Asp Forum - Cannot marshal 'return value' - microsoft.public.dotnet.framework.interop

ShaunO

5/14/2007 7:26:00 AM

Hi,
I am trying to call an old Delphi .dll

// DELPHI definition (should return an array of 256 chars)
function DiskSaveFooter(missionname,qlffilename,id:pchar):TCharArray; export;

// My C# definition
[DllImport("qn.dll",
CharSet=CharSet.Ansi,CallingConvention=CallingConvention.StdCall)]

public static extern char[] DiskSaveFooter(string missionname, string
qlffilename, string id);

// My C# Implementation
char []b = new char[256];
b = qn.DiskSaveFooter("mis1", "", "000:000");

I get the ERROR: Cannot marshal 'return value': Invalid managed/unmanaged
type combination.

Any suggestions please?

4 Answers

G Himangi

5/16/2007 5:32:00 AM

It may work if you define the function as

[DllImport("qn.dll",
CharSet=CharSet.Ansi,CallingConvention=CallingConvention.StdCall)]

public static extern IntPtr DiskSaveFooter(string missionname, string
qlffilename, string id);

and then.....

IntPtr ptr = qn.DiskSaveFooter("mis1", "", "000:000");
char* charArray = (char*)ptr;

this requires unsafe code though.

Or you can use Marshal.Copy to copy the contents of the ptr to a char/byte
array.

---------
- G Himangi, Sky Software http://www....
Shell MegaPack : GUI Controls For Drop-In Windows Explorer like Shell
Browsing Functionality For Your App (.Net & ActiveX Editions).
EZNamespaceExtensions.Net : Develop namespace extensions rapidly in .Net
EZShellExtensions.Net : Develop all shell extensions,explorer bars and BHOs
rapidly in .Net
---------

"ShaunO" <ShaunO@discussions.microsoft.com> wrote in message
news:941ABD0B-C05C-4636-A2D9-8F247D252E54@microsoft.com...
> Hi,
> I am trying to call an old Delphi .dll
>
> // DELPHI definition (should return an array of 256 chars)
> function DiskSaveFooter(missionname,qlffilename,id:pchar):TCharArray;
> export;
>
> // My C# definition
> [DllImport("qn.dll",
> CharSet=CharSet.Ansi,CallingConvention=CallingConvention.StdCall)]
>
> public static extern char[] DiskSaveFooter(string missionname, string
> qlffilename, string id);
>
> // My C# Implementation
> char []b = new char[256];
> b = qn.DiskSaveFooter("mis1", "", "000:000");
>
>
> I get the ERROR: Cannot marshal 'return value': Invalid managed/unmanaged
> type combination.
>
> Any suggestions please?

ShaunO

5/16/2007 2:12:00 PM

Thanks for the suggestion.
It errors with
A call to PInvoke function 'DLLTest!DLLTest.Q::DiskSaveFooter' has
unbalanced the stack. This is likely because the managed PInvoke signature
does not match the unmanaged target signature. Check that the calling
convention and parameters of the PInvoke signature match the target unmanaged
signature.

I get this error message on the
IntPtr ptr = qn.DiskSaveFooter("mis1", "", "000:000"); line.

I think that Delphi's native strings are single-byte strings, whereas
..NET's are UTF-16 which may be affecting things but i get the above error
message when i define the return type as anything other than char[]

Does this help?

"G Himangi" wrote:

> It may work if you define the function as
>
> [DllImport("qn.dll",
> CharSet=CharSet.Ansi,CallingConvention=CallingConvention.StdCall)]
>
> public static extern IntPtr DiskSaveFooter(string missionname, string
> qlffilename, string id);
>
> and then.....
>
> IntPtr ptr = qn.DiskSaveFooter("mis1", "", "000:000");
> char* charArray = (char*)ptr;
>
> this requires unsafe code though.
>
> Or you can use Marshal.Copy to copy the contents of the ptr to a char/byte
> array.
>
> ---------
> - G Himangi, Sky Software http://www....
> Shell MegaPack : GUI Controls For Drop-In Windows Explorer like Shell
> Browsing Functionality For Your App (.Net & ActiveX Editions).
> EZNamespaceExtensions.Net : Develop namespace extensions rapidly in .Net
> EZShellExtensions.Net : Develop all shell extensions,explorer bars and BHOs
> rapidly in .Net
> ---------
>
>
>
> "ShaunO" <ShaunO@discussions.microsoft.com> wrote in message
> news:941ABD0B-C05C-4636-A2D9-8F247D252E54@microsoft.com...
> > Hi,
> > I am trying to call an old Delphi .dll
> >
> > // DELPHI definition (should return an array of 256 chars)
> > function DiskSaveFooter(missionname,qlffilename,id:pchar):TCharArray;
> > export;
> >
> > // My C# definition
> > [DllImport("qn.dll",
> > CharSet=CharSet.Ansi,CallingConvention=CallingConvention.StdCall)]
> >
> > public static extern char[] DiskSaveFooter(string missionname, string
> > qlffilename, string id);
> >
> > // My C# Implementation
> > char []b = new char[256];
> > b = qn.DiskSaveFooter("mis1", "", "000:000");
> >
> >
> > I get the ERROR: Cannot marshal 'return value': Invalid managed/unmanaged
> > type combination.
> >
> > Any suggestions please?
>
>
>

