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BinaryReader.ReadDouble Method

Reads an 8-byte floating point value from the current stream and advances the current position of the stream by eight bytes.

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

Public Overridable Function ReadDouble As Double
Dim instance As BinaryReader
Dim returnValue As Double

returnValue = instance.ReadDouble
public double ReadDouble ()
public function ReadDouble () : double
Not applicable.

Return Value

An 8-byte floating point value read from the current stream.

Exception typeCondition


The end of the stream is reached.


The stream is closed.


An I/O error occurs.

BinaryReader does not restore the file position after an unsuccessful read.

BinaryReader reads this data type in little-endian format.

For a list of common I/O tasks, see Common I/O Tasks.

The following code example shows how to read and write Double data to memory by using the BinaryReader and BinaryWriter classes on top of the MemoryStream class. MemoryStream only reads and writes Byte data.

Imports System
Imports System.IO

Public Class BinaryRW

    Shared Sub Main()
        Dim i As Integer
        Const upperBound As Integer = 1000

        ' Create random data to write to the stream.
        Dim dataArray(upperBound) As Double
        Dim randomGenerator As New Random()
        For i = 0 To upperBound
            dataArray(i) = 100.1 * randomGenerator.NextDouble()
        Next i

        Dim binWriter As New BinaryWriter(New MemoryStream())

            ' Write data to the stream.
            Console.WriteLine("Writing data to the stream.")
            For i = 0 To upperBound
            Next i

            ' Create a reader using the stream from the writer.
            Dim binReader As New BinaryReader(binWriter.BaseStream)

            ' Return to the beginning of the stream.
            binReader.BaseStream.Position = 0

            ' Read and verify the data.
                Console.WriteLine("Verifying the written data.")
                For i = 0 To upperBound
                    If binReader.ReadDouble() <> dataArray(i) Then
                        Console.WriteLine("Error writing data.")
                        Exit For
                    End If
                Next i
                Console.WriteLine("The data was written and verified.")
            Catch ex As EndOfStreamException
                Console.WriteLine("Error writing data: {0}.", _
            End Try
        End Try

    End Sub
End Class

import System.*;
import System.IO.*;

class BinaryRW
    public static void main(String[] args)
        int i;
        final int arrayLength = 1000;

        // Create random data to write to the stream.
        Random randomGenerator = new Random();
        double dataArray[] = new double[arrayLength];
        for(i = 0;i < arrayLength;i++) {
            dataArray[i] = 100.1*randomGenerator.NextDouble() ;
        BinaryWriter binWriter = new BinaryWriter(new MemoryStream());
        try {
            // Write the data to the stream.
            Console.WriteLine("Writing data to the stream.");
            for(i = 0;i < arrayLength;i++)    {
                binWriter.Write(dataArray [ i]);
            // Create a reader using the stream from the writer.
            BinaryReader binReader = 
                new BinaryReader(binWriter.get_BaseStream());
            try {
                try {
                    // Return to the beginning of the stream.

                    // Read and verify the data.
                    Console.WriteLine("Verifying the written data.");
                    for(i = 0;i < arrayLength;i++) {
                        if ( binReader.ReadDouble() != dataArray[i] ) {
                            Console.WriteLine("Error writing data.");
                    Console.WriteLine(("The data was written "
                        + "and verified."));
                catch(EndOfStreamException e) {
                    Console.WriteLine("Error writing data: {0}.",
            finally {
                if (binReader != null) {
                    binReader = null;
        finally {
            if (binWriter != null) {
                binWriter = null;
    } //main
} //BinaryRW

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0