SqlClient 스트리밍 지원SqlClient Streaming Support

SQL Server와 응용 프로그램 간의 스트리밍 지원 (.NET Framework 4.5의 새로운 기능)은 서버 (문서, 이미지 및 미디어 파일)에서 구조화 되지 않은 데이터를 지원 합니다.Streaming support between SQL Server and an application (new in .NET Framework 4.5) supports unstructured data on the server (documents, images, and media files). SQL Server 데이터베이스는 Blob (binary large object)를 저장할 수 있지만 BLOB 검색은 많은 메모리를 사용할 수 있습니다.A SQL Server database can store binary large objects (BLOBs), but retrieving BLOBS can use a lot of memory.

SQL Server에 대 한 스트리밍 지원을 통해 데이터를 메모리에 완전히 로드 하지 않고도 데이터를 스트리밍하는 응용 프로그램을 쉽게 작성할 수 있으므로 메모리 오버플로 예외가 줄어듭니다.Streaming support to and from SQL Server simplifies writing applications that stream data, without having to fully load the data into memory, resulting in fewer memory overflow exceptions.

또한 스트리밍 지원을 통해 중간 계층 애플리케이션의 확장성이 높아질 수 있습니다. 특히 대형 BLOB를 전송, 검색 및 조작하기 위해 비즈니스 개체를 SQL Azure에 연결하는 시나리오에서는 더욱 그렇습니다.Streaming support will also enable middle-tier applications to scale better, especially in scenarios where business objects connect to SQL Azure in order to send, retrieve, and manipulate large BLOBs.

경고

응용 프로그램에서 Context Connection 연결 문자열 키워드도 사용하는 경우에는 비동기 호출이 지원되지 않습니다.Asynchronous calls are not supported if an application also uses the Context Connection connection string keyword.

스트리밍을 지원하기 위해 추가된 멤버는 쿼리에서 데이터를 검색하고 쿼리 및 저장 프로시저에 매개 변수를 전달하는 데 사용됩니다.The members added to support streaming are used to retrieve data from queries and to pass parameters to queries and stored procedures. 스트리밍 기능은 기본 OLTP 및 데이터 마이그레이션 시나리오를 처리하며 온-프레미스 및 오프-프레미스 데이터 마이그레이션 환경에 적용할 수 있습니다.The streaming feature addresses basic OLTP and data migration scenarios and is applicable to on premise and off premise data migrations.environments.

SQL Server에서의 스트리밍 지원Streaming Support from SQL Server

SQL Server에서의 스트리밍 지원은, 및 DbDataReader Stream SqlDataReader XmlReader 개체TextReader 를 가져오고이에 대응할 수 있도록 클래스에서 및의 새로운 기능을 소개 합니다.Streaming support from SQL Server introduces new functionality in the DbDataReader and in the SqlDataReader classes in order to get Stream, XmlReader, and TextReader objects and react to them. 이러한 클래스는 쿼리에서 데이터를 검색하는 데 사용됩니다.These classes are used to retrieve data from queries. 따라서 SQL Server에서의 스트리밍 지원은 OLTP 시나리오를 해결 하 고 온-프레미스 및 오프-프레미스 환경에 적용 됩니다.As a result, Streaming support from SQL Server addresses OLTP scenarios and applies to on-premise and off-premise environments.

SQL Server에서의 스트리밍 지원을 사용 SqlDataReader 하기 위해에 추가 된 멤버는 다음과 같습니다.The following members were added to SqlDataReader to enable streaming support from SQL Server:

  1. IsDBNullAsync

  2. SqlDataReader.GetFieldValue

  3. GetFieldValueAsync

  4. GetStream

  5. GetTextReader

  6. GetXmlReader

SQL Server에서의 스트리밍 지원을 사용 DbDataReader 하기 위해에 추가 된 멤버는 다음과 같습니다.The following members were added to DbDataReader to enable streaming support from SQL Server:

  1. GetFieldValue

  2. GetStream

  3. GetTextReader

SQL Server에 대 한 스트리밍 지원Streaming Support to SQL Server

SQL Server에 SqlParameter 대 한 스트리밍 지원은 XmlReader, StreamTextReader 개체를 허용 하 고 대응할 수 있도록 클래스의 새 기능을 도입 합니다.Streaming support to SQL Server introduces new functionality in the SqlParameter class so it can accept and react to XmlReader, Stream, and TextReader objects. SqlParameter는 쿼리 및 저장 프로시저에 매개 변수를 전달하는 데 사용됩니다.SqlParameter is used to pass parameters to queries and stored procedures.

SqlCommand 개체를 삭제하거나 Cancel을 호출할 때는 모든 스트리밍 작업이 취소되어야 합니다.Disposing a SqlCommand object or calling Cancel must cancel any streaming operation. 애플리케이션에서 CancellationToken을 전송하면 취소되지 않을 수 있습니다.If an application sends CancellationToken, cancellation is not guaranteed.

다음 SqlDbType 형식에서는 ValueStream를 받아들입니다.The following SqlDbType types will accept a Value of Stream:

  • 이진Binary

  • VarBinaryVarBinary

다음 SqlDbType 형식에서는 ValueTextReader를 받아들입니다.The following SqlDbType types will accept a Value of TextReader:

  • CharChar

  • NCharNChar

  • NVarCharNVarChar

  • XmlXml

Value Xml SqlDbType 형식은 의XmlReader를 허용 합니다.The XmlSqlDbType type will accept a Value of XmlReader.

SqlValueXmlReader, TextReaderStream 형식의 값만 받아들일 수 있습니다.SqlValue can accept values of type XmlReader, TextReader, and Stream.

XmlReader, TextReaderStream 개체는 Size에 정의된 값까지 전송됩니다.The XmlReader, TextReader, and Stream object will be transferred up to the value defined by the Size.

샘플-SQL Server에서 스트리밍Sample -- Streaming from SQL Server

다음 Transact-sql을 사용 하 여 예제 데이터베이스를 만듭니다.Use the following Transact-SQL to create the sample database:

CREATE DATABASE [Demo]
GO
USE [Demo]
GO
CREATE TABLE [Streams] (
[id] INT PRIMARY KEY IDENTITY(1, 1),
[textdata] NVARCHAR(MAX),
[bindata] VARBINARY(MAX),
[xmldata] XML)
GO
INSERT INTO [Streams] (textdata, bindata, xmldata) VALUES (N'This is a test', 0x48656C6C6F, N'<test>value</test>')
INSERT INTO [Streams] (textdata, bindata, xmldata) VALUES (N'Hello, World!', 0x54657374696E67, N'<test>value2</test>')
INSERT INTO [Streams] (textdata, bindata, xmldata) VALUES (N'Another row', 0x666F6F626172, N'<fff>bbb</fff><fff>bbc</fff>')
GO

이 샘플에서는 다음 작업의 수행 방법을 보여 줍니다.The sample shows how to do the following:

  • 큰 파일을 검색하는 비동기적 방법을 제공하여 사용자 인터페이스 스레드의 차단을 방지합니다.Avoid blocking a user-interface thread by providing an asynchronous way to retrieve large files.

  • .NET Framework 4.5의 SQL Server에서 많은 텍스트 파일을 전송 합니다.Transfer a large text file from SQL Server in .NET Framework 4.5.

  • SQL Server에서 .NET Framework 4.5의 대량 XML 파일을 전송 합니다.Transfer a large XML file from SQL Server in .NET Framework 4.5.

  • SQL Server에서 데이터를 검색 합니다.Retrieve data from SQL Server.

  • 메모리가 부족 하지 않고 SQL Server 데이터베이스 간에 대량 파일 (Blob)을 전송 합니다.Transfer large files (BLOBs) from one SQL Server database to another without running out of memory.

using System;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Threading.Tasks;
using System.Xml;

namespace StreamingFromServer {
   class Program {
      // Replace the connection string if needed, for instance to connect to SQL Express: @"Server=(local)\SQLEXPRESS;Database=Demo;Integrated Security=true"
      private const string connectionString = @"Server=(localdb)\V11.0;Database=Demo";

      static void Main(string[] args) {
         CopyBinaryValueToFile().Wait();
         PrintTextValues().Wait();
         PrintXmlValues().Wait();
         PrintXmlValuesViaNVarChar().Wait();

