How to create a Binary File in C#

The System.IO.BinaryWriter class writes binary data to a stream. This class also provides an option to specify the character encoding, including ASCII, Unicode, UTF32, UTF7, and UTF8 encoding. 

Create a BinaryWriter

The BinaryWriter constructor has overloaded forms to support a stream and encoding.  The following code snippet creates BinaryWriter objects with a stream and character encoding format. 

string fileName = @"C:\temp\MC.bin";                  
BinaryWriter bwStream = 
new BinaryWriter(new FileStream(fileName,FileMode.Create));  
  
Encoding ascii = Encoding.ASCII;  
BinaryWriter bwEncoder = 
new BinaryWriter(new FileStream(fileName, FileMode.Create), ascii);  

Writing Binary to a Stream

The Write overloaded method writes primitive data types to a stream. The Write method can write Boolean, Byte, Char, Decimal, Double, and Integer data types.

The following code snippet creates a BinaryWriter and writes string, Boolean, integer, and double data types to the stream. 

string authorName = "Mahesh Chand";  
int age = 30;  
string bookTitle = "ADO.NET Programming using C#";  
bool mvp = true;  
double price = 54.99;  
  
using (BinaryWriter binWriter =  
    new BinaryWriter(File.Open(fileName, FileMode.Create)))  
{  
    // Write string   
    binWriter.Write(authorName);  
    // Write string   
    // Write integer  
    binWriter.Write(age);  
    binWriter.Write(bookTitle);  
    // Write boolean  
    binWriter.Write(mvp);  
    // Write double   
    binWriter.Write(price);  
}  

Complete Code Example

Here is a complete sample code example that creates a binary file and adds data to the file. 

public class BinaryReadWriteClass  
{  
    public void WriteBinary()  
    {  
        try  
        {  
            Console.WriteLine("Binary Writer");  
            string authorName = "Mahesh Chand";  
            int age = 30;  
            string bookTitle = "ADO.NET Programming using C#";  
            bool mvp = true;  
            double price = 54.99;  
  
            string fileName = @"C:\temp\MC.bin";                  
            BinaryWriter bwStream = new BinaryWriter(new FileStream(fileName,FileMode.Create));  
  
            Encoding ascii = Encoding.ASCII;  
            BinaryWriter bwEncoder = new BinaryWriter(new FileStream(fileName, FileMode.Create), ascii);  
  
            using (BinaryWriter binWriter =  
                new BinaryWriter(File.Open(fileName, FileMode.Create)))  
            {  
                // Write string   
                binWriter.Write(authorName);  
                // Write string   
                // Write integer  
                binWriter.Write(age);  
                binWriter.Write(bookTitle);  
                // Write boolean  
                binWriter.Write(mvp);  
                // Write double   
                binWriter.Write(price);  
            }                
            Console.WriteLine("Data Written!");  
            Console.WriteLine();  
        }  
        catch (IOException ioexp)  
        {  
            Console.WriteLine("Error: {0}", ioexp.Message);  
        }  
    }  
}

Summary

This code example demonstrated how to create a binary file in C#.