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Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here.

How to: Write a Binary File 

The following code example demonstrates writing binary data to a file. Two classes from the System.IO namespace are used: FileStream and BinaryWriter. FileStream represents the actual file, while BinaryWriter provides an interface to the stream that allows binary access.

The following code example writes a file containing integers in binary format. This file can be read with the code in How to: Read a Binary File.


// binary_write.cpp
// compile with: /clr
using namespace System;
using namespace System::IO;

int main()
   array<Int32>^ data = {1, 2, 3, 10000};

   FileStream^ fs = gcnew FileStream("data.bin", FileMode::Create);
   BinaryWriter^ w = gcnew BinaryWriter(fs);

      Console::WriteLine("writing data to file:");
      for (int i=0; i<data->Length; i++)
   catch (Exception^) 
     Console::WriteLine("data could not be written");
     return -1;

   return 0;

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