1

我正在尝试编写一个 try/catch，但显然失败了。我不确定我是否完全理解 try/catch，但我确实知道我很难理解我需要发生的事情，以验证输入的日期是否正确，通过表单提交。我的意思是，我认为它需要是 DateTime 格式，而不是字符串，并且应该是 (MM/dd/yyyy)，但是这个 try/check 事情让我陷入了循环。

说明：返回到您在 frmPersonnel 代码中添加的验证代码，并添加带有逻辑的 try/catch 以防止无效日期导致服务器错误。

代码： 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class frmPersonnel : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        btnSubmit.Click += new EventHandler(this.btnSubmit_Click);//event for button
    }

    private void btnSubmit_Click(object sender, EventArgs e)
    {
//DECLARATIONS
        int count = 0;
        string Msg = "You must enter a value in the following fields: <br/>  ";
        Boolean validatedState = true;
        Boolean validateEntry = false;
        DateTime endDate = new DateTime(2016, 03, 01);
        DateTime startDate = new DateTime(2016, 03, 01);


//BEGIN SERIES OF IF/ELSE FOR CONFIRMING ENTRIES         
        if (Request["txtFirstName"].ToString().Trim() == "")
            {
            //displays yellow bg for missing input
            txtFirstName.BackColor = System.Drawing.Color.Yellow;
            Msg = Msg + "First Name <br/> ";
            }//endif
        else
        {
            txtFirstName.BackColor = System.Drawing.Color.White; 
            count += 1;
        }//end else

        if (Request["txtLastName"].ToString().Trim() == "")
        {
            //displays yellow bg for missing input
            txtLastName.BackColor = System.Drawing.Color.Yellow;
            Msg = Msg + "Last Name <br/> ";
        }//endif
        else
        {
            txtFirstName.BackColor = System.Drawing.Color.White; 
            count += 1;
        }//end else

        if (Request["txtPayRate"].ToString().Trim() == "")
        {
            //displays yellow bg for missing input
            txtPayRate.BackColor = System.Drawing.Color.Yellow;
            Msg = Msg + "Pay Rate <br/>  ";
         }//endif
        else
        {
            txtFirstName.BackColor = System.Drawing.Color.White; 
            count += 1;
        }//end else

        if (Request["txtStartDate"].ToString().Trim() == "")
        {
            //displays yellow bg for missing input
            txtStartDate.BackColor = System.Drawing.Color.Yellow;
            validateEntry = false;
            Msg = Msg + "Start Date <br/>  ";
        }//endif
        else
        {
            try
                {
                //Conversion to DateTime format?
                startDate = DateTime.Parse(Request["txtStartDate"]);
                //How do I write the format I want, and when it should be checked?
                }
            catch (Exception ex)
                {
                //Exception should be caught here, not sure how to write this out though?
                }
            validateEntry = true;
        }//end else

        if (Request["txtEndDate"].ToString().Trim() == "")
        {
            //displays yellow bg for missing input
            txtEndDate.BackColor = System.Drawing.Color.Yellow;
            validateEntry = false;
            Msg = Msg + "End Date <br/>  ";
         }//endif
        else
        {
            try
            {
                //Conversion to DateTime format?
                endDate = DateTime.Parse(Request["txtEndDate"]);
                //How do I write the format I want, and when it should be checked?
            }
            catch (Exception ex)
            {
                //Exception should be caught here, not sure how to write this out though?
            }
            validateEntry = true;

        }//end else
//END SERIES OF IF/ELSE FOR CONFIRMING ENTRIES 

//START IF VALIDATE ENTRY    
        if (validateEntry == true)
        {
            if (DateTime.Compare(startDate, endDate) >= 0)
            {
                txtStartDate.BackColor = System.Drawing.Color.Yellow;
                txtEndDate.BackColor = System.Drawing.Color.Yellow;
                Msg = Msg + "Start Date <br/>" + "End Date <br/> <br/>The end date must be a later date than the start date.";
                //The Msg text will be displayed in lblError.Text after all the error messages are concatenated
                validatedState = false;
                //Boolean value - test each textbox to see if the data entered is valid, if not set validState=false. 
                //If after testing each validation rule, the validatedState value is true, then submit to frmPersonnelVerified.aspx, if not, then display error message
            }
            else //goes to this if dates are correct
            {
                validatedState = true;
                count += 2;
                txtStartDate.BackColor = System.Drawing.Color.White;
                txtEndDate.BackColor = System.Drawing.Color.White;
            }
        }
//END IF VALIDATE ENTRY

//SENDS DATA & ERROR MESSAGES
        if (count == 5 && validatedState == true)
        {
            Session["txtFirstName"] = txtFirstName.Text;
            Session["txtLastName"] = txtLastName.Text;
            Session["txtPayRate"] = txtPayRate.Text;
            Session["txtStartDate"] = txtStartDate.Text;
            Session["txtEndDate"] = txtEndDate.Text;
            Response.Redirect("frmPersonnelVerified.aspx");
            //sends to other page
        }
        else
        {
            //Writes out error messages
            Response.Write("<br/><span style = 'color: red ; position: absolute; top: 360px; left: 90px;'>" + Msg + "</span>");           
        }
//ENDS DATA AND ERROR MESSAGES


    }//end Function: private void BtnSubmit_click...

}
4

4 回答 4

2

将validateEntry = true;移到 内，try这样即使DateTime.Parse抛出异常也不会设置它。你try-catch的s很好。他们将捕获DateTime.Parses 中的任何错误。

于 2016-08-02T19:52:31.587 回答
2

来自 MSDN：https ://msdn.microsoft.com/en-us/library/0yd65esw.aspx

引发异常时，公共语言运行时 (CLR) 会查找处理此异常的 catch 语句。如果当前执行的方法不包含这样的 catch 块，则 CLR 会查看调用当前方法的方法，并在调用堆栈中以此类推。如果未找到 catch 块，则 CLR 向用户显示未处理的异常消息并停止程序的执行。

try 块包含可能导致异常的受保护代码。该块一直执行，直到抛出异常或成功完成。

你可以从逻辑上想到一个 try...catch... 块有点像条件。

例如，假设您有以下代码：

string someString = "ABC";
DateTime someDate = DateTime.Parse(someString);

显然“ABC”不是有效的日期时间，那么会发生什么？您的应用程序由于未处理的异常（错误）而崩溃。

当您将某些内容包装在 try...catch... 块中时，您基本上是在说：

如果我的 try 块中发生异常，则停止执行 try 块中的代码，执行 catch 块中的代码，然后像什么都没发生一样继续。否则，只需忽略我的 catch 块中的代码。

这称为结构化异常处理。您正在预测代码的“危险”区域，并添加应急代码以防最坏的情况发生。结构化异常处理对于处理不安全的用户输入以及外部或不可靠的系统（如外部 Web 服务）特别有用。

一个例子：

string someString = "ABC";
DateTime someDate;

try
{
    someDate = DateTime.Parse(someString);
}
catch
{
    // someString must not have been a valid DateTime!
    // Console.WriteLine($"Hey, {someString} is not a valid DateTime!"); 
    Console.WriteLine(String.Format("Hey, {0} is not a valid DateTime!", someString)); 
}

// Code continues executing because the exception was "caught"
于 2016-08-02T19:47:43.750 回答
2

您可以使用 TryParse 检查有效日期

// valid Date
DateTime goodDate;
if (DateTime.TryParse("2000-02-02", out goodDate))
{
    Console.WriteLine(goodDate);
}

// not a date
DateTime badDate;
if (DateTime.TryParse("???", out badDate))
{
    Console.WriteLine(badDate);
}
else
{
    Console.WriteLine("Invalid");
}

如果您期望基于区域的格式，您可能还希望包含文化

string dateString;
      CultureInfo culture;
      DateTimeStyles styles;
      DateTime dateResult;    
// Parse a date and time with no styles.
      dateString = "03/01/2009 10:00 AM";
      culture = CultureInfo.CreateSpecificCulture("en-US");
      styles = DateTimeStyles.None;
      if (DateTime.TryParse(dateString, culture, styles, out dateResult))
         Console.WriteLine("{0} converted to {1} {2}.", 
                           dateString, dateResult, dateResult.Kind);
      else
         Console.WriteLine("Unable to convert {0} to a date and time.", 
                           dateString);
于 2016-08-02T19:43:59.463 回答
1

如果你真的想准确：

        DateTime dateValue;

        var isDatePass = DateTime.TryParseExact("03/08/2002", "MM/dd/yyyy", new CultureInfo("en-US"), DateTimeStyles.None, out dateValue);

请记住，您始终可以使用预先验证。

于 2016-08-02T19:44:08.173 回答