System.Web.Caching.DataCache下載System.Web.Caching.DataCache源代碼下載

ASP.NET WebForms緩存非常方便地用於臨時保留操作數據。在.NET平台的早期，即使在Winforms應用程序中，開發人員也經常使用System.Web名稱空間。

關於ASP.NET緩存文章中不斷提供的代碼模板非常簡單且實用：

 // try to get an instance of object from cache
DataSet ds = HttpRuntime . Cache [ "KeyName" ] as DataSet ;
// check the result and recreate it, if it is null
if ( ds == null )
{
    ds = QueryDataFromDatabase ( ) ;
    HttpRuntime . Cache . Insert ( "KeyName" , ds ) ;
}
// using the instance of object that has been populated from cache or from storage
DataRow dr = ds . Tables [ 0 ] . Rows [ 0 ] ;

但是，ASP.NET緩存實現不包括一些理想的功能。

ASP.NET緩存設置

儘管在緩存中添加值的CACH.INSERT（字符串，對象）方法適用於大多數情況，但通常需要根據Web.config文件中存儲的Web應用程序的設置為緩存數據進行不同的設置，有時甚至完全將緩存功能完全禁用於整個應用程序。在這種情況下，不應更改源代碼，並且在不重新編譯的情況下運行應用程序。

通用方法和默認值

無論該實例的實際類型是什麼，ASP.NET緩存總是返回object類的實例。在大多數情況下，這不是問題，因為可以使用Nullable types代替Value types 。也許您想擁有從緩存中檢索數據的通用方法：

 // this is a dafault extraction data from cache
myClassName item = HttpRuntime . Cache [ "Key1" ] as myClassName ; 

// this is a desired extraction data with generic methods
myClassName item = DataCache . Get < myClassName > ( "Key1" ) ;

如果不滿足您的通用方法，則可以使用默認版本。實際上，這兩個選擇是相同的。但是通用方法提供了其他功能。例如，如果緩存不包含要檢索的值，則可以定義默認值：

 myClassName defaultValue = new myClassName ( /* init properties */ ) ;
myClassName item = DataCache . Get < myClassName > ( "Key1" , defaultValue ) ; 
/* if there is nothing in the cache, then the item will be defaultValue */

深複製數據

ASP.NET緩存總是返回存儲在緩存中的對象。這意味著更改提取的對象的任何屬性也將更改存儲在緩存中的對象，因為這些對像是相同的對象。在某些情況下，您可能需要修改檢索到的對象，但將對象留在緩存中。方便的功能之一是從高速緩存中檢索對象的副本，該副本可以更改，而不必擔心緩存中的對象。

切奇數據區域

ASP.NET緩存類似於NameValueCollection 。對於小型Web應用程序來說，這是簡單而優雅的解決方案，但是當應用程序長大時，很難生成鑰匙。例如，考慮緩存兩個相關表，例如供應商和模型。在這種情況下，Web應用程序將在一個緩存的對像中將所有數據保留在供應商表中，以及許多緩存對象，用於模型表的關聯記錄。供應商的鑰匙應該是Vendors ，而應該是Models.[VendorID] 。當供應商表已更改後，供應商的緩存實例，僅需從緩存中刪除模型的相關實例。這意味著應通過區域將數據緩存並從緩存中刪除。

執行

所述功能是可選的，可以在任何Web應用程序中輕鬆實現。代理模板是實現所有描述的功能的好選擇。所得的庫可用於所有.NET框架，即啟動版2.0。 .NET Framework 4.0介紹了System.Runtime.Caching名稱空間和具有新的緩存模型的幾個類。因此，不需要使用標準ASP.NET緩存及其改進。

悲傷但真實。

屬性和設置

 /// <summary>
/// Is cache used or not
/// </summary>
public static bool IsCacheEnable ;

/// <summary>
/// How to store objects in the cache
/// </summary>
public static CacheExpirationType ExpirationType ;

/// <summary>
/// How long objects should be stored in the cache 
/// </summary>
public static TimeSpan ExpirationTime ;

枚舉CacheExpirationType定義瞭如何將對象存儲在緩存中

 /// <summary>
/// How to store objects in the cache
/// </summary>
public enum CacheExpirationType
{
    /// <summary>
    /// Without time limit, the value of the <seealso cref = "DataCache.ExpirationTime" /> property will be ignored
    /// </summary>
    NoExpiration ,

    /// <summary>
    /// The <seealso cref="DataCache.ExpirationTime"/> at which the inserted object expires and is removed from the cache
    /// </summary>
    AbsoluteExpiration ,

    /// <summary>
    /// The interval <seealso cref="DataCache.ExpirationTime"/> between the time the inserted object is last accessed and the time at which that object expires
    /// </summary>
    SlidingExpiration
}

從緩存中提取數據的方法

 /// <summary>
/// Retrieves the specified item from the Cache object
/// </summary>
/// <typeparam name="T">The type for the cache item to retrieve</typeparam>
/// <param name="key">The identifier for the cache item to retrieve</param>
/// <param name="defaultValue">The default value if the object is not in the cache</param>
/// <returns>The retrieved cache item, or <paramref name="defaultValue"/> if the key is not found</returns>
public static T GetData < T > ( string key , T defaultValue = default ( T ) )

