Cannot convert type SomeClass to 'T'

以下代码会出问题：

public static T Protect<T>(Func<T> func, UserLevel pageRole) where T : ActionResult, new()
{
    try
    {
        return func();
    }
    catch (Exception err)
    {
        if (typeof(T) is JsonResult)
        {
            return (T)new JsonResult() ;

}
        else if (typeof(T) is ActionResult)
        {
            return (T)new ContentResult();
        }

throw err;
    }
}

得到 Cannot convert type 'JsonResult'  to 'T'，应该修正为：

return (T)(object)new JsonResult();

Well, you can always placate the compiler by adding an object cast in the middle:

geoConfigs = (T)(object)GetGeoConfigurationNumericFromDB(items, maMDBEntities);

which will defer the type-check until runtime. However! There is no compiler way to do this otherwise, as it is never going to be happy with string tests like "MamConfiguration". Also, generics work well when the code is ... generic - i.e. does the same thing which each type. The code shown is the opposite of generic. It is non-generic code exposed through a generic API. It is always going to be messy inside. Personally I would try to avoid this usage in the first place.

或者：

You should be able to just use Convert.ChangeType() instead of your custom code:

public T Get<T>(Stats type) where T : IConvertible
{
    return (T) Convert.ChangeType(PlayerStats[type], typeof(T));
}