C# wrapper error code 6202

[luuuu]

I am writing a wrapper in C# to read TDM files.

OpenEx works fine.

        [DllImport(lib, CharSet = CharSet.Auto)]
        static extern int DDC_OpenFileEx(
            [MarshalAs(UnmanagedType.LPStr)]
                            string filePath,
            [MarshalAs(UnmanagedType.LPStr)]
			   string fileType,
                            int read_only,
                            ref long file);

 but

        [DllImport(lib, CharSet = CharSet.Auto)]
static extern int DDC_GetFileStringPropertyLength(long file, 
[MarshalAs(UnmanagedType.LPStr)]                     
 string property, 
ref int length);
      int len = 0;
            errCode = ReadTDM.DDC_GetFileStringPropertyLength(fileh, "name", ref len);// fileh is passed form OpenEx fun
            System.Console.WriteLine("length {0}", len);
            System.Console.WriteLine("Error Code {0}", errCode); 

 gives me an error  An invalid argument was passed to the library. I had tried ref uint length , didn't help.
 

[AndreasK]

We looked at the source code for DDC_GetFileStringPropertyLength and the only things that would cause it to

return DDC_InvalidArgument (-6202) is:

• if the property name char* input parameter (2nd parameter) is NULL or empty string
• if the length unsigned int* output parameter is NULL.

I'm not familiar enough with C# to tell whether there are any problems in the declarations of the DLL functions

or in how they are being called but maybe that helps you to solve the issue.

[luuuu]

Thx for the reply.

I found out that I have two headers files nilibddc_m.h and nilibddc.h

in first one DDCFileHandle is a long type in the second on is a structure 

typedef struct _DDCFile				DDCFile;
typedef struct _DDCChannelGroup		        DDCChannelGroup;
typedef struct _DDCChannel			DDCChannel;

typedef DDCFile*				DDCFileHandle;
typedef DDCChannelGroup*			DDCChannelGroupHandle;
typedef DDCChannel*				DDCChannelHandle;

 but according to your post it should not be the cause of this error, should be?

[luuuu]

some additional info:

Windows 7 32bit and lib form the 32-bit subfoler

example SinData.tdm form http://digital.ni.com/public.nsf/allkb/A3663DE39D6A2C5A86257204005C11CA?OpenDocument

and the String is not the problem

        /// <summary>
        /// GetNumChannelGroups
        /// </summary>
        [DllImport(lib)]
        static extern int DDC_GetNumChannelGroups(long file,
                                       ref uint numChannelGroups);

 

                uint numGru = 0;
                errCode = ReadTDM.DDC_GetNumChannelGroups(fileh, ref numGru);
                System.Console.WriteLine("Error Code {0}  GetNumChannelGroups", errCode);

 also returs the -6202 code, hence is numGru.

[luuuu]

Solved 🙂

file must be int not long

http://digital.ni.com/public.nsf/allkb/A3663DE39D6A2C5A86257204005C11CA?OpenDocument 

 nilibddc.h says

 typedef long            DDCFileHandle;
typedef long            DDCChannelGroupHandle;
typedef long            DDCChannelHandle;