Question

错误在Create（）函数

中

创建（）
错误1'MvcAnketaIT.Controllers.SurveyController.Create（）'：并非所有代码路径都返回值

代码

public ActionResult Create()
    {
        int myId = getIdByUser(this.User.Identity.Name);
        if (this.User.Identity.IsAuthenticated)
        {

            if (myId == -1) //no questionnaire in db           
            {
                     SurveyModel survey = new SurveyModel();
                     ViewBag.userName = this.User.Identity.Name;
                     ViewBag.Q3Sex = new SelectList(db.Genders, "ID", "gender");
                     ViewBag.Q8Question1 = new SelectList(db.Questions1, "Id", "Technology");
                     ViewBag.Q9Question2_1 = new SelectList(db.Satisfaction, "ID", "Name");
                     ViewBag.Q10Question2_2 = new SelectList(db.Satisfaction, "ID", "Name");
                     ViewBag.Q11Question2_3 = new SelectList(db.Satisfaction, "ID", "Name");
                     ViewBag.Q12Question2_4 = new SelectList(db.Satisfaction, "ID", "Name");
                     ViewBag.Q13Question2_5 = new SelectList(db.Satisfaction, "ID", "Name");
                     ViewBag.Q14Question2_6 = new SelectList(db.Satisfaction, "ID", "Name");
                     ViewBag.Q15Question2_7 = new SelectList(db.Satisfaction, "ID", "Name");
                     ViewBag.Q16Question2_8 = new SelectList(db.Satisfaction, "ID", "Name");
                     ViewBag.Q17Question3 = new SelectList(db.Questions3, "ID", "Solve");
                     ViewBag.Q19Question5 = new SelectList(db.Questions5, "ID", "No_Contacts");
                     ViewBag.Q20Question6 = new SelectList(db.Questions6, "ID", "Recommendation");
                     return View();

            }
        }

         else //user already has a questionnaire fulfilled
            {
                return RedirectToAction("Edit/" + myId); //redirect to the right id of the user
            }
    }

Answer 1

您在if块内声明了一个变量：

if (something)
{
    int myId = getIdByUser(this.User.Identity.Name);
}
else
{
    // myId doesn't exist here.
}

因此该变量只能在该块的范围内访问。要在更大的范围内使用它，需要在块之外声明它：

int myId;
if (something)
{
    myId = getIdByUser(this.User.Identity.Name);
}
else
{
    // myId is accessible here
    // though runs the risk of not having been set to anything
    // depending on whether or not the if condition was met
}

修改：您在问题中添加的内容是完全不同的问题。但消息很清楚。并非所有代码路径都返回值。你所拥有的结构可以简化为：

if (something)
{
    if (something_else)
    {
        return;
    }
}
else
{
    return;
}

如果something为真，会发生什么，但something_else不是？没有达到return语句。因此，该函数不返回任何内容。这会导致编译器错误。您需要在每个代码路径中从函数返回一些内容。在这种情况下，这里：

if (something)
{
    if (something_else)
    {
        return;
    }
    // Need to return a value here
}
else
{
    return;
}

Answer 2

问题在于变量的范围 - 在IF块中声明了myID，并且您正尝试在ELSE块中使用它。

else块不知道这个变量，这是你得到的错误信息。

Answer 3

myId必须在if块之外定义，就像在else中一样，你还没有声明它。请尝试使用此版本2：

public ActionResult Create()
{
    int myId = getIdByUser(this.User.Identity.Name);
    if (this.User.Identity.IsAuthenticated)
    {
        if (myId == -1) //no questionnaire in db           
        {
            SurveyModel survey = new SurveyModel();          
            return View();         
        }
    }   
    else //user already has a questionnaire fulfilled
    {
        //redirect to the right id of the user
        return RedirectToAction("Edit/" + myId); 
    }
    return View();
}

下面的代码中的表达式术语错误无效

3 个答案: