c# - 自定义 "using" block

Question

我正在使用一个数据库，并且有一种情况我想关闭其中的一个特性。关闭该功能看起来像这样......

DatabaseContext.Advanced.UseOptimisticConcurrency = false;

开启它同样简单。这功能很好。但我对某些东西很好奇，想探索它......

是否可以像处理 dispose 和 unsafe 那样将其包装在“using” block 中？例如……

using(DatabaseContext.Advanced.UseOptimisticConcurrency = false){
   // do things!
}

// the feature is turned back on automatically here!

更新

在 StackOverflow 的优秀人员的帮助下，我现在已经使我想要的行为完美运行。再次感谢。这是我的工作代码。不要介意冗长的文档。我只是那种把脑子里的所有东西都输入出来的程序员。

using System;

namespace Raven.Client {
    /// <summary>
    /// Used to emulate a series of transactions without optimistic concurrency in RavenDB
    /// </summary>
    /// <remarks>
    /// This has been flagged as an 'abuse' of the IDisposable interface, which is something I will learn more about
    /// and try to find a better solution. The purpose of this class is to make absolutely sure that we never use
    /// a document session without optimistic concurrency unless we are completely certain it is what we want. I
    /// elected to wrap this in a disposable block because that is an easy convention to remember, and it makes the
    /// intention very clear to the others who may see this code.
    /// Topics[0]: http://stackoverflow.com/questions/19643266/custom-using-blocks
    /// Topics[1]: http://stackoverflow.com/questions/2101524/is-it-abusive-to-use-idisposable-and-using-as-a-means-for-getting-scoped-beha/2103158#2103158
    /// Topics[2]: http://stackoverflow.com/questions/538060/proper-use-of-the-idisposable-interface
    /// </remarks>
    public class RavenPessimistic : IDisposable {
        private readonly IDocumentSession RavenSession;

        /// <summary>
        /// Disable optimistic concurrency for this exact session only.
        /// </summary>
        /// <param name="session"></param>
        public RavenPessimistic(IDocumentSession session) {
            RavenSession = session;
            RavenSession.Advanced.UseOptimisticConcurrency = false;
        }

        /// <summary>
        /// Enable the optimistic concurrency again, so that we do not
        /// ever use it unintentionally
        /// </summary>
        public void Dispose() {
            RavenSession.Advanced.UseOptimisticConcurrency = true;
        }
    }

    /// <summary>
    /// An extension method to make it more convenient to get to this. This is probably not necessary, but I have been
    /// anxious to see how RavenDB handles extension methods.
    /// </summary>
    public static class RavenSessionExtensions {
        public static RavenPessimistic OpenPessimisticSession(this IDocumentSession documentSession) {
            return new RavenPessimistic(documentSession);
        }
    }
}

然后，在我的实际代码中...

    /// <summary>
    /// Edit the given item prototype.
    /// </summary>
    /// <param name="model">
    /// A unique prototype to edit in the database.
    /// </param>
    /// <returns></returns>
    [HttpPost]
    [Route("items/edit/prototype")]
    public JsonResult Prototype(Models.Items.Prototype model) {
        if (ModelState.IsValid) {
            // go through the prototype and make sure to set all of the
            // mutation names to it.
            foreach (var mutation in model.Mutations) {
                mutation.Name = model.Name;
            }

            // we are updating an entry, instead of creating a new one,
            // so temporarily turn off optimistic concurrency since we
            // are 100% sure we want to overwrite the existing document.
            using (RavenSession.OpenPessimisticSession()) {
                RavenSession.Store(model);
                RavenSession.SaveChanges();
            }

            // if this was successful, then return the result to the client
            return Json(true, JsonRequestBehavior.AllowGet);
        }

        return Json(false, JsonRequestBehavior.AllowGet);
    }

Answer 1

只需将其包装在 IDisposable 类中，您就可以恢复 Dispose 函数中的功能。

public class SomeClass : IDisposable
{
     public SomeClass()
     {
          DatabaseContext.Advanced.UseOptimisticConcurrency = false;
     }

     public void Dispose()
     {
         DatabaseContext.Advanced.UseOptimisticConcurrency = true;
     }
}

以上代码只是示例，您需要根据自己的需要进行调整。