<serviceDebug 
            httpHelpPageEnabled="true" 
            includeExceptionDetailInFaults="true"
          />

using (SqlConnection connection = new SqlConnection(connStringBuilder.ToString()))
            {
                connection.Open();

                SqlCommand command = new SqlCommand("SELECT TOP(1) Photo.PathName(), GET_FILESTREAM_TRANSACTION_CONTEXT() FROM employees", connection);
//понятно, что GET_FILESTREAM_TRANSACTION_CONTEXT  возвращает токен, который представляет текущий контекст транзакции сеанса. Этот токен используется приложением для связывания потоковых операций FILESTREAM файловой системы с транзакцией.
но что конкретно он делает и зачем - не понятно.
                SqlTransaction tran = connection.BeginTransaction(IsolationLevel.ReadCommitted);
                command.Transaction = tran;

                using (SqlDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        // Get the pointer for file 
                        string path = reader.GetString(0);//вот тут вообще непонятно откуда какой путь берется
                        byte[] transactionContext = reader.GetSqlBytes(1).Buffer; 

                        // Create the SqlFileStream
                        using (Stream fileStream = new SqlFileStream(path, transactionContext, FileAccess.Write, FileOptions.SequentialScan, allocationSize: 0))
                        {
                            // Write a single byte to the file. This will replace any data in the file.
                            fileStream.WriteByte(0x01); //и вот снова - запись байта!
                        }
                    }
                }
                tran.Commit();
            }

INSERT INTO Archive.dbo.Records
    VALUES (newid (), 3, 
      CAST ('Seismic Data' as varbinary(max)));
GO

public void InsertFile(string fileName)
{
	if (!File.Exists(fileName)) return;
	var content = File.ReadAllBytes(fileNam);
	using(var connection = new SqlConnection("connection string"))
	{
		using(var command = new SqlCommand(connection, "insert into MyFileTable (file_guid, file_content) values (@file_guid, @file_content)"))
		{
			command.Parameters.AddWithValue("@file_guid", Guid.NewGuid());
			command.Parameters.AddWithValue("@file_content", content);
			
			command.ExecuteNonQuery();
		}
	}
}
Вот к чему привела вставка файла в 1,5 Гб...
System.OutOfMemoryException was unhandled
  HResult=-2147024882
  Message=Exception of type 'System.OutOfMemoryException' was thrown.
  Source=mscorlib
  StackTrace:
       at System.IO.File.InternalReadAllBytes(String path, Boolean checkHost)
       at System.IO.File.ReadAllBytes(String path)
       at WindowsFormsApplication1.Form1.button7_Click(Object sender, EventArgs e) in c:\Users\Administrator\Desktop\WindowsFormsApplication1\WindowsFormsApplication1\Form1.cs:line 223
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at WindowsFormsApplication1.Program.Main() in c:\Users\Administrator\Desktop\WindowsFormsApplication1\WindowsFormsApplication1\Program.cs:line 19
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: 

using(var reader = command.ExecuteReader())
					{
						if (reader.Read())
						{
							var path = reader.GetString(0);
							var transactionContext = reader.GetSqlBytes(1).Buffer;

							using (Stream fileStream = new SqlFileStream(path, transactionContext, FileAccess.Write))
							{
								var buffer = new byte[10 * 1024 * 1024]; //buffer size = 10 MB;
								var readed = 0;
								while((readed = stream.Read(buffer, 0, buffer.Length)) != 0)
								{
									fileStream.Write(buffer, 0, readed);
									fileStream.Flush();
								}
							}
						}
					}

public void InsertFile(string fileName)
        {
            if (!File.Exists(fileName)) return;
            using (var stream = File.OpenRead(fileName))
            {
                using (var connection = new SqlConnection("Server=localhost;initial catalog=FileServiceDB;integrated security=SSPI"))
                {
                    connection.Open();
                    using (var transaction = connection.BeginTransaction(System.Data.IsolationLevel.ReadCommitted))
                    {
                        using (var command = new SqlCommand("insert into employees (EmployeeID, Photos, RowGuid) output INSERTED.Photos.PathName(), GET_FILESTREAM_TRANSACTION_CONTEXT() values ('2', @file_content, @file_guid)", connection, transaction))
                        {
                            command.Parameters.AddWithValue("@file_content", new byte[0]);
                            command.Parameters.AddWithValue("@file_guid", Guid.NewGuid());
                            

                            using (var reader = command.ExecuteReader())
                            {
                                if (reader.Read())
                                {
                                    var path = reader.GetString(0);
                                    var transactionContext = reader.GetSqlBytes(1).Buffer;

                                    using (Stream fileStream = new SqlFileStream(path, transactionContext, FileAccess.Write))
                                    {
                                        var buffer = new byte[10 * 1024 * 1024]; //buffer size = 10 MB;
                                        var readed = 0;
                                        while ((readed = stream.Read(buffer, 0, buffer.Length)) != 0)
                                        {
                                            fileStream.Write(buffer, 0, readed);
                                            fileStream.Flush();
                                        }
                                    }
                                }
                            }

                        }

                        transaction.Commit();
                    }
                }
            }
            MessageBox.Show("Done");
        }

System.IO.IOException was unhandled
  HResult=-2146232800
  Message=An exception has been thrown when reading the stream.
  Source=System.ServiceModel
  StackTrace:
       at System.ServiceModel.Dispatcher.StreamFormatter.MessageBodyStream.Read(Byte[] buffer, Int32 offset, Int32 count)
       at WpfClient.MainWindow.<>c__DisplayClass16.<DownloadMethod>b__12() in c:\Users\Administrator\Desktop\!New.Project\MyTest\FileServiceLib\WpfClient\MainWindow.xaml.cs:line 273
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: System.ServiceModel.CommunicationException
       HResult=-2146233087
       Message=The socket connection was aborted. This could be caused by an error processing your message or a receive timeout being exceeded by the remote host, or an underlying network resource issue. Local socket timeout was '00:20:00'.
       Source=System.ServiceModel
       StackTrace:
            at System.ServiceModel.Channels.HttpInput.WebResponseHttpInput.WebResponseInputStream.Read(Byte[] buffer, Int32 offset, Int32 count)
            at System.ServiceModel.Channels.MaxMessageSizeStream.Read(Byte[] buffer, Int32 offset, Int32 count)
            at System.IO.BufferedStream.Read(Byte[] array, Int32 offset, Int32 count)
            at System.Xml.EncodingStreamWrapper.Read(Byte[] buffer, Int32 offset, Int32 count)
            at System.Xml.XmlBufferReader.TryEnsureBytes(Int32 count)
            at System.Xml.XmlBufferReader.GetBuffer(Int32 count, Int32& offset, Int32& offsetMax)
            at System.Xml.XmlUTF8TextReader.ReadText(Boolean hasLeadingByteOf0xEF)
            at System.Xml.XmlUTF8TextReader.Read()
            at System.Xml.XmlBaseReader.MoveToContent()
            at System.ServiceModel.Dispatcher.StreamFormatter.MessageBodyStream.Read(Byte[] buffer, Int32 offset, Int32 count)
       InnerException: System.IO.IOException
            HResult=-2146232800
            Message=Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.
            Source=System
            StackTrace:
                 at System.Net.ConnectStream.Read(Byte[] buffer, Int32 offset, Int32 size)
                 at System.ServiceModel.Channels.PreReadStream.Read(Byte[] buffer, Int32 offset, Int32 count)
                 at System.ServiceModel.Channels.HttpInput.WebResponseHttpInput.WebResponseInputStream.Read(Byte[] buffer, Int32 offset, Int32 count)
            InnerException: System.Net.Sockets.SocketException
                 HResult=-2147467259
                 Message=An existing connection was forcibly closed by the remote host
                 Source=System
                 ErrorCode=10054
                 NativeErrorCode=10054
                 StackTrace:
                      at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
                      at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
                 InnerException: 

<?xml version="1.0"   encoding="utf-8"   ?>
<configuration>
  <system.transactions>
    <defaultSettings timeout="23:50:00"/>
  </system.transactions>
  <system.serviceModel>
        
