asp.net - MVC中返回View时为"Not all code paths return a value"

Question

如果对象(国家/地区)不为空，我想返回一个 View 。但我收到错误“并非所有代码路径都返回值”

我的代码如下

public ActionResult Show(int id)
{
    if (id != null)
    {
        var CountryId = new SqlParameter("@CountryId", id);
        Country country = MyRepository.Get<Country>("Select * from country where CountryId=@CountryId", CountryId);
        if (country != null)
        {
            return View(country);
        }
    }

}

Answer 1

当您从“if”语句中返回某些内容时，就会发生这种情况。编译器会想，如果“if”条件为假怎么办？这样，即使您在函数中定义了“ActionResult”的返回类型，您也不会返回任何内容。因此在else语句中添加一些默认返回:

public ActionResult Show(int id)
{

    if (id != null)
    {
        var CountryId = new SqlParameter("@CountryId", id);
        Country country = MyRepository.Get<Country>("Select * from country where CountryId=@CountryId", CountryId);

        if (country != null)
        {
            return View(country);
        }
        else
        {
            return View(something);
        }
    }
    else
    {
        return View(something);
    }
}