从 System.Runtime.InteropServices.Marshal C# 中找不到 GetActiveObject 的定义

Question

我正在尝试连接到正在运行的 Excel 实例，但是当我尝试使用以下代码片段时：

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

public Application StartExcel()
{
    Application instance = null;
    try
    {
        instance = (Application)Marshal.GetActiveObject("Excel.Application");
    }
    catch (COMException ex)
    {
        instance = new ApplicationClass();
    }

    return instance;
}

我在互联网上找到了类似的片段，但是当我编译此代码时，出现以下错误：

错误 CS0117：“Marshal”不包含“GetActiveObject”的定义。

我不知道为什么，因为我有以下 NuGet 包： - Microsoft.Office.Interop.Excel - System.Runtime.InteropServices

Answer 1

我们需要从源代码GitHub.Microsoft 中拉取 GetActiveObject(String ProgID) 函数

创建自己的类，例如 - Marshal2

并像以前一样使用

Marshal2.GetActiveObject(progID);

源代码

public static class Marshal2
{
    internal const String OLEAUT32 = "oleaut32.dll";
    internal const String OLE32 = "ole32.dll";

    [System.Security.SecurityCritical]  // auto-generated_required
    public static Object GetActiveObject(String progID)
    {
        Object obj = null;
        Guid clsid;

        // Call CLSIDFromProgIDEx first then fall back on CLSIDFromProgID if
        // CLSIDFromProgIDEx doesn't exist.
        try
        {
            CLSIDFromProgIDEx(progID, out clsid);
        }
        //            catch
        catch (Exception)
        {
            CLSIDFromProgID(progID, out clsid);
        }

        GetActiveObject(ref clsid, IntPtr.Zero, out obj);
        return obj;
    }

    //[DllImport(Microsoft.Win32.Win32Native.OLE32, PreserveSig = false)]
    [DllImport(OLE32, PreserveSig = false)]
    [ResourceExposure(ResourceScope.None)]
    [SuppressUnmanagedCodeSecurity]
    [System.Security.SecurityCritical]  // auto-generated
    private static extern void CLSIDFromProgIDEx([MarshalAs(UnmanagedType.LPWStr)] String progId, out Guid clsid);

    //[DllImport(Microsoft.Win32.Win32Native.OLE32, PreserveSig = false)]
    [DllImport(OLE32, PreserveSig = false)]
    [ResourceExposure(ResourceScope.None)]
    [SuppressUnmanagedCodeSecurity]
    [System.Security.SecurityCritical]  // auto-generated
    private static extern void CLSIDFromProgID([MarshalAs(UnmanagedType.LPWStr)] String progId, out Guid clsid);

    //[DllImport(Microsoft.Win32.Win32Native.OLEAUT32, PreserveSig = false)]
    [DllImport(OLEAUT32, PreserveSig = false)]
    [ResourceExposure(ResourceScope.None)]
    [SuppressUnmanagedCodeSecurity]
    [System.Security.SecurityCritical]  // auto-generated
    private static extern void GetActiveObject(ref Guid rclsid, IntPtr reserved, [MarshalAs(UnmanagedType.Interface)] out Object ppunk);

}

Answer 2

这仅适用于 .Net Framework，不适用于 .Net Core。请检查 .Net 项目类型。

https://learn.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.marshal.getactiveobject?view=netframework-4.8&viewFallbackFrom=netcore-2.2