AutoMapper 没有创建新的映射指南

Question

I am having trouble figuring out how to trigger "new Guid()" using AutoMapper.

This is my model:

public class Countries
{
    public Guid Id { get; set; } = new Guid();
    public string Name { get; set; }
}

And this is my ViewModel:

public class CountriesViewModel
{
    public Guid Id { get; set; }
    public string Name { get; set; }
}

When I map from CountriesViewModel to Countries, Id in Countries have default value of Guid ( which is {00000000-0000-0000-0000-000000000000} ), instead of creating new Guid.

This is how I am doing that mapping:

public async Task<CountriesViewModel> Add(CountriesViewModel country)
{
    var mapped = _mapper.Map<CountriesViewModel, Countries>(country);

    _context.Countries.Add(mapped);

    if (await _context.SaveChangesAsync() == 1)
    {
        _mapper = _countriesConfig.CreateMapper();
        return _mapper.Map<Countries, CountriesViewModel>(mapped);
    }

    return new CountriesViewModel();
}

Answer 1

Here you are creating instance of Guid() that creates an empty Guid ie 00000000-0000-0000-0000-000000000000 every time

You are looking for Guid.NewGuid() which creates new guid with unique value.

Try below

public class Countries
{
    public Guid Id { get; set; } = Guid.NewGuid();
                                  //^^^^^^^^^^This was wrong in your code
    public string Name { get; set; }
}

For reference: Guid.NewGuid() vs. new Guid()