vb调用vc写的dll的几种方式总结.txt

VB调用VC写的dll的几种方式总结(有VB和VC的示例代码）

第一种类型：数值传递：
注意：在VB中，默认变量传递方式为ByRef为地址，而传递值就是用ByVal，还要注意在C++中，
	int类型的变量是32位的，在VB中要用long型变量来配合。
C++：
extern "C" _declspec(dllexport) int __stdcall TestCalc(int source)
{
	//AFX_MANAGE_STATE(AfxGetStaticModuleState());
	return(++source);
}

.def文件
EXPORTS TestCalc

VB声明：
Private Declare Function TestCalc Lib "Dll.dll" (ByVal Source As Long) As Long
调用：
Dim Tint As Long
Tint = TestCalc(45)
MsgBox Tint, vbExclamation




第二种类型：传递字符串，主要用于字符串返回或者处理。
C++：
extern "C" _declspec(dllexport) int __stdcall MidStr(CHAR * src,CHAR * dest)
{
	//AFX_MANAGE_STATE(AfxGetStaticModuleState());
	strcpy(dest,src+1);
	return 0;
}

.def文件
EXPORTS MidStr

VB中声明：
Private Declare Function MidStr Lib "Dll.dll" (ByVal src As String, ByVal dest As String) As Long

调用：
Dim i As Long, s As String * 255
tempstr = "Hello!World"
i = MidStr(tempstr, s)  或者 i = MidStr("Hello!World", s)
MsgBox s, vbExclamation





第三种类型：传递数组和变量指针，主要用于从dll中读出大量数据
C++：
extern "C" _declspec(dllexport) int __stdcall TestByte(BYTE *p,int *length)
{
	//AFX_MANAGE_STATE(AfxGetStaticModuleState());
	*p=45;
	*(p+1)=46;
	*length=2;
	return 0;
}

.def文件
EXPORTS TestByte

Private Declare Function TestByte Lib "Dll.dll" (ByRef src As Any, ByRef length As Long) As Long
VB调用：
Dim a(0 To 10) As Byte
Dim i As Integer, length As Long
i = TestByte(a(0), length)
MsgBox a(0) & " " & a(1) & vbCrLf & length, vbExclamation