asp.net - 难倒用户控件上的自定义属性

Question

我创建了一个 ASP.NET 用户控件。当我明确提供自定义属性的值时，该值将传递给控件。但是，当我尝试使用数据源中的值时，该值不会传递给控件。

用户控件位于 FormView 中。 FormView 成功显示基础记录。我试图将 FormView 数据源中列中的值传递给控件。这有效

<asp:formview .... />
<editTemplate>
<uctrl:DateSelector ID="DateSelector1" runat="server" DateValue="5/30/2011" /><br /> 
<%#Eval("MilestoneDate")%>    
</editTemplate>
</asp:formview>

这不...

<asp:formview .... />
<editTemplate>
<uctrl:DateSelector ID="DateSelector1" runat="server" DateValue='<%#Eval("MilestoneDate")%>' /><br /> 
<%#Eval("MilestoneDate")%>   
</editTemplate>
</asp:formview>

我已经确认 MileStoneDate 确实有它的值(value)。无论出于何种原因，该值并未传递给控件，​​但控件确实识别出文字值。

Imports Microsoft.VisualBasic 
Imports System.Data 
Imports System.Data.SqlClient 
Imports System.Web.UI 
Imports System.ComponentModel 

Partial Class content_WebUserControl 
    Inherits System.Web.UI.UserControl 
    <Bindable(True, BindingDirection.OneWay)> 
    Public Property DateValue() As String 
        Get 
            Return _DateValue 
        End Get 
        Set(ByVal value As String) 
            _DateValue = value 
        End Set 
    End Property 
    Private _DateValue As String 
    Protected Sub Page_Load() Handles Me.Load 

        If IsDate(Me.DateValue) Then 
            Dim NewDate As DateTime = CDate(Me.DateValue) 
            LabelSelectedDateDisplay.Text = Me.DateValue 
            LabelSelectedDateDisplay_DayOfWeek.Text = NewDate.ToString("dddd") 
            TextBoxSelectedDate.Text = Me.DateValue 
        Else 
            LabelSelectedDateDisplay.Text = "" 
            LabelSelectedDateDisplay_DayOfWeek.Text = "" 
            TextBoxSelectedDate.Text = "" 
        End If 

    End Sub 


End Class

我被引用到这个 URL 上的帖子 ASP.NET User Control : can't initialize a user control property using Eval("...")

但是，根据我对这篇文章的理解，我所拥有的应该是有效的。

Answer 1

您需要使用 ViewState 在页面请求之间保留 DateValue。

Public Property DateValue() As String 
   Get 
        IF IsNothing(ViewState("datevalue") Then
           return String.Empty
        End If
        return ViewState("datevalue").ToString()
   End Get 
   Set(ByVal value As String) 
       ViewState("datevalue")=value
   End Set 
End Property 

或将值直接存储到控件:

 Public Property DateValue() As String 
    Get 
          Return LabelSelectedDateDisplay.Text
    End Get 
    Set(ByVal value As String) 
      If IsDate(value) Then 
            Dim NewDate As DateTime = CDate(value) 
            LabelSelectedDateDisplay.Text = NewDate 
            LabelSelectedDateDisplay_DayOfWeek.Text = NewDate.ToString("dddd") 
            TextBoxSelectedDate.Text = NewDate 
        Else 
            LabelSelectedDateDisplay.Text = "" 
            LabelSelectedDateDisplay_DayOfWeek.Text = "" 
            TextBoxSelectedDate.Text = "" 
        End If          
    End Set 
End Property