C# Discussion Boards - CodeProject

21-Jul-11 4:12

So far this appears to have stumped a lot of folks, including myself.

The function in Delphi works correctly, the function in C# is crashing with managed/unmanaged errors.

using a delphi.pas generated mrdsio.dll file, the Receive(Adr,Len) is sent on to the mrdsio.dll for processing (mrdsio.dll sends and retrieves data to an mcu epprom memory bank with Adr as Address and Len as Length)

The Tdata (single dimension byte array) is returned from the mrdsio.dll and processed as Data.

Again, Delphi code works, C# fails.

any clues?

original Delphi Code:

type<br />
  TData = array [0..255] of byte;<br />
<br />
function Receive(Adr, Len: integer): TData; stdcall; external 'mrdsio.dll';<br />
<br />
procedure TForm1.Button5Click(Sender: TObject);<br />
var Data: TData;<br />
    i: integer;<br />
    s: string;<br />
begin<br />
if not (CheckBox1.Checked) then<br />
  begin StatusBar1.SimpleText:='Bidirectional operation not allowed'; exit; end;<br />
for i:=0 to 255 do Data[i]:=0;<br />
Data:=Receive($02,8);<br />
if (Data[1]=0) then<br />
  begin StatusBar1.SimpleText:='Failed, check Connection'; exit; end;<br />
s:='';<br />
for i:=1 to 8 do<br />
  s:=s+Chr(Data[i+1]);<br />
Edit1.Text:=s;<br />
end;

Converted C# code;

[DllImport("mrdsio.dll", EntryPoint="Receive", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Ansi)]<br />
public static extern byte[] Receive(int Adr,int Len);<br />
<br />
private void btnRX_Click(object sender, EventArgs e)<br />
           {<br />
            byte[] Data = new byte[256];<br />
            int i;<br />
            string s;<br />
            int Adr = 0x02;<br />
            int Len = 8;<br />
            for (i = 0; i <= 255; i++) Data[i] = 0;<br />
                Data = DLL.Receive(Adr, Len);<br />
            s = " ";<br />
            for (i = 1; i <= 8; i++)<br />
                s = s + Data[i + 1].ToString();<br />
            txtBox1.Text = s;<br />
           }<br />

Richard MacCutchan21-Jul-11 4:38

Richard MacCutchan

21-Jul-11 4:38

Aurbo7 wrote:
crashing with managed/unmanaged errors.

Unless you show the exact text of these errors any suggestions will be pure guesswork.

The best things in life are not things.

Aurbo721-Jul-11 4:49

21-Jul-11 4:49

MarshalDirectiveException was unhandled<br />
<br />
Cannot marshal 'return value' Invalid managed/unmanaged type combination.

Richard MacCutchan21-Jul-11 6:34

Richard MacCutchan

21-Jul-11 6:34

Your unmanaged code returns a pointer to an array, but your managed code has not been told how to marshall the data. I'm not an expert in this interface but you need to add some more attributes to tell the marshalling code that a pointer is being passed back. You can find more information here[^].

The best things in life are not things.

DaveyM6921-Jul-11 7:48

DaveyM69

21-Jul-11 7:48

If Richard is correct and it's returning a pointer then you may need to copy the data at the pointer to a managed byte array.

byte[] data = new byte[256];
// ...
IntPtr result = DLL.Receive(Adr, Len);
// ...
Marshal.Copy(result, data, 0, 256);

[DllImport("mrdsio.dll", EntryPoint="Receive", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Ansi)]
public static extern IntPtr Receive(int Adr,int Len);

Aurbo721-Jul-11 8:09

21-Jul-11 8:09

Dave,

your version offers up a different error,

'AcessViolationException was unhandled'

Attempted to read or write protected memory.

DaveyM6921-Jul-11 9:30

DaveyM69

21-Jul-11 9:30

OK, I'm a little confused as I'm not familiar with Delphi.

Does the function return a single byte, a pointer or a byte array? That it loops 256 times indicates it may be just a byte that is returned which needs to be added to a separate byte array?

Aurbo721-Jul-11 10:30

21-Jul-11 10:30

Tdata returns an entire single dimension byte array.

Adr is the memory address, in this instance eeprom memory address: 0x02

Len is the length of the data bytes[8]

256 was just the standard number for an array declaration, In all reality and practicality

byte[] Data = new byte[256];

could just be

byte[] Data = new byte[8]

The byte[8] is then run through the for i=.... loop to convert the array from bytes to string.

BobJanova22-Jul-11 2:32

BobJanova

22-Jul-11 2:32

This assumes that the result actually is 256 bytes. I suspect that

Marshal.Copy(result, data, 0, len);

might actually be what is wanted here.

The original code seems poorly written, Data is initialised and then assigned to, making the initialisation step pointless.

BobJanova22-Jul-11 2:31

BobJanova

22-Jul-11 2:31

The error is on 'DLL.Receive' I assume?

What is the actual declaration of the target function in C? I suspect that Delphi is marshalling the result type automatically in some way and C# is not doing the same thing, and the result type isn't actually byte[] (it is probably byte*). Marshalling pointer types requires a bit more work in .Net.

Aurbo722-Jul-11 4:45

crystal reports running total problem.

22-Jul-11 4:45

Correct, Error occurs at Receive(Adr,Len)

The Delphi version as posted in the original entry, works fine with the Delphi example.exe calling the Delphi.dll. There is a Send(Data[],Len) routine as well that works fine in both Delphi and its converted C# version.

I have not explored the byte* route yet, perhaps it may offer a solution.

Asif Rehman21-Jul-11 3:27

Asif Rehman

21-Jul-11 3:27

I'm having procedure with following fields e.g.(Previous.Balance, Debit, Credit )

Now in crystal reports. I want report structure like an account statement e.g. bank statement.

Description Dr Cr. Balance
Opening.. prevBalance
transaction 1 10000 prevBalance+Dr-Cr
transaction 2 5000 upperBalance+Dr-Cr
transaction 3 5000 upperBalance+Dr-Cr

How to achieve this type of running total in crystal reports in VS2010.

Regards.
Asif Rehman

What is best for Parent Child List

Anubhava Dimri20-Jul-11 23:38

Anubhava Dimri

20-Jul-11 23:38

Hello Everybody,

I want to create a List for Parent Child Information. So I want to know that what is the best Object for Store Information of Parent Child.

I am confused with :

Arraylist, IList,List,Distionery or
else in your mind.

If you have any example then your most welcome to share your knoledge.

Thanks

If you can think then I Can.

#realJSOP21-Jul-11 0:16

#realJSOP

21-Jul-11 0:16

A List.

".45 ACP - because shooting twice is just silly" - JSOP, 2010
-----
You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass." - Dale Earnhardt, 1997

Anubhava Dimri22-Jul-11 0:16

Anubhava Dimri

22-Jul-11 0:16

Hello John,

Thanks for your suggession. Can u please help me How Can i Create a class that contain the information of Parant and Childs.

Thanks

If you can think then I Can.

OriginalGriff21-Jul-11 2:09

OriginalGriff

21-Jul-11 2:09

As JSOP says, a List is probably the best.
However, there is the TreeNode class[^] which is used as part of teh TreeView class - this is already configured with Parent and Nodes properties, so it may be worth investigating.
If nothing else, they are easy to display - just add them into a TreeView...

Real men don't use instructions. They are only the manufacturers opinion on how to put the thing together.

Manfred R. Bihy: "Looks as if OP is learning resistant."