Problem reading TMemoryStream to a local Variable

[44617665]

Hi

I have a problem reading data from a TMemoryStream object into a local variable, When I call 'ReadBuffer' the call stack is corrupted and my code throws an Exception when I reach the end of the procedure. Reading the Stream into a class member variable works fine but I'd like some help understanding why this fails when using a local variable. As an example of this if I have a form with 2 Edit boxes and a button and the following code under the button click

procedure TForm1.Button1Click(Sender: TObject);
var
  ms : TMemoryStream;
  S : String;
  //S2 : String;
  B : array of Byte;
  I : Integer;
begin
  S := Edit1.Text;
  I := Length(S);
  SetLength(B,I);
  ms := TMemoryStream.Create;
  try

  Move(S[1],B[0],I);

  I := Length(B);
  ms.WriteBuffer(B,I);

  ms.Seek(0, soFromBeginning);
  ms.ReadBuffer(S2,I);
  Edit2.Text := S2;
  finally
    ms.Free;
    SetLength(B,0);
  end;

end;

if S2 above is set to be a class variable then this works as I'd expect and copies the contents from Edit1 to Edit2, however if S2 is a local variable then this fails and throws an exception?

Any suggestions to a better solution than having to declare class member variables?

Many thanks

 

[whosrdaddy]

it should be ms.ReadBuffer(S2[1],I);


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[44617665]

Thanks whosrdaddy

Also neeeded to change the ms.writeBuffer to pass in first Element of the byte array but this works.