C #에서 폐기 된 폐쇄에 대한 액세스?

C #에서 폐기 된 폐쇄에 대한 액세스?

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Microsoft 엔터프라이즈 라이브러리 (데이터 응용 프로그램 블록)를 조사하고 있습니다. 샘플 sln.

그들은 비동기 적으로 데이터를 읽는 샘플을 가지고 있습니다 ( IAsync새로운 버전 (6)도 지원하지만 async).

하지만 Resharper ( 또는 Visual Studio- nevermind )는 다음과 같이 표시합니다. "처분 된 폐쇄에 대한 액세스": (먼저 이미지를 표시 할 것이므로 더 명확해질 것입니다. 그런 다음 코드를 붙여 넣습니다)

코드 :

/*1*/    [Description("Execute a command that retrieves data asynchronously")]
/*2*/    static void ReadDataAsynchronously()
/*3*/    {
/*4*/        if (!SupportsAsync(asyncDB)) return;
/*5*/   
/*6*/        using(var doneWaitingEvent = new ManualResetEvent(false))
/*7*/        using(var readCompleteEvent = new ManualResetEvent(false))
/*8*/        {
/*9*/            try
/*10*/            {
/*11*/                // Create command to execute stored procedure and add parameters
/*12*/                DbCommand cmd = asyncDB.GetStoredProcCommand("ListOrdersSlowly");
/*13*/                asyncDB.AddInParameter(cmd, "state", DbType.String, "Colorado");
/*14*/                asyncDB.AddInParameter(cmd, "status", DbType.String, "DRAFT");
/*15*/                // Execute the query asynchronously specifying the command and the
/*16*/                // expression to execute when the data access process completes.
/*17*/                asyncDB.BeginExecuteReader(cmd,
/*18*/                    asyncResult = >
/*19*/                    {
/*20*/                        // Lambda expression executed when the data access completes.
/*21*/                        doneWaitingEvent.Set();
/*22*/                        try
/*23*/                        {
/*24*/                            using(IDataReader reader = asyncDB.EndExecuteReader(asyncResult))
/*25*/                            {
/*26*/                                Console.WriteLine();
/*27*/                                Console.WriteLine();
/*28*/                                DisplayRowValues(reader);
/*29*/                            }
/*30*/                        }
/*31*/                        catch (Exception ex)
/*32*/                        {
/*33*/                            Console.WriteLine("Error after data access completed: {0}", ex.Message);
/*34*/                        }
/*35*/                        finally
/*36*/                        {
/*37*/                            readCompleteEvent.Set();
/*38*/                        }
/*39*/                    }, null);
/*40*/   
/*41*/                // Display waiting messages to indicate executing asynchronouly
/*42*/                while (!doneWaitingEvent.WaitOne(1000))
/*43*/                {
/*44*/                    Console.Write("Waiting... ");
/*45*/                }
/*46*/   
/*47*/                // Allow async thread to write results before displaying "continue" prompt
/*48*/                readCompleteEvent.WaitOne();
/*49*/            }
/*50*/            catch (Exception ex)
/*51*/            {
/*52*/                Console.WriteLine("Error while starting data access: {0}", ex.Message);
/*53*/            }
/*54*/        }
/*55*/    }

질문 :

이 경고를하는 이유는 무엇입니까? 없다 manualreset-checked-signal(루프에서 실행되는)되는 것을 방지using 하는 방법을 - - 절에 도달 할 수 없음을 dispose호출합니다.

그렇다면 왜 소리를 지르나요 (경고)?

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You pass doneWaitingEvent to a lambda that may extend beyond the scope of the using block. I.e. there's a risk that Dispose will have been called when the lambda executes.

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It yells warning because the engine is not smart enough to figure out that the using block will never be exited before the delegate code completes. That is why this is a warning not a error.

You can safely ignore this warning, you can have resharper suppress the warning by wrapping the lines with special comments

asyncDB.BeginExecuteReader(cmd, asyncResult =>
{
    // Lambda expression executed when the data access completes.
    // ReSharper disable AccessToDisposedClosure
    doneWaitingEvent.Set();
    // ReSharper restore AccessToDisposedClosure
    try
    {
        using (IDataReader reader = asyncDB.EndExecuteReader(asyncResult))
        {
            Console.WriteLine();
            Console.WriteLine();
            DisplayRowValues(reader);
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine("Error after data access completed: {0}", ex.Message);
    }
    finally
    {
        // ReSharper disable AccessToDisposedClosure
        readCompleteEvent.Set();
        // ReSharper restore AccessToDisposedClosure
    }
}, null);

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The reason you see ReSharper's warnings is that ReSharper's code flow analysis engine is not strong enough to see what is going on: they assume that your code could get to the end of the using clause without doneWaitingEvent being set, which is not possible due to a while loop:

while (!doneWaitingEvent.WaitOne(1000)) {
    Console.Write("Waiting... ");
}

루프는 호출 "Waiting... "될 때까지 라인 을 계속 인쇄 doneWaitingEvent.Set();하여 코드가 using블록 끝에 도달하지 못하도록합니다 . 다른 경고도 마찬가지입니다.

간단히 말해서이 경고는 무시해도됩니다. ReSharper의 "이 경고 무시"주석을 추가하고 선택적으로 버그 보고서를 제출합니다.

참고 URL : https://stackoverflow.com/questions/17620430/access-to-disposed-closure-in-c