/// <summary>
/// Retrieves the deep copied of specified item from the Cache object
/// </summary>
/// <typeparam name="T">The type for the cache item to retrieve</typeparam>
/// <param name="key">The identifier for the cache item to retrieve</param>
/// <param name="defaultValue">The default value if the object is not in the cache</param>
/// <returns>The retrieved cache item, or <paramref name="defaultValue"/> if the key is not found</returns>
public static T GetDeepCopiedData < T > ( string key , T defaultValue = default ( T ) )

將數據存儲在緩存中的方法

 /// <summary>
/// Inserts an item into the cache with a cache key to reference its location, using default values provided by the settings
/// </summary>
/// <param name="key">The cache key used to reference the item</param>
/// <param name="value">The object to be inserted into the cache</param>
public static void InsertData ( string key , object value )

/// <summary>
/// Inserts an item into the cache with a cache key to reference its location, using the absolute expiration time
/// </summary>
/// <param name="key">The cache key used to reference the item</param>
/// <param name="value">The object to be inserted into the cache</param>
/// <param name="expirationTime">How long the object should be stored in the cache</param>
public static void InsertAbsoluteExpirationData ( string key , object value , TimeSpan expirationTime )

/// <summary>
/// Inserts an item into the cache with a cache key to reference its location, using the sliding expiration time
/// </summary>
/// <param name="key">The cache key used to reference the item</param>
/// <param name="value">The object to be inserted into the cache</param>
/// <param name="expirationTime">How long the object should be stored in the cache</param>
public static void InsertSlidingExpirationData ( string key , object value , TimeSpan expirationTime )

/// <summary>
/// Inserts an item into the cache with a cache key to reference its location, using the type of expiration and default value for expiration time
/// </summary>
/// <param name="key">The cache key used to reference the item</param>
/// <param name="value">The object to be inserted into the cache</param>
/// <param name="expirationType">How to store objects in the cache</param>
public static void InsertExpirationData ( string key , object value , CacheExpirationType expirationType )

/// <summary>
/// Inserts an item into the cache with a cache key to reference its location, using the type of expiration and expiration time
/// </summary>
/// <param name="key">The cache key used to reference the item</param>
/// <param name="value">The object to be inserted into the cache</param>
/// <param name="expirationType">How to store objects in the cache</param>
/// <param name="expirationTime">How long the object should be stored in the cache</param>
public static void InsertExpirationData ( string key , object value , CacheExpirationType expirationType , TimeSpan expirationTime )

從緩存中刪除數據的方法

 /// <summary>
/// Removes the specified item from the application's cache 
/// </summary>
/// <param name="key">An identifier for the cache item to remove</param>
public static void RemoveDataByKey ( string key )

/// <summary>
/// Removes all items from the application's cache that starts with key
/// </summary>
/// <param name="keyStartsWith">An starts with identifier for the cache item to remove</param>
public static void RemoveAllDataByKey ( string keyStartsWith )

/// <summary>
/// Removes all items from the application's cache 
/// </summary>
public static void RemoveAllData ( )

用法示例

1。設置應用程序啟動時默認參數

 public class Global : System . Web . HttpApplication
{
    protected void Application_Start ( object sender , EventArgs e )
    {
        Settings settings = Settings . Default ;
        DataCache . IsCacheEnable = settings . IsCacheEnable ;
        DataCache . ExpirationType = settings . ExpirationType ;
        DataCache . ExpirationTime = settings . ExpirationTime ;
    }
}

2。在頁面上或在DAL中實現使用CACHE的標準模板

 public partial class DefaultPage : System . Web . UI . Page
{
    public const string STR_CACHENAME = "something" ;

    protected void Page_Load ( object sender , EventArgs e )
    {
        if ( ! this . IsPostBack )
        {
            SomethingDataModel val = DataCache . GetData < SomethingDataModel > ( STR_CACHENAME ) ;
            if ( val == null ) 
            {
                SomethingDataModel val = new SomethingDataModel ( ) ; // get data from ...
                DataCache . InsertData ( STR_CACHENAME , val ) ;
            }
            DataBind ( val ) ; // use data on the page
        }
    }
}

如果要定義與默認情況下指定的時間設置不同的時間設置，請使用覆蓋的Insert{Which}Data方法之一。

3。在管理面板中或數據庫更新時，還刪除了鍵或以鍵的鍵或以鍵開頭的鍵

 public partial class DefaultPage : System . Web . UI . Page
{
    public const string STR_CACHENAME = "something" ;

    protected void Page_Load ( object sender , EventArgs e )
    {
        if ( this . IsPostBack )
        {
            DAL . Update ( ) ; // update the database ...
            DataCache . RemoveAllDataByKey ( STR_CACHENAME ) ; // clear cache
            Response . Redirect ( "Default.aspx" ) ; // proccessing the request
        }
    }
}