BinaryReader.ReadChars(Int32) Method

Reference

Definition

Namespace:: System.IO

Assembly:: System.IO.dll

Assembly:: System.Runtime.dll

Assembly:: System.Runtime.Extensions.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: BinaryReader.cs

Source:: BinaryReader.cs

Source:: BinaryReader.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Reads the specified number of characters from the current stream, returns the data in a character array, and advances the current position in accordance with the Encoding used and the specific character being read from the stream.

public:
 virtual cli::array <char> ^ ReadChars(int count);

public virtual char[] ReadChars (int count);

abstract member ReadChars : int -> char[]
override this.ReadChars : int -> char[]

Public Overridable Function ReadChars (count As Integer) As Char()

Parameters

count: Int32

The number of characters to read.

Returns

Char[]

A character array containing data read from the underlying stream. This might be less than the number of characters requested if the end of the stream is reached.

Exceptions

ArgumentException

The number of decoded characters to read is greater than count. This can happen if a Unicode decoder returns fallback characters or a surrogate pair.

ObjectDisposedException

The stream is closed.

IOException

An I/O error occurred.

ArgumentOutOfRangeException

count is negative.

Examples

The following code example shows how to read and write data using memory as a backing store.

using namespace System;
using namespace System::IO;
int main()
{
   array<Char>^invalidPathChars = Path::InvalidPathChars;
   MemoryStream^ memStream = gcnew MemoryStream;
   BinaryWriter^ binWriter = gcnew BinaryWriter( memStream );
   
   // Write to memory.
   binWriter->Write( "Invalid file path characters are: " );
   binWriter->Write( Path::InvalidPathChars );
   
   // Create the reader using the same MemoryStream 
   // as used with the writer.
   BinaryReader^ binReader = gcnew BinaryReader( memStream );
   
   // Set Position to the beginning of the stream.
   binReader->BaseStream->Position = 0;
   
   // Read the data from memory and write it to the console.
   Console::Write( binReader->ReadString() );
   Console::WriteLine( binReader->ReadChars( (int)(memStream->Length - memStream->Position) ) );
}

using System;
using System.IO;

class BinaryRW
{
    static void Main()
    {
        char[] invalidPathChars = Path.InvalidPathChars;
        MemoryStream memStream = new MemoryStream();
        BinaryWriter binWriter = new BinaryWriter(memStream);

        // Write to memory.
        binWriter.Write("Invalid file path characters are: ");
        binWriter.Write(Path.InvalidPathChars);

        // Create the reader using the same MemoryStream
        // as used with the writer.
        BinaryReader binReader = new BinaryReader(memStream);

        // Set Position to the beginning of the stream.
        memStream.Position = 0;

        // Read the data from memory and write it to the console.
        Console.Write(binReader.ReadString());
        Console.WriteLine(binReader.ReadChars(
            (int)(memStream.Length - memStream.Position)));
    }
}

open System.IO

let invalidPathChars = Path.GetInvalidPathChars()
let memStream = new MemoryStream()
let binWriter = new BinaryWriter(memStream)

// Write to memory.
binWriter.Write "Invalid file path characters are: "
binWriter.Write invalidPathChars

// Create the reader using the same MemoryStream
// as used with the writer.
let binReader = new BinaryReader(memStream)

// Set Position to the beginning of the stream.
memStream.Position <- 0

// Read the data from memory and write it to the console.
printf $"{binReader.ReadString()}"
printfn $"{binReader.ReadChars(int (memStream.Length - memStream.Position))}"

Imports System.IO

Public Class BinaryRW

    Shared Sub Main()
    
        Dim invalidPathChars() As Char = Path.InvalidPathChars
        Dim memStream As new MemoryStream()
        Dim binWriter As New BinaryWriter(memStream)

        ' Write to memory.
        binWriter.Write("Invalid file path characters are: ")
        binWriter.Write(Path.InvalidPathChars)

        ' Create the reader using the same MemoryStream 
        ' as used with the writer.
        Dim binReader As New BinaryReader(memStream)

        ' Set Position to the beginning of the stream.
        memStream.Position = 0

        ' Read the data from memory and write it to the console.
        Console.Write(binReader.ReadString())
        Console.WriteLine(binReader.ReadChars( _
            CInt(memStream.Length - memStream.Position)))
    
    End Sub
End Class

Remarks

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

When reading from network streams, in some rare cases, the ReadChars method might read an extra character from the stream if the BinaryReader was constructed with Unicode encoding. If this occurs, you can use the ReadBytes method to read a fixed-length byte array, and then pass that array to the ReadChars method.

Applies to

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