在 IF Else 中控制自定义消息

Question

我开发了文本框来添加日期范围以选择该日期范围内的特定记录。 我已经为此编写了 IF ELSE，如果两个文本框都为空，则显示错误消息，但问题是当我第一次调用页面时，它会显示相同的错误。我知道为什么，因为在第一次尝试文本框是空的，但如何控制呢？

public ActionResult ShowMyAtdByDate(String DateFrom, String DateTo) 
    {
        int empId = 0;
        int.TryParse((string)Session["Employee"], out empId); // parse variable to int and saves the result in empId
     //   IEnumerable<GetMyAtd_DateResult> MyAtdRecord = DataContext.GetMyAtd_Date(DateFrom,DateTo,empId).ToList();

        if (DateFrom != "" && DateTo == "" && empId > 0)
        {
            IEnumerable<GetMyAtd_DateResult> MyAtdRecord = DataContext.GetMyAtd_Date(DateFrom,null, empId).ToList();
            ViewBag.Dates = "Records for" + " " + DateFrom;
            return View(MyAtdRecord);

        }
        else if (DateFrom == "" && DateTo != "" && empId > 0)
        {
            IEnumerable<GetMyAtd_DateResult> MyAtdRecord = DataContext.GetMyAtd_Date( null, DateTo, empId).ToList();
            ViewBag.Dates = "Records for" + " " + DateTo;
            return View(MyAtdRecord);
        }
        else if (DateFrom != "" && DateTo != "" && empId > 0)
        {
            IEnumerable<GetMyAtd_DateResult> MyAtdRecord = DataContext.GetMyAtd_Date(DateFrom, DateTo, empId).ToList();
            ViewBag.Dates = "Records from" + " " + DateFrom + " " + "to" + " " + DateTo;
            return View(MyAtdRecord);
        }
        else if (DateFrom == "" && DateTo == "" && empId > 0)
        {
            IEnumerable<GetMyAtd_DateResult> MyAtdRecord = DataContext.GetMyAtd_Date(null, null, empId).ToList();
            ViewBag.Dates = "No dates selection";
            return View(MyAtdRecord);
        }
        else if(empId <=0 )
        {
            return RedirectToAction("IsAuth_Page","Home");
        }

        return View();


    }

查看：

@{

     var grid = new WebGrid(ViewData.Model, rowsPerPage: 25);

 }

 @if (Model.Count > 0)
 {
     <div id="AllMyAtd_ByDate">
       @grid.GetHtml(columns: grid.Columns(
                                        grid.Column("EmplID", "Employee ID"),
                                        grid.Column("EmplName", "Employee Name"),
                                        grid.Column("ShiftID", "Shift ID"),
                                        grid.Column("DateVisited", "Date of Visit"),
                                        grid.Column("InTime", "In Time"),
                                        grid.Column("TimeOut", "Time Out"),
                                        grid.Column("OverTime", "Over Time"),
                                        grid.Column("TotalWorkingTime", "Total Working Time")
                                      ))
     </div>
 }
 else
 {
     <h4 class="error">Sorry Record Doesn't Exist for selected date(s)</h4>  
 }

当我第一次浏览到这个页面时，它会出现，实际上只有当我将两个文本框都留空时才会出现。

Answer 1

用户第一次进入这个页面时，它将是一个 GET 请求。您可以从 GET 方法中删除此逻辑（因为它不需要在第一次执行时执行）并将其放入 POST 方法中，因为这是在用户已提交表单。

---

[HttpGet]
public ActionResult ShowMyAtdByDate()
{
    int empId = 0;
    int.TryParse((string)Session["Employee"], out empId);

    if (empId <= 0)
    {
        return RedirectToAction("IsAuth_Page", "Home");
    }

    return View();
}

[HttpPost]
public ActionResult ShowMyAtdByDate(string dateFrom, string dateTo)
{
    if (dateFrom != "" && dateTo == "" && empId > 0)
    {
        ...
    }
    else if (dateFrom == "" && dateTo != "" && empId > 0)
    {
        ...
    }
    etc...
}

并确保在您的视图中您的表单具有 POST 方法