      <messageLogging logMalformedMessages="true" logMessagesAtTransportLevel="true" />
    </diagnostics>
    <services>
      <service name="FileServiceLib.FileService"
      behaviorConfiguration="FileServiceMEXBehavior" >
        
        <endpoint address="" 
        binding="basicHttpBinding"
                  bindingConfiguration="customBinding"
        contract="FileServiceLib.IFileService" behaviorConfiguration="endpointBehavior" />
        
        <!-- Включить конечную точку МЕХ -->
        <endpoint address="mex"
        binding="mexHttpBinding"
        contract="IMetadataExchange"  />

        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:1825/FileService"  />
          </baseAddresses>
        </host>
      </service>
    </services>    
    <bindings>
      <basicHttpBinding>
        <binding name="customBinding"
                 
                 maxReceivedMessageSize="9223372036854775807"   
                
          maxBufferSize="2147483647"

          sendTimeout="24.20:31:23.6470000"
          closeTimeout="20:20:00"
          openTimeout="21:20:00"
          receiveTimeout="24.20:31:23.6470000"
          maxBufferPoolSize="2147483647"
          transferMode="Streamed" >
          <security mode="None">
            <transport clientCredentialType="None"  />
           
          </security>
          
        </binding>
      </basicHttpBinding>
      
    </bindings>
        <!--Определение поведения для МЕХ-->
    <behaviors>
      
      <endpointBehaviors>
        <behavior name="endpointBehavior">
          <dataContractSerializer maxItemsInObjectGraph="2147483647"/>
        </behavior>
      </endpointBehaviors>
    
      <serviceBehaviors>
        <behavior name="FileServiceMEXBehavior"  >
          <serviceDebug
            httpHelpPageEnabled="true"
            includeExceptionDetailInFaults="true"  />
          <serviceMetadata httpGetEnabled="true"  />
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
  <connectionStrings>
    <add name="FileServiceDBEntities" connectionString="metadata=res://*/;provider=System.Data.SqlClient;provider connection string="data source=WIN-8PBNCAJO58P;initial catalog=FileServiceDB;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework"" providerName="System.Data.EntityClient" />
  </connectionStrings>
</configuration>

<configuration>
   
      <trace autoflush="true" />
        <sources>
            <source name="System.ServiceModel.MessageLogging" switchValue="Warning,ActivityTracing">
                <listeners>
                    <add type="System.Diagnostics.DefaultTraceListener" name="Default">
                        <filter type="" />
                    </add>
                    <add name="ServiceModelMessageLoggingListener">
                        <filter type="" />
                    </add>
                </listeners>
            </source>
            <source propagateActivity="true" name="System.ServiceModel" switchValue="Warning,ActivityTracing">
                <listeners>
                    <add type="System.Diagnostics.DefaultTraceListener" name="Default">
                        <filter type="" />
                    </add>
                    <add name="ServiceModelTraceListener">
                        <filter type="" />
                    </add>
                </listeners>
            </source>
          
          
            <source name="System.ServiceModel"
                    switchValue="Information, ActivityTracing"
                    propagateActivity="true">
              <listeners>
                <add name="sdt"
                    type="System.Diagnostics.XmlWriterTraceListener"
                    initializeData= "SdrConfigExample.e2e" />
              </listeners>
            </source>
       
        </sources>
        <sharedListeners>
            <add initializeData="c:\users\administrator\desktop\!new.project\mytest\fileservicelib\wpfclient\app_messages.svclog"
                type="System.Diagnostics.XmlWriterTraceListener, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
                name="ServiceModelMessageLoggingListener" traceOutputOptions="Timestamp">
                <filter type="" />
            </add>
            <add initializeData="c:\users\administrator\desktop\!new.project\mytest\fileservicelib\wpfclient\app_tracelog.svclog"
                type="System.Diagnostics.XmlWriterTraceListener, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"
                name="ServiceModelTraceListener" traceOutputOptions="Timestamp">
                <filter type="" />
            </add>
        </sharedListeners>
    </system.diagnostics>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
  <system.transactions>
    <defaultSettings timeout="23:50:00"/>
  </system.transactions>
  <system.serviceModel>

