IsolatedStorageFileStream::IsAsync Property

.NET Framework (current version)
 

Gets a Boolean value indicating whether the IsolatedStorageFileStream object was opened asynchronously or synchronously.

Namespace:   System.IO.IsolatedStorage
Assembly:  mscorlib (in mscorlib.dll)

C#
C++
F#
VB
Copy 
public:
property bool IsAsync {
	virtual bool get() override;
}

Property Value

Type: System::Boolean

true if the IsolatedStorageFileStream object supports asynchronous access; otherwise, false.

Asynchronous IsolatedStorageFileStream objects cannot be created, unlike FileStream. However, the BeginWrite, BeginRead, EndWrite, and EndRead methods are supported on synchronous instances, with some performance penalties.

The following code example demonstrates how you can use the IsAsync property to verify that an IsolatedStorageFileStream is synchronous. For the complete context of this example, see the IsolatedStorageFileStream overview.

C#
C++
VB
Copy 
double SetNewPrefsForUser()
{
   try
   {
      Byte inputChar;
      IsolatedStorageFile^ isoFile = IsolatedStorageFile::GetStore( static_cast<IsolatedStorageScope>(IsolatedStorageScope::User | IsolatedStorageScope::Assembly | IsolatedStorageScope::Domain), System::Security::Policy::Url::typeid, System::Security::Policy::Url::typeid );

      // If this is not a new user, archive the old preferences and 
      // overwrite them using the new preferences.
      if (  !this->NewPrefs )
      {
         if ( isoFile->GetDirectoryNames( "Archive" )->Length == 0 )
                     isoFile->CreateDirectory( "Archive" );
         else
         {

            // This is the stream to which data will be written.
            IsolatedStorageFileStream^ source = gcnew IsolatedStorageFileStream( this->userName,FileMode::OpenOrCreate,isoFile );

            // This is the stream from which data will be read.
            Console::WriteLine( "Is the source file readable?  {0}", (source->CanRead ? (String^)"true" : "false") );
            Console::WriteLine( "Creating new IsolatedStorageFileStream for Archive." );

            // Open or create a writable file.
            IsolatedStorageFileStream^ target = gcnew IsolatedStorageFileStream( String::Concat("Archive\\",this->userName),FileMode::OpenOrCreate,FileAccess::Write,FileShare::Write,isoFile );

            Console::WriteLine( "Is the target file writable? {0}", (target->CanWrite ? (String^)"true" : "false") );

            // Stream the old file to a new file in the Archive directory.
            if ( source->IsAsync && target->IsAsync )
            {

               // IsolatedStorageFileStreams cannot be asynchronous.  However, you
               // can use the asynchronous BeginRead and BeginWrite functions
               // with some possible performance penalty.
               Console::WriteLine( "IsolatedStorageFileStreams cannot be asynchronous." );
            }
            else
            {

               Console::WriteLine( "Writing data to the new file." );
               while ( source->Position < source->Length )
               {
                  inputChar = (Byte)source->ReadByte();
                  target->WriteByte( (Byte)source->ReadByte() );
               }

               // Determine the size of the IsolatedStorageFileStream
               // by checking its Length property.
               Console::WriteLine( "Total Bytes Read: {0}", source->Length.ToString() );

            }

            // After you have read and written to the streams, close them.
            target->Close();
            source->Close();
         }
      }

      // Open or create a writable file, no larger than 10k
      IsolatedStorageFileStream^ isoStream = gcnew IsolatedStorageFileStream( this->userName,FileMode::OpenOrCreate,FileAccess::Write,FileShare::Write,10240,isoFile );

      isoStream->Position = 0; // Position to overwrite the old data.

.NET Framework
Available since 1.1
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