UnmanagedMemoryStream.CanWrite Propriedade
Definição
Obtém um valor que indica se um fluxo oferece suporte à gravação.Gets a value indicating whether a stream supports writing.
public:
virtual property bool CanWrite { bool get(); };
public override bool CanWrite { get; }
member this.CanWrite : bool
Public Overrides ReadOnly Property CanWrite As Boolean
Valor da propriedade
false Se o objeto foi criado por um construtor com um access valor de parâmetro que dá suporte à gravação ou foi criado por um construtor que não tinha parâmetros, ou se o fluxo estiver fechado; caso contrário, true .false if the object was created by a constructor with an access parameter value that supports writing or was created by a constructor that had no parameters, or if the stream is closed; otherwise, true.
Exemplos
O exemplo de código a seguir demonstra como ler e gravar na memória não gerenciada usando a UnmanagedMemoryStream classe.The following code example demonstrates how to read from and write to unmanaged memory using the UnmanagedMemoryStream class. Um bloco de memória não gerenciada é alocado e desalocado usando a Marshal classe.A block of unmanaged memory is allocated and de-allocated using the Marshal class. Neste exemplo, um UnmanagedMemoryStream objeto é passado para um método que verifica a CanWrite propriedade antes de tentar gravar os dados no fluxo.In this example, an UnmanagedMemoryStream object is passed to a method which checks the CanWrite property before attempting to write the data to the stream.
// Note: You must compile this sample using the unsafe flag.
// From the command line, type the following: csc sample.cs /unsafe
using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
unsafe class Program
{
static void Main()
{
// Create some data to write.
byte[] text = UnicodeEncoding.Unicode.GetBytes("Data to write.");
// Allocate a block of unmanaged memory.
IntPtr memIntPtr = Marshal.AllocHGlobal(text.Length);
// Get a byte pointer from the unmanaged memory block.
byte* memBytePtr = (byte*)memIntPtr.ToPointer();
UnmanagedMemoryStream writeStream =
new UnmanagedMemoryStream(
memBytePtr, text.Length, text.Length, FileAccess.Write);
// Write the data.
WriteToStream(writeStream, text);
// Close the stream.
writeStream.Close();
// Create another UnmanagedMemoryStream for reading.
UnmanagedMemoryStream readStream =
new UnmanagedMemoryStream(memBytePtr, text.Length);
// Display the contents of the stream to the console.
PrintStream(readStream);
// Close the reading stream.
readStream.Close();
// Free up the unmanaged memory.
Marshal.FreeHGlobal(memIntPtr);
}
public static void WriteToStream(UnmanagedMemoryStream writeStream, byte[] text)
{
// Verify that the stream is writable:
// By default, UnmanagedMemoryStream objects do not have write access,
// write access must be set explicitly.
if (writeStream.CanWrite)
{
// Write the data, byte by byte
for (int i = 0; i < writeStream.Length; i++)
{
writeStream.WriteByte(text[i]);
}
}
}
public static void PrintStream(UnmanagedMemoryStream readStream)
{
byte[] text = new byte[readStream.Length];
// Verify that the stream is writable:
// By default, UnmanagedMemoryStream objects do not have write access,
// write access must be set explicitly.
if (readStream.CanRead)
{
// Write the data, byte by byte
for (int i = 0; i < readStream.Length; i++)
{
text[i] = (byte)readStream.ReadByte();
}
}
Console.WriteLine(UnicodeEncoding.Unicode.GetString(text));
}
}
Comentários
Essa propriedade indica se o objeto de fluxo atual oferece suporte à gravação.This property indicates whether the current stream object supports writing.