         Console.WriteLine("Done");
      }

      // Application retrieving a large BLOB from SQL Server in .NET 4.5 using the new asynchronous capability
      private static async Task CopyBinaryValueToFile() {
         string filePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "binarydata.bin");

         using (SqlConnection connection = new SqlConnection(connectionString)) {
            await connection.OpenAsync();
            using (SqlCommand command = new SqlCommand("SELECT [bindata] FROM [Streams] WHERE [id]=@id", connection)) {
               command.Parameters.AddWithValue("id", 1);

               // The reader needs to be executed with the SequentialAccess behavior to enable network streaming
               // Otherwise ReadAsync will buffer the entire BLOB into memory which can cause scalability issues or even OutOfMemoryExceptions
               using (SqlDataReader reader = await command.ExecuteReaderAsync(CommandBehavior.SequentialAccess)) {
                  if (await reader.ReadAsync()) {
                     if (!(await reader.IsDBNullAsync(0))) {
                        using (FileStream file = new FileStream(filePath, FileMode.Create, FileAccess.Write)) {
                           using (Stream data = reader.GetStream(0)) {

                              // Asynchronously copy the stream from the server to the file we just created
                              await data.CopyToAsync(file);
                           }
                        }
                     }
                  }
               }
            }
         }
      }

      // Application transferring a large Text File from SQL Server in .NET 4.5
      private static async Task PrintTextValues() {
         using (SqlConnection connection = new SqlConnection(connectionString)) {
            await connection.OpenAsync();
            using (SqlCommand command = new SqlCommand("SELECT [id], [textdata] FROM [Streams]", connection)) {

               // The reader needs to be executed with the SequentialAccess behavior to enable network streaming
               // Otherwise ReadAsync will buffer the entire text document into memory which can cause scalability issues or even OutOfMemoryExceptions
               using (SqlDataReader reader = await command.ExecuteReaderAsync(CommandBehavior.SequentialAccess)) {
                  while (await reader.ReadAsync()) {
                     Console.Write("{0}: ", reader.GetInt32(0));

                     if (await reader.IsDBNullAsync(1)) {
                        Console.Write("(NULL)");
                     }
                     else {
                        char[] buffer = new char[4096];
                        int charsRead = 0;
                        using (TextReader data = reader.GetTextReader(1)) {
                           do {
                              // Grab each chunk of text and write it to the console
                              // If you are writing to a TextWriter you should use WriteAsync or WriteLineAsync
                              charsRead = await data.ReadAsync(buffer, 0, buffer.Length);
                              Console.Write(buffer, 0, charsRead);
                           } while (charsRead > 0);
                        }
                     }

                     Console.WriteLine();
                  }
               }
            }
         }
      }

      // Application transferring a large Xml Document from SQL Server in .NET 4.5
      private static async Task PrintXmlValues() {
         using (SqlConnection connection = new SqlConnection(connectionString)) {
            await connection.OpenAsync();
            using (SqlCommand command = new SqlCommand("SELECT [id], [xmldata] FROM [Streams]", connection)) {

               // The reader needs to be executed with the SequentialAccess behavior to enable network streaming
               // Otherwise ReadAsync will buffer the entire Xml Document into memory which can cause scalability issues or even OutOfMemoryExceptions
               using (SqlDataReader reader = await command.ExecuteReaderAsync(CommandBehavior.SequentialAccess)) {
                  while (await reader.ReadAsync()) {
                     Console.WriteLine("{0}: ", reader.GetInt32(0));

                     if (await reader.IsDBNullAsync(1)) {
                        Console.WriteLine("\t(NULL)");
                     }
                     else {
                        using (XmlReader xmlReader = reader.GetXmlReader(1)) {
                           int depth = 1;
                           // NOTE: The XmlReader returned by GetXmlReader does NOT support async operations
                           // See the example below (PrintXmlValuesViaNVarChar) for how to get an XmlReader with asynchronous capabilities
                           while (xmlReader.Read()) {
                              switch (xmlReader.NodeType) {
                                 case XmlNodeType.Element:
                                    Console.WriteLine("{0}<{1}>", new string('\t', depth), xmlReader.Name);
                                    depth++;
                                    break;
                                 case XmlNodeType.Text:
                                    Console.WriteLine("{0}{1}", new string('\t', depth), xmlReader.Value);
                                    break;
                                 case XmlNodeType.EndElement:
                                    depth--;
                                    Console.WriteLine("{0}</{1}>", new string('\t', depth), xmlReader.Name);
                                    break;
                              }
                           }
                        }
                     }
                  }
               }
            }
         }
      }

