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EndRead  
Method  
Wait for an asynchronous read to complete
FileStream Class
System.IO NameSpace
CF1.  Function EndRead ( AsyncResult : IAsyncResult ) : Integer;
CF : Methods with this mark are Compact Framework Compatible
Description
Normally, you would allow the callback method of an asynchronous read to be called. If you need to wait until this happens in the main thread of operation, then call EndRead.
 
The AsynResult parameter should be supplied with the value returned by the BeginRead you want to wait for.
 
It will return the number of bytes read, unless the stream end was reached.
Microsoft MSDN Links
System.IO
System.IO.FileStream
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A simple example
program Project1;
{$APPTYPE CONSOLE}

uses
  System.IO,
  System.Runtime.Remoting.Messaging;

var
  Stream    : System.IO.FileStream;
  ByteArray : Array of Byte;
  AsyncRes  : IAsyncResult;
  Index     : Integer;

procedure ReadDone(AsyncResult : IAsyncResult);
var
  Index : Integer;
begin
  Console.WriteLine('Read is finished :');
  Console.WriteLine;

  // Display our array contents
  for Index := 0 to Length(ByteArray)-1 do
    Console.WriteLine(ByteArray[Index].ToString);
end;

begin
  // Create our File Stream
  Stream := System.IO.FileStream.Create('C:\DelphiBasics.txt', FileMode.Create);

  // Write to the stream
  Stream.WriteByte(1);
  Stream.WriteByte(2);
  Stream.WriteByte(3);
  Stream.WriteByte(4);
  Stream.WriteByte(5);
  Stream.WriteByte(6);
  Stream.WriteByte(7);
  Stream.WriteByte(8);
  Stream.WriteByte(9);

  // Move to the start of the stream
  Stream.Seek(0, SeekOrigin.Begin);

  // Declare our array to hold the returned data
  SetLength(ByteArray, 12);

  // Read from the stream asynchronously
  AsyncRes := Stream.BeginRead(ByteArray, 0, 10, ReadDone, TObject.Create);

  // Wait for the read to end
  Console.WriteLine;
  Console.WriteLine('Waiting in main thread for read to complete');
  Console.WriteLine;

  Stream.EndRead(AsyncRes);

  // Display our array contents
  for Index := 0 to Length(ByteArray)-1 do
    Console.WriteLine(ByteArray[Index].ToString);

  // Close the file stream
  Stream.Close;

  Console.Readline;
end.
   Read is finished :
  
   1
   2
   3
   4
   5
   6
   7
   8
   9
   0
   0
   0
  
   Waiting in main thread for read to complete
  
   1
   2
   3
   4
   5
   6
   7
   8
   9
   0
   0
   0
 
 
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