How does the function of the dll written by vc pass the string to vb?

鱼松卷

vc writes dll, I can only write int type functions:

__stdcall int CALLBACK CalcSum(int a,int b);

You can declare in vb:
Private Declare Function MySum Lib "d:\MyDLL.dll" (ByVal S As Integer, ByVal D As Integer) As Integer


This can be used in vb, but now I want to write a function in dll that can return a string, and use the label control of vb to display the string returned by the function. How do I write it in dll? How do I declare it in vb? How does the label control call it? Please help!

zdl_22

__stdcall int CALLBACK CalcSum(int a,int b,char *c);

You can declare in vb:
Private Declare Function MySum Lib "d:\MyDLL.dll" (ByVal S As Integer, ByVal D As Integer, ByRef c as string) As Integer

72次灌水被抓

BSTR/VARANT

shaziahlx

Use BSTR

CString::AllocSysString
BSTR AllocSysString () const;
throw( CMemoryException );

Return Value

Points to the newly allocated string.


or
SysAllocString
BSTR SysAllocString(
  OLECHAR FAR* sz
);

霜之哀愁

__stdcall char * CALLBACK CalcSum(int a,int b);

The return value of the function defined in vb is just a string type or a character pointer. . .

waftwind

vc write dll, vb call, interesting.

lcdxhj

BSTR, RETVAL, ByRef

falconwbgjdl

Try:
Convert String in VB to BSTR in VC, just change the parameter type, but pay attention to using ByRef