C# 0 The Complete Reference

Using MemoryStream

Sometimes it is useful to read input from or to write output to an array, rather than directly 

from or to a device. To do this, you will use 

MemoryStream

.

MemoryStream

 is an 

implementation of 

Stream

 that uses an array of bytes for input and/or output. 

MemoryStream

 defines several constructors. Here is the one we will use:

MemoryStream(byte[ ] 

buf

)

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Here, 

buf

 is an array of bytes that will be used for the source and/or target of I/O requests. 

The stream created by this constructor can be written or read, and supports 

Seek( )

. When 

using this constructor, you must remember to make 

buf

 large enough to hold whatever 

output you will be directing to it.

Here is a program that demonstrates the use of 

MemoryStream

:

// Demonstrate MemoryStream.

using System;

using System.IO;

class MemStrDemo {

  static void Main() {

    byte[] storage = new byte[255];

    // Create a memory-based stream.

    MemoryStream memstrm = new MemoryStream(storage);

    // Wrap memstrm in a reader and a writer.

    StreamWriter memwtr = new StreamWriter(memstrm);

    StreamReader memrdr = new StreamReader(memstrm);

    // Write to storage, through memwtr.

    for(int i=0; i < 10; i++)

       memwtr.WriteLine("byte [" + i + "]: " + i);

    // Put a period at the end.

    memwtr.WriteLine(".");

    memwtr.Flush();

    Console.WriteLine("Reading from storage directly: ");

    // Display contents of storage directly.

    foreach(char ch in storage) {

      if (ch == '.') break;

      Console.Write(ch);

    }

    Console.WriteLine("\nReading through memrdr: ");

    // Read from memstrm using the stream reader.

    memstrm.Seek(0, SeekOrigin.Begin); // reset file pointer

    string str = memrdr.ReadLine();

    while(str != null) {

      str = memrdr.ReadLine();

      if(str.CompareTo(".") == 0) break;

      Console.WriteLine(str);

    }

  }

}

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The output from the program is shown here:

Reading from storage directly:

byte [0]: 0

byte [1]: 1

byte [2]: 2

byte [3]: 3

byte [4]: 4

byte [5]: 5

byte [6]: 6

byte [7]: 7

byte [8]: 8

byte [9]: 9

Reading through memrdr:

byte [1]: 1

byte [2]: 2

byte [3]: 3

byte [4]: 4

byte [5]: 5

byte [6]: 6

byte [7]: 7

byte [8]: 8

byte [9]: 9

In the program, an array of bytes called 

storage

 is created. This array is then used as the 

underlying storage for a