Data retrieving from table

PoweRoy

i am trying to get some data out of records from a database
database is 3.6 and driver is 3.7
programmed this code in visual C# .net

what i accieved:
-connecting/disc to database
-open/close company
-listing of tables
-open/close tables
-listing of fields of a table

I am trying to get the data out of a record with GetFieldData()
htable and record are both handle's (int)
what i tried:

this one works partially, j is the size of the field and i retrieve that, only the var in the field i dont receive

//dll loader
[DllImport("cfront.dll", CallingConvention = CallingConvention.Cdecl)] 
		 private static extern int DBL_GetFieldData(string dst, int dstsize, int hTable, int record, int fieldnr);

//the parser
case "lr" : //list records
	int record = DBL_AllocRec(htable);
	DBL_InitRec(htable, record);
	string s = "temp string";
			
	if (DBL_FindRec(htable, record ,"-") )
	{
		int j = DBL_GetFieldData(s,100,htable, record,1);
		Console.WriteLine(Convert.ToString(j) + s);
		Console.WriteLine("findrec succes");

	}
	else result.Add("No records found"); 
	DBL_FreeRec(record);
	break;

also used

//the dll loading
[DllImport("cfront.dll", CallingConvention = CallingConvention.Cdecl)] 
		 private static extern int DBL_GetFieldData(char[]dst, int dstsize, int hTable, int record, int fieldnr);

//the parser
case "lr" : //list records
	int record = DBL_AllocRec(htable);
	DBL_InitRec(htable, record);
	char[] s = new char[100];
	
		
	if (DBL_FindRec(htable, record ,"-") )
	{
		int j = DBL_GetFieldData(s,100,htable, record,1);
		Console.WriteLine(Convert.ToString(j));

		string temp = "";
		for (int k = 0 ; k < 100 ; k++) 
		{
			temp = temp + s[k];
		}
		Console.WriteLine(temp);
		Console.WriteLine("findrec succes");
	}
	else result.Add("No records found"); 
	DBL_FreeRec(record);
	break;

also tried with both the examples to use the 1 param as a ref (ref string dst )

is i use the function DBL_GetFieldData(int hTable, int record, int fieldnr);
i get a NullReferenceException
with
DBL_GetFieldData(int hTable, int record, int fieldnr); i tried to receive a object cause in VB u receive a variant. no succes

Could anyone look at the code an give me a sollution for this prob that's bothering for couple of days :P

PoweRoy

*bump*

Noone knows a sollution?

meanwhile i tried to start another project and try to connect with odbc only the .open isnt working :P suspect the connection string, but whats the valid one for navision?..

PoweRoy

cause the first param is a void* i thought using a IntPtr could be helpfull but still i dont get any data:

[DllImport("cfront.dll", CallingConvention = CallingConvention.Cdecl)] 
         private static extern int DBL_GetFieldData( IntPtr dst, int dstsize, int hTable, int record, int fieldnr);

case "lr" : //list records
                    int record = DBL_AllocRec(htable);
                    //DBL_InitRec(htable, record); not needed only for changing and inserting a record
                    IntPtr s = new IntPtr();
                            
                    if (DBL_FindRec(htable, record ,"-") )
                    {
                        
                        int j = DBL_GetFieldData(s,100,htable, record,1);
                        Console.WriteLine(Convert.ToString(j)+Marshal.PtrToStringAnsi(s));

                        Console.WriteLine("findrec gelukt");
                    }; 
                    break;

but it gives a "An unhandled exception of type 'System.NullReferenceException' occurred in csharptest.exe

Additional information: Object reference not set to an instance of an object" error

are there any other solutions?

PoweRoy

due the conversion probs i found a program that convert a .h file to c# code. The program is called Pinvoke Wizard made by Paul Yao, but the problem is that it cant convert the typedefs

is there another way to make the .h file usefull in c#?