VC2015编写的DLL给其他语言调用

(1)用C++builder6调用DLL
用VC2015创建包含MFC库的DLL,如果是给C++Builder6使用，步骤如下:
1、工程属性==》C++==》高级==》调用约定 选项为：__stdcall (/Gd)
2、VC++2015中的函数声明如下：
extern "C" __declspec(dllexport) VOID __stdcall CreateMeter(const char* szTypeName);
3.VC++2015的def文件,EXPORTS可以不用写，因为C++Builder6不用到这个.lib文件
不过,我发现要导出函数,需要在def字声明,否则在其他语言中找不到函数,提示错误.
4.在C++Builder6中,需要重新导出DLL的引导库.lib，方法如下：
implib my.lib my.dll
在BCB6工程中引入my.lib，同时添加函数声明，也就是VC2015DLL中的函数声明(与第2步相同)

(2)用Delphi7调用

unit ScaleWeight_dll;
interface
procedure  CreateMeter(xktype:PChar;
No:integer;
Comm:integer;
baud:integer;
parity:Char;
databit:integer;
stopbit:integer
);stdcall;external 'YuComm.dll';
//获取重量字符串
function  GetWeight( buff :pchar;index :integer = 1):PChar;stdcall;
external 'YuComm.dll';
//写串口
procedure WritePort( buff :array of byte;index :integer = 0);stdcall;
external 'YuComm.dll';
function ClosePort(index :integer=1):integer;stdcall;external 'YuComm.dll';
//name 'ClosePort1';

//辅助函数
//缓取缓冲区数据量
function GetBuffLength(index :integer =0):integer;stdcall;
external 'YuComm.dll';
//或取通信状态；true串口打开但通信中断，false通信正常
function GetStatus(index :integer =0):boolean;stdcall;external 'YuComm.dll';
//清除缓冲区数据
//procedure Clear(index :integer =0);stdcall;external 'YuComm.dll';
//获取原始数据
function  GetSourceData( buff :pbyte;index :integer = 0):integer;stdcall;
external 'YuComm.dll';

implementation

end.

将上面文件保存为扩展名为pas的文件,添加到delphi7工程中.
(3)在VB6中调用DLL

Private Declare Function CreateMeter Lib "YuComm"(ByVal name As String, _
ByVal No As Integer, _
ByVal port As Integer, _
ByVal baud As Integer, _
ByVal parity As Integer, _
ByVal databit As Integer, _
ByVal stopbit As Integer) As Boolean'需要添加一个返回值声明,即使不需要
Private Declare Function GetWeight Lib "YuComm"(ByVal buff As String,
Optional ByVal index As Integer = 1) As Long
Private Declare Function GetStatus Lib "YuComm"(Optional ByVal index As Integer = 1)
As Integer
Private Declare Function ClosePort Lib "YuComm"(Optional ByVal index As Integer = 1)
As Boolean

Private Sub Command1_Click()
Dim name As String
Dim port As Integer
Dim baud As Integer

name = Combo1.Text
port = CInt(Text1.Text)
baud = CInt(Text2.Text)
CreateMeter name, 1, port, baud, 110, 8, 1

End Sub

Private Sub Command2_Click()
ClosePort (1)
End Sub

Private Sub Command3_Click()

End Sub

Private Sub Timer1_Timer()
Dim re As Boolean

re = GetStatus(1)
If re = True Then
Label2.Caption = "串口打开成功"
Else
Label2.Caption = "串口打不成功"
End If

Dim buff1  As String
buff1 = Space(100)
Call GetWeight(buff1, 1)
Label1.Caption = buff1

End Sub

在XP平台下,用VB6调用,请用release方式编译,否则VB6会提示找不到相应的DLL文件,即所这个文件就在运行目录下
在VB中调用,声明函数时应加上返回值,即使DLL中这个函数没有返回值.返回值的类型可任意
(4)在C#中调用DLL

public partial class Form1 : Form
{
//========================================================================
//1、创建仪表，并打开仪
[DllImport("YuComm.dll")]
public static extern bool CreateMeter(string xktype,int no,int comm,
int baud,int parity,int databit,int stopbit);
//2、读取仪表重量，多台仪表时，参数为索引
[DllImport("YuComm.dll")]
public static extern string GetWeight(StringBuilder weight, int index = 1);
//写串口
[DllImport("YuComm.dll")]
public static extern void Write(ref byte buff,int index = 1);
//3、关闭串口
[DllImport("YuComm.dll")]
public static extern void ClosePort( int index=1);

//ScaleWeight辅助功能函数：获取缓冲区数据个数
[DllImport("YuComm.dll")]
public static extern int GetBuffLength(int index = 1);
//获取通信状态：false通信正常 ，true通信中断
[DllImport("YuComm.dll")]
public static extern bool GetStatus(int index=1);
//辅助功能函数：读取原始数据流
[DllImport("YuComm.dll")]
public static extern int GetSourceData(ref byte buff, int index = 1);
//辅助功能函数：清除缓冲区
//[DllImport("YuComm.dll")]
//public static extern void Clear(int index=1);
//===================================================================
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
xktype  = comboBox1.Text;
szComm    = textBox1.Text;
szBaud = textBox2.Text;

bool re = CreateMeter(xktype, 1, Convert.ToInt32(szComm),
Convert.ToInt32(szBaud), 'n', 8, 1);
if (re)
{
label1.Text = "串口状态：打开成功";
}
else
{
label1.Text = "串口状态：打开不成功";
}
}

private void button2_Click(object sender, EventArgs e)
{
ClosePort(1);
label1.Text = "串口状态：串口关闭";
}

private void timer1_Tick(object sender, EventArgs e)
{
StringBuilder buff = new StringBuilder(255);
GetWeight(buff,1);
label2.Text = buff.ToString();
buff = null;//释放

label5.Text = "缓冲区中数据量："+ GetBuffLength().ToString();

bool re = GetStatus();
if (re)
label4.Text = "通信状态：通信数据流正常";
else
label4.Text = "通信状态：通信数据流中断";

byte[] data = new byte[1024];
int c = GetSourceData(ref data[0],1);
richTextBox1.Clear();
for (int i = 0; i < c; i++)
{
richTextBox1.Text += data[i].ToString("X2") +" ";
}
data = null;

}

private void button3_Click(object sender, EventArgs e)
{
byte[] buff = new byte[1024];
string a = "hello";
BitConverter.ToString(buff);
Write(ref buff[0], 1);
buff = null;
}

private void button4_Click(object sender, EventArgs e)
{
timer1.Enabled = !timer1.Enabled;
if (timer1.Enabled)
button4.Text = "暂停";
else
button4.Text = "开始";
}

}

在XP上运行,请使用release方式编译发布,否则调用DLL中的函数时会报错!