Question

咨询关于vb调用含有结构体dll（vc++开发，带有多输出函数值）问题

大家好！
看了很多本论坛上的帖子，很受启发，但是关于vb调用含有多输出函数值vc dll的问题很少涉及，我在编程过程中遇到了该方面问题，解决不了，希望得到大家指点，谢谢！

vc中cpp文件为：
struct res
{
double r;
double Wc;
double Wr;
};

struct res lo(double uo,double dw,double dm)
{
struct res result;
double r,Wc,Wr;

result.r =uo;
result.Wc=dw;
result.Wr=dm;
return result;

}

vb中代码：
Private Type js

x As Double

y As Double

z As Double

End Type

Private Declare Function lo Lib "sample1.dll" (ByVal uo As Double, ByVal dw As Double, ByVal dm As Double) As Double

Private Sub Command1_Click()

Dim n(3) As Double

n(3) = lo(CDbl(Text1.Text), CDbl(Text2.Text), CDbl(Text3.Text))
Text5.Text = n(0)
Text6.Text = n(1)
Text7.Text = n(2)
End Sub

其中函数为三输入三输出形式的，想实现的是将vb中三个TextBox 控件中输入的值传给vc开发的dll，通过调用lo函数返回三个结果值，谢谢！

Answer 1

这个吗，很简单的，用数组解决就可以：
vc的sample.cpp
int __stdcall fun(double a, double b, double * res)
{
res[0] = a + b;
res[1] = a - b;
res[2] = a * b;
res[3] = a / b;
return 0;
}
vc的sample.def
EXPORTS
fun

vb:
declare sub fun lib "sample.dll" (byval a as double, byval b as double, byref x as double)

private sub command1_click()
dim x(4) as double
fun 1,2,x(0)
text1.text = x(0)
text2.text = x(1)
text3.text = x(2)
text4.text = x(3)
end sub

在上面的例子里，把数组第一个元素传递给dll就可以作为返回值把东西带回来了