asp.net中的数据校验

Question

在设计中，我有两个文本框，两个图像按钮和一个日历，两个图像按钮在页面加载中单击事件，我在两个文本框中显示今天的日期，Page_load如下所示；

txtfrdate.Text = Convert.ToDateTime(Today()).ToString("dd/MM/yyyy")
txttodate.Text = Convert.ToDateTime(Today()).ToString("dd/MM/yyyy")

现在我只更改txttodate的值(现在的日期大于开始的日期)，然后单击按钮消息应该显示"From Date应该大于date“，我编写了imagebutton1，2单击事件如下

Protected Sub ImageButton1_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles ImageButton1.Click
  Calendar1.Visible = True
  Calendar1.SelectedDates.Clear()
  Session("click") = 1
End Sub

Protected Sub ImageButton2_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles ImageButton2.Click
    Calendar1.Visible = True
    Calendar1.SelectedDates.Clear()
    Session("click") = 2
End Sub

在日历中选择更改事件

Protected Sub Calendar1_SelectionChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles Calendar1.SelectionChanged
    Select Case (Session("click"))
        Case 1 : txtfrdate.Text = Convert.ToDateTime(Calendar1.SelectedDate.ToShortDateString).ToString("dd/MM/yyyy")
            Session("fd") = Calendar1.SelectedDate
        Case 2 : txttodate.Text = Convert.ToDateTime(Calendar1.SelectedDate.ToShortDateString).ToString("dd/MM/yyyy")
            Session("td") = Calendar1.SelectedDate
    End Select
    Calendar1.Visible = False

    Label4.Visible = False
End Sub

单击视图按钮后，我将检查日期，如下所示

If txtfrdate.Text = "" Then
    Label4.Visible = True
    Label4.Text = "Select From Date"
ElseIf txttodate.Text = "" Then
    Label4.Visible = True
    Label4.Text = "Select To Date"
ElseIf txtfrdate.Text > txttodate.Text Then
    Label4.Visible = True
    Label4.Text = "From Date Must be Smaller than To Date"

实际上，我的问题是，当我只更改txttodate和todate大于from date时，显示日期的消息仍然应该大于日期“我的输出正在显示。

From Date: 31/08/2012  - i am not changing current date during page load
To Date: 29/09/2012 - changing by selecting the calendar message is showing

从日期起必须小于日期

请帮我谢谢大家

Answer 1

虽然我不太确定我是否完全理解你的问题。我不认为这是为了比较两个字符串？txtfrdate.Text > txttodate.text比较字符串值，而不比较dateTime对象！

使用此示例并根据您的需求对其进行调整，以检查dateTime值。

    DateTime dtFrom = DateTime.Now;
    DateTime dtTo = DateTime.Now.Subtract(new TimeSpan(5, 0,0,0));

    if (dtFrom > dtTo)
    {
        Debug.WriteLine("Invalid To-Date");
    }
    else
    {
        Debug.WriteLine("OK");
    }