How to: Read and Write to a Newly Created Data File

The BinaryWriter and BinaryReader classes are used for writing and reading data rather than character strings. The following example demonstrates how to write data to, and read data from, a new, empty file stream called Test.data. After creating the data file in the current directory, the associated BinaryWriter and BinaryReader objects are created, and the BinaryWriter object is used to write the integers 0 through 10 to Test.data, which leaves the file pointer at the end of the file. After setting the file pointer back to the origin, the BinaryReader object reads out the specified content.

Example

using namespace System;
using namespace System::IO;

ref class MyStream
{
private:
    static String^ FILE_NAME = "Test.data";

public:
    static void Main()
    {
        // Create the new, empty data file.
        if (File::Exists(FILE_NAME))
        {
            Console::WriteLine("{0} already exists!", FILE_NAME);
            return;
        }
        FileStream^ fs = gcnew FileStream(FILE_NAME, FileMode::CreateNew);
        // Create the writer for data.
        BinaryWriter^ w = gcnew BinaryWriter(fs);
        // Write data to Test.data.
        for (int i = 0; i < 11; i++)
        {
            w->Write(i);
        }
        w->Close();
        fs->Close();
        // Create the reader for data.
        fs = gcnew FileStream(FILE_NAME, FileMode::Open, FileAccess::Read);
        BinaryReader^ r = gcnew BinaryReader(fs);
        // Read data from Test.data.
        for (int i = 0; i < 11; i++)
        {
            Console::WriteLine(r->ReadInt32());
        }
        fs->Close();
    }
};

int main()
{
    MyStream::Main();
}
using System;
using System.IO;

class MyStream
{
    private const string FILE_NAME = "Test.data";

    public static void Main()
    {
        if (File.Exists(FILE_NAME))
        {
            Console.WriteLine("{0} already exists!", FILE_NAME);
            return;
        }

        using (FileStream fs = new FileStream(FILE_NAME, FileMode.CreateNew))
        {
            using (BinaryWriter w = new BinaryWriter(fs))
            {
                for (int i = 0; i < 11; i++)
                {
                    w.Write(i);
                }
            }
        }
        
        using (FileStream fs = new FileStream(FILE_NAME, FileMode.Open, FileAccess.Read))
        {
            using (BinaryReader r = new BinaryReader(fs))
            {
                for (int i = 0; i < 11; i++)
                {
                    Console.WriteLine(r.ReadInt32());
                }
            }
        }
    }
}
Imports System
Imports System.IO

Class MyStream
    Private Const FILE_NAME As String = "Test.data"

    Public Shared Sub Main()
        If File.Exists(FILE_NAME) Then
            Console.WriteLine("{0} already exists!", FILE_NAME)
            Return
        End If

        Using fs As New FileStream(FILE_NAME, FileMode.CreateNew)
            Using w As New BinaryWriter(fs)
                For i As Integer = 0 To 10
                    w.Write(i)
                Next
            End Using
        End Using

        Using fs As New FileStream(FILE_NAME, FileMode.Open, FileAccess.Read)
            Using r As New BinaryReader(fs)
                For i As Integer = 0 To 10
                    Console.WriteLine(r.ReadInt32())
                Next
            End Using
        End Using
    End Sub
End Class

Robust Programming

If Test.data already exists in the current directory, an IOException exception is thrown. Use the file mode option FileMode.Create when you initialize the file stream to always create a new file without throwing an exception.

See Also

BinaryReader
BinaryWriter
FileStream
FileStream.Seek
SeekOrigin
How to: Enumerate Directories and Files
How to: Open and Append to a Log File
How to: Read Text from a File
How to: Write Text to a File
How to: Read Characters from a String
How to: Write Characters to a String
File and Stream I-O