G Himangi

5/21/2007 11:54:00 AM

You can try applying a MArshalAs(ByValArray, SIzeConst=260) to the return
type of your method signature and change the return type from char[] to
byte[]

Did that work?

---------
- G Himangi, Sky Software http://www....
Shell MegaPack : GUI Controls For Drop-In Windows Explorer like Shell
Browsing Functionality For Your App (.Net & ActiveX Editions).
EZNamespaceExtensions.Net : Develop namespace extensions rapidly in .Net
EZShellExtensions.Net : Develop all shell extensions,explorer bars and BHOs
rapidly in .Net
---------

"ShaunO" <ShaunO@discussions.microsoft.com> wrote in message
news:7C3D477B-9C16-4011-8373-E88C572F9E7D@microsoft.com...
> Thanks for the suggestion.
> It errors with
> A call to PInvoke function 'DLLTest!DLLTest.Q::DiskSaveFooter' has
> unbalanced the stack. This is likely because the managed PInvoke signature
> does not match the unmanaged target signature. Check that the calling
> convention and parameters of the PInvoke signature match the target
> unmanaged
> signature.
>
> I get this error message on the
> IntPtr ptr = qn.DiskSaveFooter("mis1", "", "000:000"); line.
>
> I think that Delphi's native strings are single-byte strings, whereas
> .NET's are UTF-16 which may be affecting things but i get the above error
> message when i define the return type as anything other than char[]
>
> Does this help?
>
>
>
> "G Himangi" wrote:
>
>> It may work if you define the function as
>>
>> [DllImport("qn.dll",
>> CharSet=CharSet.Ansi,CallingConvention=CallingConvention.StdCall)]
>>
>> public static extern IntPtr DiskSaveFooter(string missionname, string
>> qlffilename, string id);
>>
>> and then.....
>>
>> IntPtr ptr = qn.DiskSaveFooter("mis1", "", "000:000");
>> char* charArray = (char*)ptr;
>>
>> this requires unsafe code though.
>>
>> Or you can use Marshal.Copy to copy the contents of the ptr to a
>> char/byte
>> array.
>>
>> ---------
>> - G Himangi, Sky Software http://www....
>> Shell MegaPack : GUI Controls For Drop-In Windows Explorer like Shell
>> Browsing Functionality For Your App (.Net & ActiveX Editions).
>> EZNamespaceExtensions.Net : Develop namespace extensions rapidly in .Net
>> EZShellExtensions.Net : Develop all shell extensions,explorer bars and
>> BHOs
>> rapidly in .Net
>> ---------
>>
>>
>>
>> "ShaunO" <ShaunO@discussions.microsoft.com> wrote in message
>> news:941ABD0B-C05C-4636-A2D9-8F247D252E54@microsoft.com...
>> > Hi,
>> > I am trying to call an old Delphi .dll
>> >
>> > // DELPHI definition (should return an array of 256 chars)
>> > function DiskSaveFooter(missionname,qlffilename,id:pchar):TCharArray;
>> > export;
>> >
>> > // My C# definition
>> > [DllImport("qn.dll",
>> > CharSet=CharSet.Ansi,CallingConvention=CallingConvention.StdCall)]
>> >
>> > public static extern char[] DiskSaveFooter(string missionname, string
>> > qlffilename, string id);
>> >
>> > // My C# Implementation
>> > char []b = new char[256];
>> > b = qn.DiskSaveFooter("mis1", "", "000:000");
>> >
>> >
>> > I get the ERROR: Cannot marshal 'return value': Invalid
>> > managed/unmanaged
>> > type combination.
>> >
>> > Any suggestions please?
>>
>>
>>

ShaunO

5/21/2007 7:09:00 PM

Thanks but sadly not !
The closest implementation i can do is:

[return: MarshalAs(UnmanagedType.ByValArray, SizeConst = 260)]
public static extern byte[] DiskSaveFooter(string missionname,
string qlffilename, string id);

but this gives a compile error of:
Error emitting 'System.Runtime.InteropServices.MarshalAsAttribute' attribute
-- 'Specified unmanaged type is only valid on fields.'

as a stab in the dark i managed to get this to compile
[return: MarshalAs(UnmanagedType.LPArray, SizeConst = 255)]
public static extern Byte[] DiskSaveFooter(string missionname,
string qlffilename, string id);

but the following line of implementation (pretty basic)
DiskSaveFooter("mis1", "", "000:000");
gave the following error:
Cannot marshal 'return value': Invalid managed/unmanaged type combination.

