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Stream.Read Method

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Definition

Namespace:
System.IO
Assembly:
System.Runtime.dll
Assembly:
netstandard.dll
Assembly:
System.IO.dll
Assembly:
mscorlib.dll

Overloads

Read(Span<Byte>)

When overridden in a derived class, reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read.
Read(Byte[], Int32, Int32)

When overridden in a derived class, reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read.

Read(Span<Byte>)

Source:
Stream.cs
Source:
Stream.cs
Source:
Stream.cs

When overridden in a derived class, reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read.

public:
 virtual int Read(Span<System::Byte> buffer);
public virtual int Read (Span<byte> buffer);
abstract member Read : Span<byte> -> int
override this.Read : Span<byte> -> int
Public Overridable Function Read (buffer As Span(Of Byte)) As Integer

Parameters

buffer
Span<Byte>

A region of memory. When this method returns, the contents of this region are replaced by the bytes read from the current source.

Returns

Int32

The total number of bytes read into the buffer. This can be less than the size of the buffer if that many bytes are not currently available, or zero (0) if the buffer's length is zero or the end of the stream has been reached.

Remarks

Use the CanRead property to determine whether the current instance supports reading. Use the ReadAsync method to read asynchronously from the current stream.

Implementations of this method read a maximum of buffer.Length bytes from the current stream and store them in buffer. The current position within the stream is advanced by the number of bytes read; however, if an exception occurs, the current position within the stream remains unchanged. Implementations return the number of bytes read. If more than zero bytes are requested, the implementation will not complete the operation until at least one byte of data can be read (if zero bytes were requested, some implementations may similarly not complete until at least one byte is available, but no data will be consumed from the stream in such a case). Read returns 0 only if zero bytes were requested or when there is no more data in the stream and no more is expected (such as a closed socket or end of file). An implementation is free to return fewer bytes than requested even if the end of the stream has not been reached.

Use BinaryReader for reading primitive data types.

Applies to

Read(Byte[], Int32, Int32)

Source:
Stream.cs
Source:
Stream.cs
Source:
Stream.cs

When overridden in a derived class, reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read.

public:
 abstract int Read(cli::array <System::Byte> ^ buffer, int offset, int count);
public abstract int Read (byte[] buffer, int offset, int count);
abstract member Read : byte[] * int * int -> int
Public MustOverride Function Read (buffer As Byte(), offset As Integer, count As Integer) As Integer

Parameters

buffer
Byte[]

An array of bytes. When this method returns, the buffer contains the specified byte array with the values between offset and (offset + count - 1) replaced by the bytes read from the current source.

offset
Int32

The zero-based byte offset in buffer at which to begin storing the data read from the current stream.

count
Int32

The maximum number of bytes to be read from the current stream.

Returns

Int32

The total number of bytes read into the buffer. This can be less than the number of bytes requested if that many bytes are not currently available, or zero (0) if count is 0 or the end of the stream has been reached.

Exceptions

ArgumentException

The sum of offset and count is larger than the buffer length.

ArgumentNullException

buffer is null.

ArgumentOutOfRangeException

offset or count is negative.

IOException

An I/O error occurs.

NotSupportedException

The stream does not support reading.

ObjectDisposedException

Methods were called after the stream was closed.

Examples

The following example shows how to use Read to read a block of data.

using namespace System;
using namespace System::IO;

public ref class Block
{
public:
    static void Main()
    {
        Stream^ s = gcnew MemoryStream();
        for (int i = 0; i < 100; i++)
        {
            s->WriteByte((Byte)i);
        }
        s->Position = 0;

        // Now read s into a byte buffer.
        array<Byte>^ bytes = gcnew array<Byte>(s->Length);
        int numBytesToRead = (int) s->Length;
        int numBytesRead = 0;
        while (numBytesToRead > 0)
        {
            // Read may return anything from 0 to 10.
            int n = s->Read(bytes, numBytesRead, 10);
            // The end of the file is reached.
            if (n == 0)
            {
                break;
            }
            numBytesRead += n;
            numBytesToRead -= n;
        }
        s->Close();
        // numBytesToRead should be 0 now, and numBytesRead should
        // equal 100.
        Console::WriteLine("number of bytes read: {0:d}", numBytesRead);
    }
};

int main()
{
    Block::Main();
}

using System;
using System.IO;

public class Block
{
    public static void Main()
    {
        Stream s = new MemoryStream();
        for (int i = 0; i < 122; i++)
        {
            s.WriteByte((byte)i);
        }
        s.Position = 0;

        // Now read s into a byte buffer with a little padding.
        byte[] bytes = new byte[s.Length + 10];
        int numBytesToRead = (int)s.Length;
        int numBytesRead = 0;
        do
        {
            // Read may return anything from 0 to 10.
            int n = s.Read(bytes, numBytesRead, 10);
            numBytesRead += n;
            numBytesToRead -= n;
        } while (numBytesToRead > 0);
        s.Close();

        Console.WriteLine("number of bytes read: {0:d}", numBytesRead);
    }
}

Imports System.IO

Public Class Block
    Public Shared Sub Main()
        Dim s As Stream = New MemoryStream()
        For i As Integer = 0 To 121
            s.WriteByte(CType(i, Byte))
        Next i
        s.Position = 0

        ' Now read s into a byte buffer that is padded slightly.
        Dim bytes(s.Length + 10) As Byte
        Dim numBytesToRead As Integer = s.Length
        Dim numBytesRead As Integer = 0
        Dim n As Integer
        Do
            ' Read may return anything from 0 to 10.
            n = s.Read(bytes, numBytesRead, 10)
            ' The end of the file is reached.
            numBytesRead += n
            numBytesToRead -= n
        Loop While numBytesToRead > 0

        s.Close()
    
        Console.WriteLine("number of bytes read: {0:d}", numBytesRead)
    End Sub
End Class

Remarks

Use the CanRead property to determine whether the current instance supports reading. Use the ReadAsync method to read asynchronously from the current stream.

Implementations of this method read a maximum of count bytes from the current stream and store them in buffer beginning at offset. The current position within the stream is advanced by the number of bytes read; however, if an exception occurs, the current position within the stream remains unchanged. Implementations return the number of bytes read. If more than zero bytes are requested, the implementation will not complete the operation until at least one byte of data can be read (some implementations may similarly not complete until at least one byte is available even if zero bytes were requested, but no data will be consumed from the stream in such a case). Read returns 0 only if zero bytes were requested or when there is no more data in the stream and no more is expected (such as a closed socket or end of file). An implementation is free to return fewer bytes than requested even if the end of the stream has not been reached.

Use BinaryReader for reading primitive data types.

See also

Applies to