      // Application transferring a large Xml Document from SQL Server in .NET 4.5
      // This goes via NVarChar and TextReader to enable asynchronous reading
      private static async Task PrintXmlValuesViaNVarChar() {
         XmlReaderSettings xmlSettings = new XmlReaderSettings() {
            // Async must be explicitly enabled in the XmlReaderSettings otherwise the XmlReader will throw exceptions when async methods are called
            Async = true,
            // Since we will immediately wrap the TextReader we are creating in an XmlReader, we will permit the XmlReader to take care of closing\disposing it
            CloseInput = true,
            // If the Xml you are reading is not a valid document (as per <https://docs.microsoft.com/previous-versions/dotnet/netframework-4.0/6bts1x50(v=vs.100)>) you will need to set the conformance level to Fragment
            ConformanceLevel = ConformanceLevel.Fragment
         };

         using (SqlConnection connection = new SqlConnection(connectionString)) {
            await connection.OpenAsync();

            // Cast the XML into NVarChar to enable GetTextReader - trying to use GetTextReader on an XML type will throw an exception
            using (SqlCommand command = new SqlCommand("SELECT [id], CAST([xmldata] AS NVARCHAR(MAX)) FROM [Streams]", connection)) {

               // The reader needs to be executed with the SequentialAccess behavior to enable network streaming
               // Otherwise ReadAsync will buffer the entire Xml Document into memory which can cause scalability issues or even OutOfMemoryExceptions
               using (SqlDataReader reader = await command.ExecuteReaderAsync(CommandBehavior.SequentialAccess)) {
                  while (await reader.ReadAsync()) {
                     Console.WriteLine("{0}:", reader.GetInt32(0));

                     if (await reader.IsDBNullAsync(1)) {
                        Console.WriteLine("\t(NULL)");
                     }
                     else {
                        // Grab the row as a TextReader, then create an XmlReader on top of it
                        // We are not keeping a reference to the TextReader since the XmlReader is created with the "CloseInput" setting (so it will close the TextReader when needed)
                        using (XmlReader xmlReader = XmlReader.Create(reader.GetTextReader(1), xmlSettings)) {
                           int depth = 1;
                           // The XmlReader above now supports asynchronous operations, so we can use ReadAsync here
                           while (await xmlReader.ReadAsync()) {
                              switch (xmlReader.NodeType) {
                                 case XmlNodeType.Element:
                                    Console.WriteLine("{0}<{1}>", new string('\t', depth), xmlReader.Name);
                                    depth++;
                                    break;
                                 case XmlNodeType.Text:
                                    // Depending on what your data looks like, you should either use Value or GetValueAsync
                                    // Value has less overhead (since it doesn't create a Task), but it may also block if additional data is required
                                    Console.WriteLine("{0}{1}", new string('\t', depth), await xmlReader.GetValueAsync());
                                    break;
                                 case XmlNodeType.EndElement:
                                    depth--;
                                    Console.WriteLine("{0}</{1}>", new string('\t', depth), xmlReader.Name);
                                    break;
                              }
                           }
                        }
                     }
                  }
               }
            }
         }
      }
   }
}

샘플-SQL Server로 스트리밍Sample -- Streaming to SQL Server

다음 Transact-sql을 사용 하 여 예제 데이터베이스를 만듭니다.Use the following Transact-SQL to create the sample database:

CREATE DATABASE [Demo2]
GO
USE [Demo2]
GO
CREATE TABLE [BinaryStreams] (
[id] INT PRIMARY KEY IDENTITY(1, 1),
[bindata] VARBINARY(MAX))
GO
CREATE TABLE [TextStreams] (
[id] INT PRIMARY KEY IDENTITY(1, 1),
[textdata] NVARCHAR(MAX))
GO
CREATE TABLE [BinaryStreamsCopy] (
[id] INT PRIMARY KEY IDENTITY(1, 1),
[bindata] VARBINARY(MAX))
GO

이 샘플에서는 다음 작업의 수행 방법을 보여 줍니다.The sample shows how to do the following:

  • 4.5 .NET Framework에서 SQL Server으로 대량 BLOB을 전송 합니다.Transferring a large BLOB to SQL Server in .NET Framework 4.5.

