EnumerableViewOfDispatch.cs

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using System.Collections;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices.ComTypes;
 
namespace System.Runtime.InteropServices.CustomMarshalers;
 
internal sealed class EnumerableViewOfDispatch : ICustomAdapter, System.Collections.IEnumerable
{
    private const int DISPID_NEWENUM = -4;
 
    private const int LCID_DEFAULT = 1;
 
    private readonly object _dispatch;
 
    private IDispatch Dispatch => (IDispatch)_dispatch;
 
    public EnumerableViewOfDispatch(object dispatch)
    {
        _dispatch = dispatch;
    }
 
    public unsafe System.Collections.IEnumerator GetEnumerator()
    {
        System.Runtime.CompilerServices.Unsafe.SkipInit(out Variant variant);
        void* value = &variant;
        DISPPARAMS pDispParams = default(DISPPARAMS);
        Guid riid = Guid.Empty;
        Dispatch.Invoke(-4, ref riid, 1, InvokeFlags.DISPATCH_METHOD | InvokeFlags.DISPATCH_PROPERTYGET, ref pDispParams, new IntPtr(value), IntPtr.Zero, IntPtr.Zero);
        IntPtr intPtr = IntPtr.Zero;
        try
        {
            object obj = variant.ToObject();
            if (!(obj is IEnumVARIANT o))
            {
                throw new InvalidOperationException(SR.InvalidOp_InvalidNewEnumVariant);
            }
            intPtr = Marshal.GetIUnknownForObject(o);
            return (System.Collections.IEnumerator)EnumeratorToEnumVariantMarshaler.GetInstance(null).MarshalNativeToManaged(intPtr);
        }
        finally
        {
            variant.Clear();
            if (intPtr != IntPtr.Zero)
            {
                Marshal.Release(intPtr);
            }
        }
    }
 
    public object GetUnderlyingObject()
    {
        return _dispatch;
    }
}