ASP.NET Web API中AutoMapper未忽略可空布尔值问题排查

问题场景 #

基于.NET 6开发ASP.NET Web API的餐厅信息修改功能，核心实体Restaurant的HasDelivery是非可空布尔类型，请求DTOModifyRestaurantDto中对应属性为可空布尔类型。配置AutoMapper仅映射非null值后，字符串类型属性正常生效，但可空布尔值始终被转为false，未被忽略。

相关代码 #

Restaurant实体类 #

public class Restaurant
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string? Description { get; set; }
    public string Category { get; set; }
    public bool HasDelivery { get; set; }
    public string ContactEmail { get; set; }
    public string ContactNumber { get; set; }

    public int? CreatedById { get; set; }
    public virtual User CreatedBy { get; set; }

    public int AddressId { get; set; }
    public virtual Address Address { get; set; }

    public virtual List<Dish> Dishes { get; set; }
}

ModifyRestaurantDto类 #

public class ModifyRestaurantDto
{
    [MaxLength(25)]
    public string? Name { get; set; }

    [MaxLength(100)]
    public string? Description { get; set; }
    public bool? HasDelivery { get; set; }
}

UpdateAsync方法 #

public async Task UpdateAsync(int id, ModifyRestaurantDto modifyRestaurantDto)
{
    var restaurant = await _dbContext
        .Restaurants
        .FirstOrDefaultAsync(r => r.Id == id)
        ?? throw new NotFoundException("Restaurant not found...");

    var authorizationResult = _authorizationService
        .AuthorizeAsync(
            _userContextService.User,
            restaurant,
            new ResourceOperationRequirement(ResourceOperation.Update))
        .Result;

    if (!authorizationResult.Succeeded) 
        throw new ForbidException();

    _mapper.Map(modifyRestaurantDto, restaurant);
    await _dbContext.SaveChangesAsync();
}

AutoMapper配置 #

public class RestaurantMappingProfile : Profile
{
    public RestaurantMappingProfile()
    {
        CreateMap<ModifyRestaurantDto, Restaurant>()
            .ForAllMembers(opts => opts.Condition((src, dest, value) => value is not null));
    }
}

问题原因 #

问题出在AutoMapper的Condition参数逻辑上：当DTO中的HasDelivery为null时，AutoMapper会先将这个可空布尔值转换为目标属性（非可空bool）的默认值false，再把这个转换后的false传入Condition的value参数中。此时value is not null判断为true，所以会执行映射，将false覆盖到实体的HasDelivery属性上，导致原本的属性值被修改。

解决方案 #

方案一：全局修改判断逻辑，直接检查源属性值 #

修改AutoMapper配置，通过上下文获取源对象的原始属性值，避免转换后的默认值干扰：

public class RestaurantMappingProfile : Profile
{
    public RestaurantMappingProfile()
    {
        CreateMap<ModifyRestaurantDto, Restaurant>()
            .ForAllMembers(opts => opts.Condition((src, dest, _, context) => 
            {
                // 获取源对象当前属性的原始值
                var srcProperty = context.MemberMap.SourceMember;
                var srcValue = srcProperty.GetValue(src);
                return srcValue != null;
            }));
    }
}

方案二：单独针对可空布尔属性配置条件 #

如果只需要处理HasDelivery属性，可单独为其设置判断条件，其他属性保持原有逻辑：

public class RestaurantMappingProfile : Profile
{
    public RestaurantMappingProfile()
    {
        CreateMap<ModifyRestaurantDto, Restaurant>()
            // 仅当源属性有值时才映射HasDelivery
            .ForMember(dest => dest.HasDelivery, opt => 
                opt.Condition(src => src.HasDelivery.HasValue))
            // 其他属性保持原有非null判断
            .ForAllOtherMembers(opts => opts.Condition((src, dest, value) => value is not null));
    }
}

内容的提问来源于stack exchange，提问作者BartTux