  • 4.5 .NET Framework에서 SQL Server에 대 한 많은 텍스트 파일 전송Transferring a large text file to SQL Server in .NET Framework 4.5.

  • 새로운 비동기 기능을 사용하여 큰 BLOB를 전송합니다.Using the new asynchronous feature to transfer a large BLOB.

  • 새로운 비동기 기능과 await 키워드를 사용하여 큰 BLOB를 전송합니다.Using the new asynchronous feature and the await keyword to transfer a large BLOB.

  • 대량 BLOB의 전송을 취소 하 고 있습니다.Cancelling the transfer of a large BLOB.

  • 새 비동기 기능을 사용 하 여 한 SQL Server에서 다른으로 스트리밍Streaming from one SQL Server to another using the new asynchronous feature.

using System;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace StreamingToServer {
   class Program {
      // Replace the connection string if needed, for instance to connect to SQL Express: @"Server=(local)\SQLEXPRESS;Database=Demo2;Integrated Security=true"
      private const string connectionString = @"Server=(localdb)\V11.0;Database=Demo2";

      static void Main(string[] args) {
         CreateDemoFiles();

         StreamBLOBToServer().Wait();
         StreamTextToServer().Wait();

         // Create a CancellationTokenSource that will be cancelled after 100ms
         // Typically this token source will be cancelled by a user request (e.g. a Cancel button)
         CancellationTokenSource tokenSource = new CancellationTokenSource();
         tokenSource.CancelAfter(100);
         try {
            CancelBLOBStream(tokenSource.Token).Wait();
         }
         catch (AggregateException ex) {
            // Cancelling an async operation will throw an exception
            // Since we are using the Task's Wait method, this exception will be wrapped in an AggregateException
            // If you were using the 'await' keyword, the compiler would take care of unwrapping the AggregateException
            // Depending on when the cancellation occurs, you can either get an error from SQL Server or from .Net
            if ((ex.InnerException is SqlException) || (ex.InnerException is TaskCanceledException)) {
               // This is an expected exception
               Console.WriteLine("Got expected exception: {0}", ex.InnerException.Message);
            }
            else {
               // Did not expect this exception - re-throw it
               throw;
            }
         }

         Console.WriteLine("Done");
      }

      // This is used to generate the files which are used by the other sample methods
      private static void CreateDemoFiles() {
         Random rand = new Random();
         byte[] data = new byte[1024];
         rand.NextBytes(data);

         using (FileStream file = File.Open("binarydata.bin", FileMode.Create)) {
            file.Write(data, 0, data.Length);
         }

         using (StreamWriter writer = new StreamWriter(File.Open("textdata.txt", FileMode.Create))) {
            writer.Write(Convert.ToBase64String(data));
         }
      }

      // Application transferring a large BLOB to SQL Server in .NET 4.5
      private static async Task StreamBLOBToServer() {
         using (SqlConnection conn = new SqlConnection(connectionString)) {
            await conn.OpenAsync();
            using (SqlCommand cmd = new SqlCommand("INSERT INTO [BinaryStreams] (bindata) VALUES (@bindata)", conn)) {
               using (FileStream file = File.Open("binarydata.bin", FileMode.Open)) {

                  // Add a parameter which uses the FileStream we just opened
                  // Size is set to -1 to indicate "MAX"
                  cmd.Parameters.Add("@bindata", SqlDbType.Binary, -1).Value = file;

                  // Send the data to the server asynchronously
                  await cmd.ExecuteNonQueryAsync();
               }
            }
         }
      }

      // Application transferring a large Text File to SQL Server in .NET 4.5
      private static async Task StreamTextToServer() {
         using (SqlConnection conn = new SqlConnection(connectionString)) {
            await conn.OpenAsync();
            using (SqlCommand cmd = new SqlCommand("INSERT INTO [TextStreams] (textdata) VALUES (@textdata)", conn)) {
               using (StreamReader file = File.OpenText("textdata.txt")) {

                  // Add a parameter which uses the StreamReader we just opened
                  // Size is set to -1 to indicate "MAX"
                  cmd.Parameters.Add("@textdata", SqlDbType.NVarChar, -1).Value = file;

