將屬性傳遞到UserControl的問題Asp.Net

Question

我試圖在ASP.NET中創建一個UserControl來顯示基於傳入的兩個值的新聞項，NewsTag和ItemLimit。問題是SQLdatasource沒有拾取SqlDataSource1_Init中的屬性。相反，當調用這個屬性時，對這些屬性的調用是空的，但是在渲染具有值之後。

<script runat="server"> 
    Public Property NewsTag() As String 
     Get 
      Dim o As Object = ViewState("NewsTag") 
      If Not o Is Nothing Then Return CStr(o) Else Return Nothing 
     End Get 
     Set(ByVal value As String) 
      ViewState("NewsTag") = value.Replace(" ", "") 
     End Set 
    End Property 

    Public Property ItemLimit() As String 
     Get 
      Dim o As Object = ViewState("ItemLimit") 
      If Not o Is Nothing Then Return CStr(0) Else Return Nothing 
     End Get 
     Set(ByVal value As String) 
      'Limit news items to 50, for readability 
      ViewState("ItemLimit") = Math.Max(Math.Min(CInt(value), 50), 5) 
     End Set 
    End Property 

    Protected Sub SqlDataSource1_Init(ByVal sender As Object, ByVal e As System.EventArgs) 
     SqlDataSource1.SelectCommand = "SELECT top " + ItemLimit() + " a.[id], a.[itemdate], a.[title], a.[description], a.[photo] FROM [Announcements] a, [NewsInTags] n, [Tags] t WHERE ('" + NewsTag() + "' = t.Tag AND t.id = n.TagId AND a.id = n.NewsId) OR (n.TagId = 1 AND a.id = n.NewsId) order by itemdate desc " 
     SqlDataSource1.DataBind() 
    End Sub 
</script> 

<div class="halflist"> 
<asp:Repeater ID="Repeater2" runat="server" DataSourceID="SqlDataSource1"> 
    <ItemTemplate> 
     <div class="listitem"> 
      <h3> 
       <a href='<%# "/News/Article/" &Cstr(Eval("ID"))& "/" & helpers.urlSafe(Cstr(Eval("title")))%>'> 
        <asp:Label ID="Label4" runat="server" Text='<%# Eval("title") %>' /> 
       </a> 
      </h3> 
      <div class="thumbnail"> 
       <a href='<%# "/News/Article/" &Cstr(Eval("ID"))& "/" & helpers.urlSafe(Cstr(Eval("title")))%>'> 
        <Club:IThumb ID="ImageThumbnail2" runat="server" PhotoID='<%# Eval("photo") %>' /> 
       </a> 
      </div> 
      <asp:Label ID="Label3" class="liststamp" Font-Size="Smaller" runat="server" Text='<%# Eval("itemdate","{0:d}") %>' /> 
      <p> 
       <asp:Label ID="Label2" runat="server" Text='<%# helpers.CutIt(Convert.ToString(Eval("description")),150)%>' /> 
       <a class="readMore" href='<%# "/News/Article/" &Cstr(Eval("ID"))& "/" & helpers.urlSafe(Cstr(Eval("title")))%>'>read more &raquo;</a> 
      </p> 
      <div class="clearlist"> 
      </div> 
     </div> 
    </ItemTemplate> 
</asp:Repeater> 
</div> 
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ProviderName="System.Data.SqlClient" 
    ConnectionString="<%$ ConnectionStrings:ClubSiteDB %>" 

    SelectCommand="SELECT top @items a.[id], a.[itemdate], a.[title], a.[description], a.[photo] FROM [Announcements] a, [NewsInTags] n, [Tags] t WHERE (@tag = t.Tag AND t.id = n.TagId AND a.id = n.NewsId) OR (n.TagId = 1 AND a.id = n.NewsId) order by itemdate desc " 
    oninit="SqlDataSource1_Init"> 
       <SelectParameters> 
       <asp:Parameter Name="items" Type="Int16" DefaultValue="5" /> 
       <asp:Parameter Name="tag" Type="String" /> 
       </SelectParameters> 
       </asp:SqlDataSource> 

任何幫助將是巨大的，感謝

這裏

Answer 1

的問題是，您要訪問的視圖狀態（通過屬性）在init事件（數據源），它不適用，因此你的屬性將返回空字符串。

您可以在加載事件而不是init中更改您的select命令。請注意，您也可以使用Page_Load來修改您的數據源屬性。

還有一種方法是根據需要處理SqlDataSource.Selecting事件並根據事件參數修改Command對象（使用SqlDataSourceCommandEventArgs.Command訪問選擇事件處理器中的命令）。