使用C#编写的COM加载项与自动加载项的可选参数

我正在开发一个COM加载项和Excel自动化加载项库,其核心代码是用C#编写的.我想为函数设置一个可选参数,我知道这对于C#和VBA,甚至Excel WorksheetFunction都是合法的.但我发现最终可选参数专门用于COM和Automation加载项,这意味着如果首先运行一个加载项,那么效果很好但另一个加载项的可选参数将不起作用.

下面请看示例:

在VS 2013解决方案中,我有两个项目:一个被调用TestVBA,另一个被调用TestExcel.

TestVBA用于COM加载项并通过"Excel 2013加载项"构建,有两个.cs文件:

ThisAddIn.cs

此文件自动生成并稍作修改.代码是

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Linq;
using Excel = Microsoft.Office.Interop.Excel;
using Office = Microsoft.Office.Core;
using Microsoft.Office.Tools.Excel;

namespace TestVBA
{
    public partial class ThisAddIn
    {
        private void ThisAddIn_Startup(object sender, System.EventArgs e)
        {
        }

        private void ThisAddIn_Shutdown(object sender, System.EventArgs e)
        {
        }

        private ExcelVBA oExcelVBA;

        protected override object RequestComAddInAutomationService()
        {
            if (oExcelVBA == null)
            {
                oExcelVBA = new ExcelVBA();
            }
            return oExcelVBA;
        }
        #region VSTO generated code

        /// 

        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// 
        private void InternalStartup()
        {
            this.Startup += new System.EventHandler(ThisAddIn_Startup);
            this.Shutdown += new System.EventHandler(ThisAddIn_Shutdown);
        }

        #endregion
    }
}

TestVBA.cs

此文件是COM加载项的主要计算文件.代码是

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.Runtime.InteropServices;
using Excel = Microsoft.Office.Interop.Excel;

using System.Reflection;


namespace TestVBA
{
    [ComVisible(true)]
    [ClassInterface(ClassInterfaceType.AutoDual)]
    public class ExcelVBA
    {
        public int TestAddVBA(int a = 1, int b = 1)
        {
            return a + b;
        }
    }
}

另一个TestExcel是Excel Automation加载项,通过C#"类库"构建,有两个.cs文件:

BaseUDF.cs

此文件定义了两个属性的装饰.代码是

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.Runtime.InteropServices;
using Microsoft.Win32;

namespace BaseUDF
{
    [ClassInterface(ClassInterfaceType.AutoDual)]
    [ComVisible(true)]
    public abstract class BaseUDF
    {
        [ComRegisterFunctionAttribute]
        public static void RegisterFunction(Type type)
        {
            // Add the "Programmable" registry key under CLSID.
            Registry.ClassesRoot.CreateSubKey(
              GetSubKeyName(type, "Programmable"));
            // Register the full path to mscoree.dll which makes Excel happier.
            RegistryKey key = Registry.ClassesRoot.OpenSubKey(
              GetSubKeyName(type, "InprocServer32"), true);
            key.SetValue("",
              System.Environment.SystemDirectory + @"\mscoree.dll",
              RegistryValueKind.String);
        }

        [ComUnregisterFunctionAttribute]
        public static void UnregisterFunction(Type type)
        {
            // Remove the "Programmable" registry key under CLSID.
            Registry.ClassesRoot.DeleteSubKey(
              GetSubKeyName(type, "Programmable"), false);
        }

        private static string GetSubKeyName(Type type,
          string subKeyName)
        {
            System.Text.StringBuilder s =
              new System.Text.StringBuilder();
            s.Append(@"CLSID\{");
            s.Append(type.GUID.ToString().ToUpper());
            s.Append(@"}\");
            s.Append(subKeyName);
            return s.ToString();
        }

        // Hiding these methods from Excel.
        [ComVisible(false)]
        public override string ToString()
        {
            return base.ToString();
        }

        [ComVisible(false)]
        public override bool Equals(object obj)
        {
            return base.Equals(obj);
        }

        [ComVisible(false)]
        public override int GetHashCode()
        {
            return base.GetHashCode();
        }
    }
}

TestExcel.cs

此文件是Excel Automation加载项的主要计算文件.代码是

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Microsoft.Win32;
using System.Runtime.InteropServices;
using Excel = Microsoft.Office.Interop.Excel;
using Extensibility;

namespace TestExcel
{
    [Guid("7127696E-AB87-427a-BC85-AB3CBA301CF3")]
    [ClassInterface(ClassInterfaceType.AutoDual)]
    [ComVisible(true)]
    public class TestExcel : BaseUDF.BaseUDF
    {
        public int TestAddExcel(int a = 1, int b = 1)
        {
            return a + b;
        }
    }
}

构建之后,两个加载项已在系统中注册,在Excel中我们可以成功使用它们.

对于自动化加载,我们称他们在电子表格=TestAddExcel(2,3)和=TestAddExcel()他们都很好地工作,并给予正确的结果5和2.但是,当我尝试通过COM调用COM加载项时

Sub TestVBA_Click()

Dim addIn As COMAddIn
Dim TesthObj As Object

Set addIn = Application.COMAddIns("TestVBA")
Set TestObj = addIn.Object

Range("Output").Value2 = TestObj.TestAddVBA(2, 3)
Range("Output").Offset(1, 0).Value2 = TestObj.TestAddVBA()

End Sub

使用所有参数存在的第一个调用运行良好,但对于缺少参数的第二个调用显示错误Type mismatch.

有趣的是,当我关闭测试excel文件并再次打开它时,这次我首先测试COM加载项,仍然通过上面的VBA代码,两个调用都工作得很好.然后,当我测试过去运行良好的两个电子表格函数时,只有第一个是好的,第二个缺少参数的函数=TestAddExcel()失败了#VALUE!.

如果有人可以帮助解决这个奇怪的问题,那将是非常好的.