任务的返回类型<type>在 ASP.NET 核心控制器中</type>

Question

I have a method in my

BaseController

public async Task<BaseModel> PopulateBaseModelAsync(BaseModel m)
{
    m.CreatedDate = DateTime.Now;
    m.CreatedById = await _userManager.GetUserAsync(User);
    m.CreatedByUsername = User.Identity.Name;
    return m;
}

It's forced to be an async Task because of the _userManager.GetUserAsync method.

In a derived controller I want to pass in an BaseModel and have those three properties populated eg

DerivedController

public async Task<IActionResult> CategoriesCreateAsync(BookingCategory bc)
{
    if(bc != null)
    {
        bc = (BookingCategory)PopulateBaseModelAsync(bc);
        _context.BookingCategories.Add(bc);
        _context.SaveChanges();
    }
    return RedirectToAction(nameof(CategoriesIndex));
}

I originally wanted PopulateBaseModel(BaseModel) to just return a new BaseModel eg below, but because of the forced async method I'm not sure how to achieve this.

Original aim

BaseController

    public BaseModel PopulateBaseModel(BaseModel m)
    {
        m.CreatedDate = DateTime.Now;
        m.CreatedById = _userManager.GetUser(User); // Must use async :(
        m.CreatedByUsername = User.Identity.Name;
        return m;
    }

DerivedController

    public IActionResult CategoriesCreate(BookingCategory bc)
    {
        if(bc != null)
        {
            bc = (BookingCategory)PopulateBaseModel(bc);
            _context.BookingCategories.Add(bc);
            _context.SaveChanges();
        }
        return RedirectToAction(nameof(CategoriesIndex));
    }

My main issue is I don't really understand how Task works - the method

public async Task<BaseModel> PopulateBaseModelAsync(BaseModel m)

allows me to return BaseModel but it won't compile because it can't convert Task<BaseModel> to BookingCategory

Answer 1

Your just missing an await :

public async Task<IActionResult> CategoriesCreateAsync(BookingCategory bc)
{
    if(bc != null)
    {
        await PopulateBaseModelAsync(bc);
        _context.BookingCategories.Add(bc);
        _context.SaveChanges();
    }
    return RedirectToAction(nameof(CategoriesIndex));
}

Because PopulateBaseModelAsync returns a Task<IBaseModel> you need to await it's completion.

Here the Task represents an I/O operation, who's result isn't immediately available.

Without awaiting the Task , your method would continue before the result is obtained.

No need to re-assign to bc either, because PopulateBaseModelAsync is modifying the instance it references.