    <bindings>
      <basicHttpBinding>
        <binding name="BasicHttpBinding_IFileService"
                 sendTimeout="24.20:31:23.6470000"
                 receiveTimeout="24.20:31:23.6470000"
                 openTimeout="24.20:31:23.6470000"
                 closeTimeout="24.20:31:23.6470000"
                 maxBufferSize="2147483647"
                 maxReceivedMessageSize="9223372036854775807"
                 maxBufferPoolSize="2147483647"
                 transferMode="Streamed">          
          <security mode="None">
            <transport clientCredentialType="None"  />
            
          </security>
        </binding>
      </basicHttpBinding>
    </bindings>
    <client>
      <endpoint address="http://localhost:1825/FileService" binding="basicHttpBinding"
        bindingConfiguration="BasicHttpBinding_IFileService" contract="ServiceReference1.IFileService"
                behaviorConfiguration="endpointBehavior"
        name="BasicHttpBinding_IFileService" />
    </client>
   <behaviors>
    <endpointBehaviors>
      <behavior name="endpointBehavior">
        <dataContractSerializer maxItemsInObjectGraph="2147483647"/>
      </behavior>
    </endpointBehaviors>
    </behaviors>
    
   
      <messageLogging logMalformedMessages="true" logMessagesAtTransportLevel="true" />
    </diagnostics>
    </system.serviceModel>
  <connectionStrings>
    <add name="FileServiceDBEntities"
         connectionString="metadata=res://*/;provider=System.Data.SqlClient;provider connection string="data source=WIN-8PBNCAJO58P;initial catalog=FileServiceDB;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework"" providerName="System.Data.EntityClient" />
  </connectionStrings>
</configuration>

public FileMessageContract GetFile(DownloadMessage request)
        {
            FileMessageContract result = new FileMessageContract();
            result.fileName = request.fileName;
            var connection = new SqlConnection("Server=localhost;initial catalog=FileServiceDB;integrated security=SSPI");
            connection.Open();
            var transaction = connection.BeginTransaction(System.Data.IsolationLevel.ReadCommitted);
            using (var command = new SqlCommand("SELECT FileStream.PathName() FROM FilesTable Where FileName =@file_name and FolderID=@folder_id", connection, transaction))
            {
                command.Parameters.AddWithValue("@file_name", request.fileName);
                command.Parameters.AddWithValue("@folder_id", request.folderId);

                
                result.filePath = (string)command.ExecuteScalar();
               
                /*  command.CommandText = "SELECT DATALENGTH(FileStream) FROM FilesTable";
                  result.length = (long)command.ExecuteScalar();*/

                command.CommandText = "SELECT GET_FILESTREAM_TRANSACTION_CONTEXT()";
                using (var reader = command.ExecuteReader())
                {
                    if (reader.Read())
                    {
                        var transactionContext = reader.GetSqlBytes(0).Buffer;
                        Stream sqlFileStream = new SqlFileStream(result.filePath, transactionContext, FileAccess.Read);
                        result.length = sqlFileStream.Length;
                        result.fileStream = sqlFileStream;
                    }
                }
            }
            
            /*  transaction.Commit();
               connection.Close(); 
                connection.Dispose();
             transaction.Dispose();*/
            return result;
        }public FileMessageContract GetFile(DownloadMessage request)
        {
            FileMessageContract result = new FileMessageContract();
            result.fileName = request.fileName;
            var connection = new SqlConnection("Server=localhost;initial catalog=FileServiceDB;integrated security=SSPI");
            connection.Open();
            var transaction = connection.BeginTransaction(System.Data.IsolationLevel.ReadCommitted);
            using (var command = new SqlCommand("SELECT FileStream.PathName() FROM FilesTable Where FileName =@file_name and FolderID=@folder_id", connection, transaction))
            {
                command.Parameters.AddWithValue("@file_name", request.fileName);
                command.Parameters.AddWithValue("@folder_id", request.folderId);