                  // Send the data to the server asynchronously
                  await cmd.ExecuteNonQueryAsync();
               }
            }
         }
      }

      // Cancelling the transfer of a large BLOB
      private static async Task CancelBLOBStream(CancellationToken cancellationToken) {
         using (SqlConnection conn = new SqlConnection(connectionString)) {
            // We can cancel not only sending the data to the server, but also opening the connection
            await conn.OpenAsync(cancellationToken);

            // Artificially delay the command by 100ms
            using (SqlCommand cmd = new SqlCommand("WAITFOR DELAY '00:00:00:100';INSERT INTO [BinaryStreams] (bindata) VALUES (@bindata)", conn)) {
               using (FileStream file = File.Open("binarydata.bin", FileMode.Open)) {

                  // Add a parameter which uses the FileStream we just opened
                  // Size is set to -1 to indicate "MAX"
                  cmd.Parameters.Add("@bindata", SqlDbType.Binary, -1).Value = file;

                  // Send the data to the server asynchronously
                  // Pass the cancellation token such that the command will be cancelled if needed
                  await cmd.ExecuteNonQueryAsync(cancellationToken);
               }
            }
         }
      }
   }
}

샘플-한 SQL Server에서 다른 SQL Server로 스트리밍Sample -- Streaming From One SQL Server to Another SQL Server

이 샘플에서는 취소를 지원 하 여 한 SQL Server에서 다른 BLOB으로 많은 BLOB을 비동기적으로 스트리밍하는 방법을 보여 줍니다.This sample demonstrates how to asynchronously stream a large BLOB from one SQL Server to another, with support for cancellation.

using System;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Threading;
using System.Threading.Tasks;

namespace StreamingFromServerToAnother {
   class Program {
      // Replace the connection string if needed, for instance to connect to SQL Express: @"Server=(local)\SQLEXPRESS;Database=Demo2;Integrated Security=true"
      private const string connectionString = @"Server=(localdb)\V11.0;Database=Demo2";

      static void Main(string[] args) {
         // For this example, we don't want to cancel
         // So we can pass in a "blank" cancellation token
         E2EStream(CancellationToken.None).Wait();

         Console.WriteLine("Done");
      }

      // Streaming from one SQL Server to Another One using the new Async.NET
      private static async Task E2EStream(CancellationToken cancellationToken) {
         using (SqlConnection readConn = new SqlConnection(connectionString)) {
            using (SqlConnection writeConn = new SqlConnection(connectionString)) {

               // Note that we are using the same cancellation token for calls to both connections\commands
               // Also we can start both the connection opening asynchronously, and then wait for both to complete
               Task openReadConn = readConn.OpenAsync(cancellationToken);
               Task openWriteConn = writeConn.OpenAsync(cancellationToken);
               await Task.WhenAll(openReadConn, openWriteConn);

               using (SqlCommand readCmd = new SqlCommand("SELECT [bindata] FROM [BinaryStreams]", readConn)) {
                  using (SqlCommand writeCmd = new SqlCommand("INSERT INTO [BinaryStreamsCopy] (bindata) VALUES (@bindata)", writeConn)) {

                     // Add an empty parameter to the write command which will be used for the streams we are copying
                     // Size is set to -1 to indicate "MAX"
                     SqlParameter streamParameter = writeCmd.Parameters.Add("@bindata", SqlDbType.Binary, -1);

                     // The reader needs to be executed with the SequentialAccess behavior to enable network streaming
                     // Otherwise ReadAsync will buffer the entire BLOB into memory which can cause scalability issues or even OutOfMemoryExceptions
                     using (SqlDataReader reader = await readCmd.ExecuteReaderAsync(CommandBehavior.SequentialAccess, cancellationToken)) {
                        while (await reader.ReadAsync(cancellationToken)) {
                           // Grab a stream to the binary data in the source database
                           using (Stream dataStream = reader.GetStream(0)) {

                              // Set the parameter value to the stream source that was opened
                              streamParameter.Value = dataStream;

                              // Asynchronously send data from one database to another
                              await writeCmd.ExecuteNonQueryAsync(cancellationToken);
                           }
                        }
                     }
                  }
               }
            }
         }
      }
   }
}

참고자료See also