.net - 将C++ POS控件与.NET POS SDK接口(interface)时出现问题

我们正在尝试实现一个支持COM接口(interface)的.NET服务对象，以模拟POSPrinter，但仍与较早的技术兼容。

在下面的类中，我们有接口(interface)和类对象。

using [...]

namespace yRPOSPrinterDotNet
{
    [Guid("2D570F11-4BD8-40e7-BF14-38772063AAF0")]
    [InterfaceType(ComInterfaceType.InterfaceIsDual)]
    public interface yRPosPrinterCOM
    {

        long Open(String DeviceName);
        long PrintNormal(long Station, String Data);

    }

    [Guid("478176F4-5105-435c-8EBC-D4CB90B7B1C7")]
    [ClassInterface(ClassInterfaceType.None)]
    //[ProgId("yRPOSPrinterDotNet.POSPrinter")] //will be set automatically as the progid <namespace><clsid>
    public class POSPrinter : yRPosPrinterCOM
    {

        #region yRPosPrinterCOM Members
        public long Open()
        {
            return 0;
        }

        public long Open(String DeviceName)
        {
            Trace.Listeners.Add(new TextWriterTraceListener(Console.Out));
            FileStream objStream = new FileStream("C:\\yRPOSLog.txt", FileMode.OpenOrCreate);
            TextWriterTraceListener objTraceListener = new TextWriterTraceListener(objStream);
            Trace.Listeners.Add(objTraceListener);
            Trace.AutoFlush = true;
            Trace.Indent();
            Trace.WriteLine("Entering Main");
            Debug.WriteLine("How does this one do??");
            Console.WriteLine("Hello World.");
            Trace.WriteLine("Exiting Main");
            Trace.Unindent();
            return 0;
        }


        public long PrintNormal(long Station, string Data)
        {
            throw new NotImplementedException();
        }

        #endregion
    }

}

并在HKEY_LOCAL_MACHINE\SOFTWARE\OLEforRetail\ServiceOPOS\POSPrinter\yReceipts中放入我们的yRPosPrinterDotNet.POSPrinter的ProgID
HKEY_CLASSES_ROOT\CLSID\{478176F4-5105-435C-8EBC-D4CB90B7B1C7}构建后正确拥有我们的ProgID(yRPosPrinterDotNet.POSPrinter)

我们可以使用此类通过以下测试类调用DLL(查找ProgID):

using [...]

namespace TestYRPosPrinterDotNet
{
    /// <summary>
    /// Summary description for UnitTest1
    /// </summary>
    [TestClass]
    public class UnitTest1
    {
        public UnitTest1()
        {

        }

        private TestContext testContextInstance;

        /// <summary>
        ///Gets or sets the test context which provides
        ///information about and functionality for the current test run.
        ///</summary>
        public TestContext TestContext
        {
            get
            {
                return testContextInstance;
            }
            set
            {
                testContextInstance = value;
            }
        }

        [TestMethod]
        public void TestMethod1()
        {
            String sProgID = "yRPosPrinterDotNet.POSPrinter";
            // We get the type using just the ProgID
            Type oType = Type.GetTypeFromProgID(sProgID);
            if (oType != null)
            {
               POSPrinter pp = (POSPrinter)Activator.CreateInstance(oType);
               long retVal = pp.Open("Nothing");
            }

        }
    }
}

但是，当我们尝试通过示例TestApp调用时(它确实显示为serviceObject)

{"Method Open threw an exception.  The service object does not support one or more of the methods required by its release."} System.Exception {Microsoft.PointOfService.PosControlException}

通过示例C++控件对象，我们在opos.h中收到定义为104的(const LONG OPOS_E_NOSERVICE = 4 + OPOSERR;)，并带有以下堆栈跟踪

----------------------------------- Doesn't work --------------------------------------------------------

 POSPrinterExample.exe!COleDispatchDriver::InvokeHelperV(long dwDispID=37, unsigned short wFlags=1, unsigned short vtRet=3, void * pvRet=0x0012f1e0, const unsigned char * pbParamInfo=0x00702014, char * argList=0x0012f110)  Line

397 C++
 POSPrinterExample.exe!COleControlSite::InvokeHelperV(long dwDispID=37, unsigned short wFlags=1, unsigned short vtRet=3, void * pvRet=0x0012f1e0, const unsigned char * pbParamInfo=0x00702014, char * argList=0x0012f10c)  Line 1093

C++
  POSPrinterExample.exe!CWnd::InvokeHelper(long dwDispID=37, unsigned short wFlags=1, unsigned short vtRet=3, void * pvRet=0x0012f1e0, const unsigned char * pbParamInfo=0x00702014, ...)  Line 382 C++
  POSPrinterExample.exe!COPOSPOSPrinter::Open(const char * DeviceName=0x00271f00)  Line 192 + 0x1c bytes C++

最佳答案

这似乎是DispInterface。这是支持Visual Basic的可怕COM技巧。基本上，所有功能都已编号。在第一次调用时，将查找并缓存所有功能编号。例如，您似乎缺少了Close()函数。这将导致它以您看到的方式失败查找。

引自“OLE for Retail POS Control Guide-Rel。1.1”: