HttpResponse.AddCacheItemDependency(String) 方法

定義

命名空間:

System.Web

組件:

System.Web.dll

這使得快取回應的有效性依賴於快取中的另一個項目。

public:
 void AddCacheItemDependency(System::String ^ cacheKey);

public void AddCacheItemDependency(string cacheKey);

member this.AddCacheItemDependency : string -> unit

Public Sub AddCacheItemDependency (cacheKey As String)

參數

cacheKey

String

快取回應所依賴的項目的鍵值。

範例

以下範例是一個 ASP.NET 的使用者控制項，輸出快取。 控制項的程式碼會呼叫 AddCacheItemDependency 該方法，並以物件中儲存 Cache 的項目的鍵值作為參數傳遞。 若該項目不存在於快取中，則儲存在輸出快取中的控制項回應將失效。 這表示在後續請求時，控制項回應的新版本會被加入輸出快取。

接著，程式碼檢查物件 bookData 中是否儲存 Cache 與鍵相關的項目，並顯示兩行文字中的一行，取決於結果。 接著，程式碼會以呼叫自訂DataHelper類別的共享GetBookData方法，設定DataGridDataSource一個名為 dgBooks的控制項屬性，並將該方法填充DataGridDataBind。

    <%@ Control Language="c#" %>
    <%@ Outputcache duration="10" varybyparam="none" shared="True" %>
    <%@ Import Namespace = "Samples.AspNet.CS" %>
    <%@ Import Namespace = "System.Data" %>

<script runat="server">

    private void Page_Load(object sender, System.EventArgs e)
    {
    
        // Make user control invalid if the
        // cache item changes or expires.
        Response.AddCacheItemDependency("bookData");

        // Create a DataView object.
        DataView source = (DataView)Cache["bookData"];
    
        // Check if the view is stored in the cache
        // and generate the right label text
        // dependent upon what is returned.
        if (source == null)
        {
            source = DataHelper.GetBookData();
            lblCacheMsg.Text = "Data generated explicitly.";
        }
        else
        {
            lblCacheMsg.Text = "Data retrieved from application cache.";
        }
    
        dgBooks.DataSource = source;
        dgBooks.DataBind();
    
        lblOutputMessage.Text = DateTime.Now.ToString();
    }

</script>
    <table>
        <tbody>
            <tr>
                <th>
                    Books</th>
                <td>
                </td>
            </tr>
            <tr>
                <td>
                    <asp:DataGrid id="dgBooks" runat="server"></asp:DataGrid>
                </td>
                <td>
                </td>
            </tr>
            <tr>
                <td>
                    <asp:Label id="lblCacheMsg" runat="server"></asp:Label>
                </td>
                <td>
                </td>
            </tr>
            <tr>
                <td>
                    The control was created at: 
                </td>
                <td>
                    <asp:Label id="lblOutputMessage" runat="server"></asp:Label>
                </td>
            </tr>
        </tbody>
    </table>

<%@ Control Language="vb" %>
<%@ Outputcache duration="10" varybyparam="none" shared="True" %>
<%@ Import Namespace="Samples.AspNet.VB" %>
<%@ Import Namespace="System.Data" %>
<script runat="server">

    Private Sub Page_Load(sender As Object, e As System.EventArgs)
    
        ' Make user control invalid if the 
        ' cache item changes or expires.
        Response.AddCacheItemDependency("bookData")


        ' Create a DataView object.
        Dim source As DataView = Cache("bookData")
    
        ' Check if the view is stored in the cache
        ' and generate the right label text
        ' dependent upon what is returned.
        If source Is Nothing Then

           source = DataHelper.GetBookData()
           lblCacheMsg.Text = "Data generated explicitly."
        Else
           lblCacheMsg.Text = "Data retrieved from application cache."
        End If
    
        dgBooks.DataSource = source
        dgBooks.DataBind()
    
        lblOutputMessage.Text = DateTime.Now.ToString()
    End Sub

</script>

    <table>
        <tbody>
            <tr>
                <th>
                    Books</th>
                <td>
                </td>
            </tr>
            <tr>
                <td>
                    <asp:DataGrid id="dgBooks" runat="server"></asp:DataGrid>
                </td>
                <td>
                </td>
            </tr>
            <tr>
                <td>
                    <asp:Label id="lblCacheMsg" runat="server"></asp:Label>
                </td>
                <td>
                </td>
            </tr>
            <tr>
                <td>
                    The control was created at: 
                </td>
                <td>
                    <asp:Label id="lblOutputMessage" runat="server"></asp:Label>
                </td>
            </tr>
        </tbody>
    </table>
     

備註

當對應 cacheKey 參數的項目從快取中移除時，目前快取項目的回應即無效。

另請參閱

• AddCacheItemDependency(String)
• 快取 ASP.NET 頁面