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如何编写会话扩展而不必为httpsessionstate和httpsessionstatebase编写单独的方法?

httpsession extension-methods asp.net-mvc

Byron Sommardahl · 技术社区 · 16 年前

我为会话编写了以下扩展方法,以便根据对象的类型来持久化和检索对象。这对我的解决方案很有效,但最终我不得不复制扩展方法来覆盖旧的httpsessionstate和新的httpsessionstatebase。我想找到一种方法,把这两种类型的照片还原成一组。有什么想法吗?

public static class SessionExtensions
{
    #region HttpSessionStateBase

    public static T Get<T>(this HttpSessionStateBase session)
    {
        return session.Get<T>(typeof(T).Name);
    }

    public static T Get<T>( this HttpSessionStateBase session, string key )
    {
        var obj = session[key];

        if( obj == null || typeof(T).IsAssignableFrom( obj.GetType() ) )
            return (T) obj;

        throw new Exception( "Type '" + typeof( T ).Name + "' doesn't match the type of the object retreived ('" + obj.GetType().Name + "')." );
    }

    public static void Put<T>(this HttpSessionStateBase session, T obj, string key)
    {
        session[key] = obj;
    }

    public static void Put<T>(this HttpSessionStateBase session, T obj)
    {
        session.Put(obj, typeof(T).Name);
    }

    #endregion

    #region HttpSessionState

    public static T Get<T>( this HttpSessionState session )
    {
        return session.Get<T>( typeof( T ).Name );
    }

    public static T Get<T>( this HttpSessionState session, string key )
    {
        var obj = session[ key ];

        if( obj == null || typeof( T ).IsAssignableFrom( obj.GetType() ) )
            return ( T ) obj;

        throw new Exception( "Type '" + typeof( T ).Name + "' doesn't match the type of the object retreived ('" + obj.GetType().Name + "')." );
    }

    public static void Put<T>( this HttpSessionState session, T obj )
    {
        session.Put( obj, typeof(T).Name );
    }

    public static void Put<T>( this HttpSessionState session, T obj, string key )
    {
        session[ key ] = obj;
    }

    #endregion
}

3 回复 | 直到 16 年前

Darin Dimitrov 16 年前

您可以保留最初的实现和使用 HttpSessionStateWrapper 处理 HttpSessionState 案例:

SomeType t = new HttpSessionStateWrapper(SomeHttpSessionStateInstance)
    .Get<SomeType>();

Byron Sommardahl 16 年前

我找到了一个可行的答案,但也有一些缺点。我希望有人能改进它。

@AndrewHare说,两者都不能实现公共基础或接口。嗯,事实上,他们有。它们都实现IEnumerable和ICollection。问题是,对于这两个信息,您想创建扩展方法来扩展实际上只用于会话的IEnumerable或ICollection吗?也许,也许不是。无论如何,这里有一种方法可以通过同时扩展httpsessionstate和httpsessionstatebase的扩展方法删除重复:

public static class SessionExtensions
{
    public static T Get<T>( this ICollection collection )
    {
        return collection.Get<T>( typeof( T ).Name );
    }

    public static T Get<T>( this ICollection collection, string key )
    {
        object obj = null;
        dynamic session = collection as HttpSessionState ?? ( dynamic ) ( collection as HttpSessionStateBase );

        if( session != null )
        {
            obj = session[key];

            if (obj != null && !typeof (T).IsAssignableFrom(obj.GetType()))
                throw new Exception("Type '" + typeof (T).Name + "' doesn't match the type of the object retreived ('" + obj.GetType().Name + "').");
        }

        return (T)obj;
    }

    public static void Put<T>( this ICollection collection, T obj )
    {
        collection.Put( obj, typeof( T ).Name );
    }

    public static void Put<T>( this ICollection collection, T obj, string key )
    {
        dynamic session = collection as HttpSessionState ?? ( dynamic ) ( collection as HttpSessionStateBase );
        if(session!=null)
            session[ key ] = obj;
    }
}

我对这个解决方案并不着迷,但至少在一个有趣的方向上,它感觉像是一个步骤。

Andrew Hare 16 年前

不幸的是,这两种类型都没有您可以使用的公共基类或接口——目前,您必须复制扩展方法。