asp.net - DataList 内的用户控件

Question

我在DataList中有一个UserControl，我根据DataList数据的PrimeryKey填充用户控件内的控件。第一次加载程序的行为符合预期，但当用户更改页面索引时，所有 MessageID 返回 0，最有可能的值是 <%# Eval("id").toString()%> 丢失。我不想对用户控件进行硬编码，因为我在项目的很多地方都使用了它，这使得代码可维护。我该如何纠正这种行为？提前致谢。

我的代码如下:

        <asp:DataList ID="DataList1" runat="server" Width="658px">
            <ItemTemplate>
                <table style="width: 100%;">
                    <tr>
                        <td style="font-weight: 700; color: #FF0000; font-size: medium; font-size: 10pt; font-family: Tahoma">
                            <%# Eval("hadding") +" ["+Eval("startTime")+" - "+Eval("endTime")+"]"%>
                        </td>
                    </tr>
                    <tr>
                        <td style="font-weight: 700; font-size: 10pt; font-family: Tahoma">
                            <%# Eval("location") %>
                        </td>
                    </tr>                        
                    <tr>
                        <td>
                            <uc1:MyUserControl ID="MyUserControl1" runat="server" MessageID='<%# Eval("id").toString()%>' />
                        </td>
                    </tr>
                </table>

            </ItemTemplate>
        </asp:DataList>
        <table>
            <tr>
                <td>
                    <asp:Button ID="btnfirst" runat="server" Font-Bold="true" Text="<<" Height="31px"
                        Width="43px" OnClick="btnfirst_Click" /></td>
                <td>
                    <asp:Button ID="btnprevious" runat="server" Font-Bold="true" Text="<" Height="31px"
                        Width="43px" OnClick="btnprevious_Click" /></td>
                <td>
                    <asp:Button ID="btnnext" runat="server" Font-Bold="true" Text=">" Height="31px"
                        Width="43px" OnClick="btnnext_Click" /></td>
                <td>
                    <asp:Button ID="btnlast" runat="server" Font-Bold="true" Text=">>" Height="31px"
                        Width="43px" OnClick="btnlast_Click" /></td>
            </tr>
        </table>

和我的用户控件:

Partial Class MyUserControl
  Inherits System.Web.UI.UserControl

  Private _messageID As Integer

  Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If (_messageID > 0) Then
        Fill(_messageID)
    End If
  End Sub


  Public Property MessageID As Integer
    Get
        Return _messageID
    End Get
    Set(value As Integer)
        _messageID = value
    End Set
  End Property

  Protected Sub Fill(messageID As Integer)
    'Some code
  End Sub

End Class

Answer 1

如果不查看整个页面生命周期就很难回答，但您可以尝试将 MessageId 存储在控件的 ViewState 中，如下所示:

  Public Property MessageID As Integer
    Get
      If (Me.ViewState("VSMessageID") IsNot Nothing) Then
         return CType(Me.ViewState("VSMessageID "), Integer)
      else 
         return 0 // arbitrary value
    End Get

    Set(value As Integer)
       Me.ViewState.Add("VSMessageID", value)
    End Set
  End Property

然后:

  Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If (MessageID > 0) Then
        Fill(MessageID )
    End If
  End Sub

参见http://msdn.microsoft.com/en-us/library/ms227551%28v=vs.85%29.aspx?cs-save-lang=1&cs-lang=vb#code-snippet-1

抱歉，VB.Net 语法错误