How can i get an object from pointer-address

Question

i have written a user control for WinCC (Siemens) (SCADA). Now I want to pass a pointer to the control. The only way to do this is: write the pointer to a property.

WinCC has only this methods to set properties

• SetPropBOOL
• SetPropChar
• SetPropDouble
• SetPropWord

The property from control has UInt as datatype and i use the SetPropDouble method to set the address from an object.

WinCC Global Script (ANSI-C)

//autoDB is an ADODB.Connection object
//object* autoDB = __object_create("ADODB.Connection");
extern __object* autoDB;
//SetPropDouble( "PictureName", "ControlName", "PropertyName", (DWORD)(&autoDB) );
SetPropDouble( "PictureName", "ControlName", "PropertyName", (DWORD)autoDB );

I've debug my control (hook on WinCC-process) and i see the property-set becomes assigned an address-value e.g. 0x03041080.

Now the question: How can i get the object in c# (.Net) on the address?

My try throws an exception: ExecutionEngineException

private ADODB.Connection _database;
private IntPtr _ptr = IntPtr.Zero;

public uint DataBase{
    get{
        return (uint)_ptr;
    }
    set{
        if( value != 0 ){
            _ptr = (IntPtr)value;
            GCHandle gH = GCHandle.FromIntPtr(_ptr); // THIS LINE THROW THE EXCEPTION
            _database = gH.Target;
        }
    }
}

---

Ok: i've changed my code to use STRING

WinCC

extern __object* autoDB;
DWORD addr = (DWORD)autoDB;
char sAddr[11];
sprintf( sAddr, "%d\0", addr );
SetPropChar( "PictureName", "ControlName", "DataBaseAddr", sAddr );

And c# is now

private string _lpszDataBaseAddr = "";
public string DataBaseAddr{
    get{
        return _lpszDataBaseAddr;
    }
    set{
        uint addr;
        bool ret = uint.TryParse( value, out addr );
        if( ! ret ){
            return;
        }
        IntPtr ptr = (IntPtr)addr;
        GCHandle gH = GCHandle.FromIntPtr( ptr );  // THE SAME ERROR!
    }
}

---

Other findings!

The address from the ADO-Object is not in the process-memory who called my control (debug with ollydbg). WinCC has two programs: PDLRT.exe for visualisation (this is calling my control) and SCRIPT.exe for running GLOBAL-SCRIPT (Ansi-C).

From PDLRT, i've access to the pointer-address from ADO-Object. By call GCHandle in C# of the ADO-object-address, the exception is thrown. (ExecutionEngineException)

Answer 1

Ok,

long time ago and I've ask the support from Siemens.

Siemens: The loaded Dlls, Controls and so on are load in an separated memory and not in the application (main) memory. Memory-Address-Share between Dlls, Controls .... is not working. All have a separated memory.

Super. Only way: Pipes or other communication implementations (TCP/IP, ...).

Answer 2

I have no idea if C# can access through a pointer into C++ like that.

Regardless, this: (DWORD)(&autoDB) is wrong, that puts the address of the pointer as the property's value, which is pointless.

You need the pointer's value, i.e. (DWORD) autoDB.

Also, SetPropDouble() accepts a value of type double, i.e. a floating-point number. That will not be a very nice way to share a pointer, which is a (large) integer. Try some different representation, string might work if you don't have access to a large enough integer.