Interestingly, you can also use the using/IDisposable pattern for other interesting things (such as the other point of the way that Rhino Mocks uses it). Basically, you can take advantage of the fact that the compiler will always call .Dispose on the "used" object. If you have something that needs to happen after a certain operation ... something that has a definite start and end ... then you can simply make an IDisposable class that starts the operation in the constructor, and then finishes in the Dispose method.

这允许您使用非常好的使用语法来指示所述操作的显式开始和结束。这也是系统如何。事务处理可以工作。

当使用ADO时。NET中，你可以在connection对象或reader对象上使用keywork。这样，当代码块完成时，它将自动处理您的连接。

当您希望在使用某个资源后将其销毁时，将使用Using。

例如，如果您分配了一个File资源，并且只需要在一段代码中使用它进行少量的读写，使用有助于在完成后立即处理File资源。

所使用的资源需要实现IDisposable才能正常工作。

例子:

using (File file = new File (parameters))
{
    // Code to do stuff with the file
}

using语句提供了一种方便的机制来正确使用IDisposable对象。作为规则，当您使用IDisposable对象时，您应该在using语句中声明并实例化它。

using语句以正确的方式调用对象上的Dispose方法，并且(如前面所示使用它时)它还会导致对象本身在调用Dispose时超出作用域。在using块中，对象是只读的，不能被修改或重新分配。

它来自这里。

在过去，我经常使用它来处理输入和输出流。您可以很好地嵌套它们，这消除了您通常遇到的许多潜在问题(通过自动调用dispose)。例如:

        using (FileStream fs = new FileStream("c:\file.txt", FileMode.Open))
        {
            using (BufferedStream bs = new BufferedStream(fs))
            {
                using (System.IO.StreamReader sr = new StreamReader(bs))
                {
                    string output = sr.ReadToEnd();
                }
            }
        }

Microsoft documentation states that using has a double function (https://msdn.microsoft.com/en-us/library/zhdeatwt.aspx), both as a directive and in statements. As a statement, as it was pointed out here in other answers, the keyword is basically syntactic sugar to determine a scope to dispose an IDisposable object. As a directive, it is routinely used to import namespaces and types. Also as a directive, you can create aliases for namespaces and types, as pointed out in the book "C# 5.0 In a Nutshell: The Definitive Guide" (http://www.amazon.com/5-0-Nutshell-The-Definitive-Reference-ebook/dp/B008E6I1K8), by Joseph and Ben Albahari. One example:

namespace HelloWorld
{
    using AppFunc = Func<IDictionary<DateTime, string>, List<string>>;
    public class Startup
    {
        public static AppFunc OrderEvents() 
        {
            AppFunc appFunc = (IDictionary<DateTime, string> events) =>
            {
                if ((events != null) && (events.Count > 0))
                {
                    List<string> result = events.OrderBy(ev => ev.Key)
                        .Select(ev => ev.Value)
                        .ToList();
                    return result;
                }
                throw new ArgumentException("Event dictionary is null or empty.");
            };
            return appFunc;
        }
    }
}

这是一种明智的做法，因为滥用这种做法会损害代码的清晰性。在DotNetPearls (http://www.dotnetperls.com/using-alias)中有一个关于c#别名的很好的解释，也提到了优点和缺点。