Questions about c # type turn to Delphi-CodePudding

The following is a function of c # prototype:
Int GetDevData (IntPtr h, ref byte buffer, int buffersize, string tablename, string filename, the string filter, string options);
I want to switch to Delphi function is as follows:
The function GetDevData (h: integer; Var Buffer: an array of byte;
BufferSize: integer; Tablename: string;
Filename: the string; The Filter: string; Options: string) : integer;

Specific calling code is as follows:

 
Var 
Buffer: an array of byte; 
Buffersize: integer; 
Ret: integer; 
The begin 
. 

Buffersize:=1024 * 1024; 
Setlength (buffer, buffersize); 

//execution to the following function was illegal access memory mistake 
Ret:=GetDeData (h, Buffer, buffersize, tablename, filename, the filter, the options). 

. 
end;

I think may be the ref byte buffer into the var buffer: an array of byte in a bit of a problem, ask about how to convert and how to use this type?