consider following code

public async Task<Unit> Handle(UpdateVendorCommand request, CancellationToken cancellationToken)
    {
        var vendor = await _context.Vendor.FindAsync(request.Id);

        if (vendor is null)
            throw new KeyNotFoundException();

        _mapper.Map(request, vendor);
        await _context.SaveChangesAsync();
        return Unit.Value;
    }  

I'm getting status code 200 instead of 204 because I can't return null. How do I return null if my method return type is Task<Unit>? Or is there any alternative beside using Task<Unit>?

My Controller

public class UpdateVendorController : ControllerBase
{
    private readonly IMediator _mediator;

    public UpdateVendorController(IMediator mediator)
    {
        _mediator = mediator;
    }

    [HttpPut]
    [Route("vendor")]
    [SwaggerOperation(Tags = new[] { "Vendor" })]
    public async Task<Unit> UpdateVendor([FromBody] UpdateVendorCommand request)
    {
        return await _mediator.Send(request);
    }
}

CodePudding user response：

For Mediatr, Unit is equivalent to void, not any kind of object that can be nullable.

I'd suggest you change the controller to be more specific in return types:

public async Task<IActionResult> UpdateVendor([FromBody] UpdateVendorCommand request)
{
    _ = await _mediator.Send(request); // Don't care about the return type, it's void
    return NoContent();
}