System.Web.Caching.DataCache下载System.Web.Caching.DataCache源代码下载

ASP.NET WebForms缓存非常方便地用于临时保留操作数据。在.NET平台的早期，即使在Winforms应用程序中，开发人员也经常使用System.Web名称空间。

关于ASP.NET缓存文章中不断提供的代码模板非常简单且实用：

 // 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缓存实现不包括一些理想的功能。

ASP.NET缓存设置

尽管在缓存中添加值的CACH.INSERT（字符串，对象）方法适用于大多数情况，但通常需要根据Web.config文件中存储的Web应用程序的设置为缓存数据进行不同的设置，有时甚至完全将缓存功能完全禁用于整个应用程序。在这种情况下，不应更改源代码，并且在不重新编译的情况下运行应用程序。

通用方法和默认值

无论该实例的实际类型是什么，ASP.NET缓存总是返回object类的实例。在大多数情况下，这不是问题，因为可以使用Nullable types代替Value types 。也许您想拥有从缓存中检索数据的通用方法：

 // 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" ) ;

如果不满足您的通用方法，则可以使用默认版本。实际上，这两个选择是相同的。但是通用方法提供了其他功能。例如，如果缓存不包含要检索的值，则可以定义默认值：

 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 */

深复制数据

ASP.NET缓存总是返回存储在缓存中的对象。这意味着更改提取的对象的任何属性也将更改存储在缓存中的对象，因为这些对象是相同的对象。在某些情况下，您可能需要修改检索到的对象，但将对象留在缓存中。方便的功能之一是从高速缓存中检索对象的副本，该副本可以更改，而不必担心缓存中的对象。

切奇数据区域

ASP.NET缓存类似于NameValueCollection 。对于小型Web应用程序来说，这是简单而优雅的解决方案，但是当应用程序长大时，很难生成钥匙。例如，考虑缓存两个相关表，例如供应商和模型。在这种情况下，Web应用程序将在一个缓存的对象中将所有数据保留在供应商表中，以及许多缓存对象，用于模型表的关联记录。供应商的钥匙应该是Vendors ，而应该是Models.[VendorID] 。当供应商表已更改后，供应商的缓存实例，仅需从缓存中删除模型的相关实例。这意味着应通过区域将数据缓存并从缓存中删除。

执行

所述功能是可选的，可以在任何Web应用程序中轻松实现。代理模板是实现所有描述的功能的好选择。所得的库可用于所有.NET框架，即启动版2.0。 .NET Framework 4.0介绍了System.Runtime.Caching名称空间和具有新的缓存模型的几个类。因此，不需要使用标准ASP.NET缓存及其改进。

悲伤但真实。

属性和设置

 /// <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 ;

枚举CacheExpirationType定义了如何将对象存储在缓存中

 /// <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
}

从缓存中提取数据的方法

 /// <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 ) )

将数据存储在缓存中的方法

 /// <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 )

从缓存中删除数据的方法

 /// <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。设置应用程序启动时默认参数

 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。在页面上或在DAL中实现使用CACHE的标准模板

 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
        }
    }
}

如果要定义与默认情况下指定的时间设置不同的时间设置，请使用覆盖的Insert{Which}Data方法之一。

3。在管理面板中或数据库更新时，还删除了键或以键的键或以键开头的键

 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
        }
    }
}