Soooooo Stuck.
I cant believe something so simple can be so hard!
Shaun

"G Himangi" wrote:

> You can try applying a MArshalAs(ByValArray, SIzeConst=260) to the return
> type of your method signature and change the return type from char[] to
> byte[]
>
> Did that work?
>
> ---------
> - G Himangi, Sky Software http://www....
> Shell MegaPack : GUI Controls For Drop-In Windows Explorer like Shell
> Browsing Functionality For Your App (.Net & ActiveX Editions).
> EZNamespaceExtensions.Net : Develop namespace extensions rapidly in .Net
> EZShellExtensions.Net : Develop all shell extensions,explorer bars and BHOs
> rapidly in .Net
> ---------
>
>
>
> "ShaunO" <ShaunO@discussions.microsoft.com> wrote in message
> news:7C3D477B-9C16-4011-8373-E88C572F9E7D@microsoft.com...
> > Thanks for the suggestion.
> > It errors with
> > A call to PInvoke function 'DLLTest!DLLTest.Q::DiskSaveFooter' has
> > unbalanced the stack. This is likely because the managed PInvoke signature
> > does not match the unmanaged target signature. Check that the calling
> > convention and parameters of the PInvoke signature match the target
> > unmanaged
> > signature.
> >
> > I get this error message on the
> > IntPtr ptr = qn.DiskSaveFooter("mis1", "", "000:000"); line.
> >
> > I think that Delphi's native strings are single-byte strings, whereas
> > .NET's are UTF-16 which may be affecting things but i get the above error
> > message when i define the return type as anything other than char[]
> >
> > Does this help?
> >
> >
> >
> > "G Himangi" wrote:
> >
> >> It may work if you define the function as
> >>
> >> [DllImport("qn.dll",
> >> CharSet=CharSet.Ansi,CallingConvention=CallingConvention.StdCall)]
> >>
> >> public static extern IntPtr DiskSaveFooter(string missionname, string
> >> qlffilename, string id);
> >>
> >> and then.....
> >>
> >> IntPtr ptr = qn.DiskSaveFooter("mis1", "", "000:000");
> >> char* charArray = (char*)ptr;
> >>
> >> this requires unsafe code though.
> >>
> >> Or you can use Marshal.Copy to copy the contents of the ptr to a
> >> char/byte
> >> array.
> >>
> >> ---------
> >> - G Himangi, Sky Software http://www....
> >> Shell MegaPack : GUI Controls For Drop-In Windows Explorer like Shell
> >> Browsing Functionality For Your App (.Net & ActiveX Editions).
> >> EZNamespaceExtensions.Net : Develop namespace extensions rapidly in .Net
> >> EZShellExtensions.Net : Develop all shell extensions,explorer bars and
> >> BHOs
> >> rapidly in .Net
> >> ---------
> >>
> >>
> >>
> >> "ShaunO" <ShaunO@discussions.microsoft.com> wrote in message
> >> news:941ABD0B-C05C-4636-A2D9-8F247D252E54@microsoft.com...
> >> > Hi,
> >> > I am trying to call an old Delphi .dll
> >> >
> >> > // DELPHI definition (should return an array of 256 chars)
> >> > function DiskSaveFooter(missionname,qlffilename,id:pchar):TCharArray;
> >> > export;
> >> >
> >> > // My C# definition
> >> > [DllImport("qn.dll",
> >> > CharSet=CharSet.Ansi,CallingConvention=CallingConvention.StdCall)]
> >> >
> >> > public static extern char[] DiskSaveFooter(string missionname, string
> >> > qlffilename, string id);
> >> >
> >> > // My C# Implementation
> >> > char []b = new char[256];
> >> > b = qn.DiskSaveFooter("mis1", "", "000:000");
> >> >
> >> >
> >> > I get the ERROR: Cannot marshal 'return value': Invalid
> >> > managed/unmanaged
> >> > type combination.
> >> >
> >> > Any suggestions please?
> >>
> >>
> >>
>
>
>

microsoft.public.dotnet.framework.interop

Cannot marshal 'return value'

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G Himangi

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G Himangi

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