatedAt { get; set; }

Destination:

public long? CreatedAt { get; set; }

Calling:

var dto = entity.Adapt<TimeLogExtendRsRes>();

throws:

System.InvalidOperationException: Nullable object must have a value.

@nghiaphamhn

Hi, @nghiaphamhn This is due to the addition of support for using mapping settings for ValueType when mapping its Nullable representations: .Adapt<DateTime?, long?>(), .Adapt<DateTime, long?>() , .Adapt<DateTime?, long>()
will automatically use the settings for ForType<DateTime, long> unless you specify a more specific equivalent: .ForType<DateTime?, long?>() or .ForType<DateTime, long?>() or .ForType<DateTime?, long>().

This was the original idea, but it seems there were problems with the prioritization of settings.

Your case should work correctly in version 10.0.10 If you don't have a custom converter installed for .ForType<DateTime, long>(), it will still have higher priority. It will be fixed in the next version.

@DocSvartz

Thanks for the explanation, @DocSvartz

In my case, I explicitly configured converters for all nullable and non-nullable combinations:

GlobalConfig.ForType<DateTime, long>().MapWith(src => (long)src.ToSecondsTimestamp());
GlobalConfig.ForType<DateTime?, long>().MapWith(src => (long)src.ToSecondsTimestamp());
GlobalConfig.ForType<DateTime, long?>().MapWith(src => src.ToSecondsTimestamp());
GlobalConfig.ForType<DateTime?, long?>().MapWith(src => src.ToSecondsTimestamp());
GlobalConfig.ForType<long, DateTime>().MapWith(src => src.FromUnixTimeStamp());
GlobalConfig.ForType<long, DateTime?>().MapWith(src => src.FromUnixTimeStamp());
GlobalConfig.ForType<long?, DateTime>().MapWith(src => (DateTime)src.FromUnixTimeStamp());
GlobalConfig.ForType<long?, DateTime?>().MapWith(src => src.FromUnixTimeStamp());

Just to clarify, I'm currently using Mapster 10.0.10, and the issue still occurs with my configuration.
The same configuration works correctly on 10.0.8. The issue only appears after upgrading to 10.0.9 and 10.0.10.

@nghiaphamhn

@nghiaphamhn I think I understood what the problem is.

GlobalConfig.ForType<DateTime?, long>().MapWith(src => (long)src.ToSecondsTimestamp());

it is valid only DateTime is not null
Otherwise, you will get the error you are talking about: System.InvalidOperationException: Nullable object must have a value.

It's safer to use this:

src.ToSecondsTimestamp().GetValueOrDefault();

I think this will also be fixed and will work as before.

fix: #992 and #996 (#999)

@DocSvartz

Thanks @DocSvartz , this solution works correctly now:

src.ToSecondsTimestamp().GetValueOrDefault();

The Nullable object must have a value error is no longer occurring.

Navigation Menu

Repository navigation

Unable to map nullable primitive types (string? to bool?) using custom MapWith delegate #992

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Unable to map nullable primitive types (string? to bool?) using custom MapWith delegate #992

Description

Activity

DocSvartz commented on Jun 25, 2026

vzalamea commented on Jun 25, 2026

DocSvartz commented on Jun 25, 2026

nghiaphamhn commented on Jul 13, 2026

DocSvartz commented on Jul 14, 2026

nghiaphamhn commented on Jul 14, 2026

nghiaphamhn commented on Jul 14, 2026

DocSvartz commented on Jul 14, 2026

nghiaphamhn commented on Jul 20, 2026

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions