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SuperSocket的Command Filter功能类似于ASP.NET MVC中的Action Filter，你可以用它来截获Command的执行，在Command运行之前或之后运行Filter的代码。

Command Filter必须继承自Attribute类CommandFilterAttribute：

[AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]

public abstract class CommandFilterAttribute : Attribute

{

    public abstract void OnCommandExecuting(IAppSession session, ICommand command);

    public abstract void OnCommandExecuted(IAppSession session, ICommand command);

}

你的CommandFilter有两个方法需要实现，

OnCommandExecuting: 此方法在Command执行之前被调用；

OnCommandExecuted: 此方法在Command执行之后被调用；

下面的代码定义了LogTimeCommandFilterAttribute这一Command Filter用于记录执行时间超过5秒的Command, 并通过Attribute的方式应用于QUERY这一Command:

public class LogTimeCommandFilterAttribute : CommandFilterAttribute

{

    public override void OnCommandExecuting(IAppSession session, ICommand command)

    {

        session.Items["StartTime"] = DateTime.Now;

    }

    public override void OnCommandExecuted(IAppSession session, ICommand command)

    {

        var startTime = session.Items.GetValue<DateTime>("StartTime");

        var ts = DateTime.Now.Subtract(startTime);

        if (ts.TotalSeconds > 5)

        {

            session.Logger.LogPerf(string.Format("A command '{0}' took {1} seconds!", command.Name, ts.ToString()));

        }

    }

}

[LogTimeCommandFilter]

public class QUERY : StringCommandBase<TestSession>

{

    public override void ExecuteCommand(TestSession session, StringCommandInfo commandData)

    {

        //Your code

    }

}

如果你想把某个Command Filter应用于所有的Command, 你只需将Command Filter的Attribute加到你的              AppServer类上面，如下代码:

[LogTimeCommandFilter]

public class TestServer : AppServer<TestSession>

{

    public TestServer()

        : base()

    {

    }

}