IsolatedStorageFileStream.IsAsync Property
Definition
Important
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Gets a Boolean value indicating whether the IsolatedStorageFileStream object was opened asynchronously or synchronously.
public:
virtual property bool IsAsync { bool get(); };public override bool IsAsync { get; }member this.IsAsync : boolPublic Overrides ReadOnly Property IsAsync As BooleanProperty Value
true if the IsolatedStorageFileStream object supports asynchronous access; otherwise, false.
Examples
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.
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.
public double SetNewPrefsForUser()
{
try
{
byte inputChar;
IsolatedStorageFile isoFile = IsolatedStorageFile.GetStore(IsolatedStorageScope.User |
IsolatedStorageScope.Assembly |
IsolatedStorageScope.Domain,
typeof(System.Security.Policy.Url),
typeof(System.Security.Policy.Url));
// If this is not a new user, archive the old preferences and
// overwrite them using the new preferences.
if (!this.myNewPrefs)
{
if (isoFile.GetDirectoryNames("Archive").Length == 0)
{
isoFile.CreateDirectory("Archive");
}
else
{
IsolatedStorageFileStream source =
new IsolatedStorageFileStream(this.userName, FileMode.OpenOrCreate,
isoFile);
// This is the stream from which data will be read.
Console.WriteLine("Is the source file readable? " + (source.CanRead ? "true" : "false"));
Console.WriteLine("Creating new IsolatedStorageFileStream for Archive.");
// Open or create a writable file.
IsolatedStorageFileStream target =
new IsolatedStorageFileStream("Archive\\ " + this.userName,
FileMode.OpenOrCreate,
FileAccess.Write,
FileShare.Write,
isoFile);
Console.WriteLine("Is the target file writable? " + (target.CanWrite ? "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(inputChar);
}
// Determine the size of the IsolatedStorageFileStream
// by checking its Length property.
Console.WriteLine("Total Bytes Read: " + source.Length);
}
// After you have read and written to the streams, close them.
target.Close();
source.Close();
}
}
// Open or create a writable file with a maximum size of 10K.
IsolatedStorageFileStream isoStream =
new IsolatedStorageFileStream(this.userName,
FileMode.OpenOrCreate,
FileAccess.Write,
FileShare.Write,
10240,
isoFile);
isoStream.Position = 0; // Position to overwrite the old data.
Public Function SetNewPrefsForUser() As Double
Try
Dim inputChar As Byte
Dim isoFile As IsolatedStorageFile = IsolatedStorageFile.GetStore(IsolatedStorageScope.User Or _
IsolatedStorageScope.Assembly Or IsolatedStorageScope.Domain, _
GetType(System.Security.Policy.Url), GetType(System.Security.Policy.Url))
' If this is not a new user, archive the old preferences and
' overwrite them using the new preferences.
If Not Me.myNewPrefs Then
If isoFile.GetDirectoryNames("Archive").Length = 0 Then
isoFile.CreateDirectory("Archive")
Else
Dim source As New IsolatedStorageFileStream(Me.userName, FileMode.OpenOrCreate, isoFile)
Dim canWrite, canRead As Boolean
' This is the stream from which data will be read.
If source.CanRead Then canRead = True Else canRead = False
Console.WriteLine("Is the source file readable? " & canRead)
Console.WriteLine("Creating new IsolatedStorageFileStream for Archive.")
' Open or create a writable file.
Dim target As New IsolatedStorageFileStream("Archive\ " & Me.userName, _
FileMode.OpenOrCreate, FileAccess.Write, FileShare.Write, isoFile)
' This is the stream to which data will be written.
If target.CanWrite Then canWrite = True Else canWrite = False
Console.WriteLine("Is the target file writable? " & canWrite)
target.SetLength(0) 'rewind the target file
' Stream the old file to a new file in the Archive directory.
If source.IsAsync And target.IsAsync Then
' 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 = CByte(source.ReadByte())
target.WriteByte(inputChar)
End While
' Determine the size of the IsolatedStorageFileStream
' by checking its Length property.
Console.WriteLine(("Total Bytes Read: " & source.Length))
End If
' After you have read and written to the streams, close them.
target.Close()
source.Close()
End If
End If
' Open or create a writable file with a maximum size of 10K.
Dim isoStream As New IsolatedStorageFileStream(Me.userName, FileMode.OpenOrCreate, _
FileAccess.Write, FileShare.Write, 10240, isoFile)
isoStream.SetLength(0) 'Position to overwrite the old data.
Remarks
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.
Applies to
See also
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