Read Method

MemoryStream.Read Method (Byte[], Int32, Int32)


Reads a block of bytes from the current stream and writes the data to a buffer.

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

public override int Read(
	byte[] buffer,
	int offset,
	int count


Type: System.Byte[]

When this method returns, contains the specified byte array with the values between offset and (offset + count - 1) replaced by the characters read from the current stream.

Type: System.Int32

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

Type: System.Int32

The maximum number of bytes to read.

Return Value

Type: System.Int32

The total number of bytes written into the buffer. This can be less than the number of bytes requested if that number of bytes are not currently available, or zero if the end of the stream is reached before any bytes are read.

Exception Condition

buffer is null.


offset or count is negative.


offset subtracted from the buffer length is less than count.


The current stream instance is closed.

This method overrides Read.

The offset parameter gives the offset of the first byte in buffer to which data from the current stream is written. The count parameter gives the maximum number of bytes to read from the current stream. The returned value is the actual number of bytes read, or zero if the end of the stream is reached.

If the read operation is successful, the current position within the stream advances by the number of bytes read. If an exception occurs, the current position within the stream remains unchanged.

The Read method will return zero only if the end of the stream is reached. In all other cases, Read always reads at least one byte from the stream before returning. By definition, if no data is available from the stream upon a call to Read, the Read method returns zero (the end of the stream is reached automatically). 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.


If the byte array specified in the buffer parameter is the underlying buffer returned by the GetBuffer method, the array contents are overwritten, and no exception is thrown.

This code example is part of a larger example provided for the MemoryStream class.

// Read the first 20 bytes from the stream.
byteArray = new byte[memStream.Length];
count = memStream.Read(byteArray, 0, 20);

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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