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UnmanagedMemoryStream Constructor (Byte*, Int64)


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Initializes a new instance of the UnmanagedMemoryStream class using the specified location and memory length.

This API is not CLS-compliant.

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

public unsafe UnmanagedMemoryStream(
	byte* pointer,
	long length


Type: System.Byte*

A pointer to an unmanaged memory location.

Type: System.Int64

The length of the memory to use.

Exception Condition

The user does not have the required permission.


The pointer value is null.


The length value is less than zero.

- or -

The length is large enough to cause an overflow.

This constructor creates a new instance of the UnmanagedMemoryStream class, and by default sets the CanWrite property to false and the CanRead property to true. The Length property is set to the value of the length parameter and cannot be changed.

The following code example demonstrates how to read from and write to unmanaged memory using the UnmanagedMemoryStream class. A block of unmanaged memory is allocated and de-allocated using the Marshal class.

// 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.

        // Create another UnmanagedMemoryStream for reading.
        UnmanagedMemoryStream readStream =
            new UnmanagedMemoryStream(memBytePtr, text.Length);

        // Display the contents of the stream to the console.

        // Close the reading stream.

        // Free up the unmanaged memory.


    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++)

    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();



for accessing unmanaged memory.


requires full trust for the immediate caller. This member cannot be used by partially trusted or transparent code.

Universal Windows Platform
Available since 10
.NET Framework
Available since 2.0
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