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Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here.

WebPart.PartCacheRead Method

Windows SharePoint Services 3

Reads and returns a value from the specified location in the specified type of storage in the Web Part cache.

Namespace:  Microsoft.SharePoint.WebPartPages
Assembly:  Microsoft.SharePoint (in Microsoft.SharePoint.dll)

protected Object PartCacheRead(
	Storage storage,
	string key
)

Parameters

storage
Type: Microsoft.SharePoint.WebPartPages.Storage
A Storage value that specifies the type of storage in the Web Part cache where a value is read. Possible values are Personal and Shared. Specifying None returns a null reference (Nothing in Visual Basic).
key
Type: System.String
The name of the value to be read from the Web Part cache.

Return Value

Type: System.Object
An object that returns the value that is read.

The following code example shows a Web Part that caches and displays the time when it is first rendered, and provides a button to refresh the Web Part cache with the current time.

using System;
using System.ComponentModel;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Xml.Serialization;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Utilities;
using Microsoft.SharePoint.WebPartPages;

namespace WebPartLibrary1
{
    /// <summary>
    /// Summary description for CacheSample.
    /// </summary>
    [DefaultProperty("Text"),
        ToolboxData("<{0}:CacheSample runat=server></{0}:CacheSample>"),
        XmlRoot(Namespace="WebPartLibrary1")]

    public class CacheSample : Microsoft.SharePoint.WebPartPages.WebPart
    {
        Button refreshButton;

        public CacheSample()
        {
            this.PreRender+=new EventHandler(UpdateCache);
        }

        protected override void CreateChildControls()
        {
            refreshButton = new Button();
            refreshButton.Text="Refresh Cache";
            refreshButton.Click+=new EventHandler(refreshButton_click);
            this.Controls.Add(refreshButton);
        }

        public void UpdateCache(object o, System.EventArgs e)
        {

            if(this.PartCacheRead(Storage.Shared,"cacheKey") == null)
            {
                this.PartCacheWrite(Storage.Shared,"cacheKey", fetchData(), TimeSpan.FromSeconds(10));
            }
        }

        private void refreshButton_click(object o, System.EventArgs e)
        {
            this.PartCacheInvalidate(Storage.Shared, "cacheKey");
        }

        protected override void RenderWebPart(HtmlTextWriter output)
        {
            output.Write("Cache Value: ");
            output.Write(PartCacheRead(Storage.Shared,"cacheKey")+ "&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;");
            this.RenderChildren(output);
        }

        private string fetchData()
        {
            return DateTime.Now.ToLongTimeString();
        }
    }
}

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