                
                result.filePath = (string)command.ExecuteScalar();
               
                /*  command.CommandText = "SELECT DATALENGTH(FileStream) FROM FilesTable";
                  result.length = (long)command.ExecuteScalar();*/

                command.CommandText = "SELECT GET_FILESTREAM_TRANSACTION_CONTEXT()";
                using (var reader = command.ExecuteReader())
                {
                    if (reader.Read())
                    {
                        var transactionContext = reader.GetSqlBytes(0).Buffer;
                        Stream sqlFileStream = new SqlFileStream(result.filePath, transactionContext, FileAccess.Read);
                        result.length = sqlFileStream.Length;
                        result.fileStream = sqlFileStream;
                    }
                }
            }
            
            /*  transaction.Commit();
               connection.Close(); 
                connection.Dispose();
             transaction.Dispose();*/
            return result;
        }

 private void btnDownload_Click(object sender, RoutedEventArgs e)
        {    
            if (SelectedItem().Tag is FilesInfo)
            {
                var id = SelectedItem().Tag as FilesInfo;
                var name = SelectedItem().Header.ToString();
                Thread thread = new Thread(() => DownloadMethod(id, name));
                thread.Start();
            }
        }


public void DownloadMethod(FilesInfo id, string name)
        {
            var buffer = new byte[10 * 1024 * 1024];
            DownloadMessage downloadRequest = new DownloadMessage();
            downloadRequest.fileName = name;
            downloadRequest.folderId = id.FolderID;
            FileMessageContract fileMessage = new FileMessageContract();          
            FileStream fileStream = File.Open(@"C:\" + name, FileMode.Create);

            Thread thr = new Thread(new ThreadStart(() =>
            {
                var path = serviceClient.GetFile(ref downloadRequest.fileName, ref downloadRequest.folderId, out fileMessage.length, out fileMessage.fileStream);                                
                Dispatcher.Invoke(() =>
                {
                    progress.Maximum = fileMessage.length;
                    progress.Value = 0;
                    progress.Visibility = Visibility.Visible;
                });               
                var readed = 0;
          
                    while ((readed = fileMessage.fileStream.Read(buffer, 0, buffer.Length)) != 0)
                    {
                        fileStream.Write(buffer, 0, readed);
                        fileStream.Flush();                       
                        Dispatcher.Invoke(() =>
                        {
                            progress.Value = fileStream.Position;
                        });
                    }            
                Dispatcher.Invoke(() => { progress.Visibility = Visibility.Hidden; });
                MessageBox.Show("Your file was downloaded successfully. It saved on C:\\ drive.");
                fileMessage.fileStream.Dispose();
                fileStream.Dispose();
            }
            ));
            thr.Start();
        }

Error trace record:

<E2ETraceEvent xmlns="http://schemas.microsoft.com/2004/06/E2ETraceEvent">
<System xmlns="http://schemas.microsoft.com/2004/06/windows/eventlog/system">
<EventID>524340</EventID>
<Type>3</Type>
<SubType Name="Error">0</SubType>
<Level>2</Level>
<TimeCreated SystemTime="2014-03-13T11:52:01.3705958Z" />
<Source Name="System.ServiceModel" />
<Correlation ActivityID="{ee9e6942-ae5b-400c-8abd-c21e9b119791}" />
<Execution ProcessName="TestDB.vshost" ProcessID="4936" ThreadID="11" />
<Channel />
<Computer>WIN-8PBNCAJO58P</Computer>
</System>
<ApplicationData>
<TraceData>
<DataItem>
<TraceRecord xmlns="http://schemas.microsoft.com/2004/10/E2ETraceEvent/TraceRecord" Severity="Error">
<TraceIdentifier>http://msdn.microsoft.com/en-US/library/System.ServiceModel.ServiceOperationExceptionOnReply.aspx</TraceIdentifier>
<Description>Replying to an operation threw a exception.</Description>
<AppDomain>TestDB.vshost.exe</AppDomain>
<Source>System.ServiceModel.Dispatcher.ImmutableDispatchRuntime/4878312</Source>
<Exception>
<ExceptionType>System.IO.IOException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</ExceptionType>
<Message>The handle is invalid.
</Message>
<StackTrace>
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.FileStream.ReadCore(Byte[] buffer, Int32 offset, Int32 count)
at System.IO.FileStream.Read(Byte[] array, Int32 offset, Int32 count)
at System.Data.SqlTypes.SqlFileStream.Read(Byte[] buffer, Int32 offset, Int32 count)
at System.Xml.XmlDictionaryWriter.WriteValue(IStreamProvider value)
at System.ServiceModel.Dispatcher.StreamFormatter.Serialize(XmlDictionaryWriter writer, Object[] parameters, Object returnValue)
at System.ServiceModel.Dispatcher.OperationFormatter.SerializeBodyContents(XmlDictionaryWriter writer, MessageVersion version, Object[] parameters, Object returnValue, Boolean isRequest)
at System.ServiceModel.Dispatcher.OperationFormatter.OperationFormatterMessage.OperationFormatterBodyWriter.OnWriteBodyContents(XmlDictionaryWriter writer)
at System.ServiceModel.Channels.BodyWriterMessage.OnWriteBodyContents(XmlDictionaryWriter writer)
at System.ServiceModel.Channels.Message.OnWriteMessage(XmlDictionaryWriter writer)
at System.ServiceModel.Channels.TextMessageEncoderFactory.TextMessageEncoder.WriteMessage(Message message, Stream stream)
at System.ServiceModel.Channels.HttpOutput.WriteStreamedMessage(TimeSpan timeout)
at System.ServiceModel.Channels.HttpOutput.Send(TimeSpan timeout)
at System.ServiceModel.Channels.HttpPipeline.EmptyHttpPipeline.SendReplyCore(Message message, TimeSpan timeout)
at System.ServiceModel.Channels.HttpPipeline.EmptyHttpPipeline.SendReply(Message message, TimeSpan timeout)
at System.ServiceModel.Channels.HttpRequestContext.OnReply(Message message, TimeSpan timeout)
at System.ServiceModel.Channels.RequestContextBase.Reply(Message message, TimeSpan timeout)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.Reply(MessageRpc&amp; rpc)
</StackTrace>
<ExceptionString>System.IO.IOException: The handle is invalid.

   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileStream.ReadCore(Byte[] buffer, Int32 offset, Int32 count)
   at System.IO.FileStream.Read(Byte[] array, Int32 offset, Int32 count)
   at System.Data.SqlTypes.SqlFileStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at System.Xml.XmlDictionaryWriter.WriteValue(IStreamProvider value)
   at System.ServiceModel.Dispatcher.StreamFormatter.Serialize(XmlDictionaryWriter writer, Object[] parameters, Object returnValue)
   at System.ServiceModel.Dispatcher.OperationFormatter.SerializeBodyContents(XmlDictionaryWriter writer, MessageVersion version, Object[] parameters, Object returnValue, Boolean isRequest)
   at System.ServiceModel.Dispatcher.OperationFormatter.OperationFormatterMessage.OperationFormatterBodyWriter.OnWriteBodyContents(XmlDictionaryWriter writer)
   at System.ServiceModel.Channels.BodyWriterMessage.OnWriteBodyContents(XmlDictionaryWriter writer)
   at System.ServiceModel.Channels.Message.OnWriteMessage(XmlDictionaryWriter writer)

 public class FileService:IFileService
    {
        private static SqlConnection conn;
        private static SqlTransaction trn;
       
       ...
         
        public FileMessageContract GetFile(DownloadMessage request)
        {
            ...
            var connection = new SqlConnection("Server=localhost;initial catalog=FileServiceDB;integrated security=SSPI;Connection Timeout=65536");
            connection.Open();
            conn = connection;            
            var transaction = connection.BeginTransaction(System.Data.IsolationLevel.ReadCommitted);
            trn = transaction;

 [ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
    public class FileService:IFileService
    {
        private static SqlConnection conn;
        private static SqlTransaction trn;