如何使用Marshal.QueryInterface？

问题描述

我想在Word文档中某些嵌入对象的工作。较早的海报告诉我，这是不是直线前进。这里是链接答案的摘录：

So I am interested in exposing which interface the object is implementing. The closest I could find is here. The code so far is below and any help with the Marshal.QueryInterface is greatly appreciated.

// Opening the word document
object missing = Type.Missing;
this.document = wordApp.Documents.Open(
                ref fn, ref confirmConversions, ref readOnly, ref missing, ref missing, ref missing,
                ref missing, ref missing, ref missing, ref missing, ref missing,
                ref missing, ref missing, ref missing, ref missing, ref missing);

foreach (Microsoft.Office.Interop.Word.InlineShape inlineShape in this.document.InlineShapes)
            {
                if (inlineShape.OLEFormat.ProgID != null)
                {
                    switch (inlineShape.OLEFormat.ProgID)
                    {
                        // This is a pdf file
                        case "AcroExch.Document.7":
                            //Marshal.QueryInterface(IntPtr pUnk, ref Guid iid, out IntPtr ppv);
                            break;
                        default:
                            break;
                    }
                }
            }

解决方案

Marshal.QueryInterface shouldn't be necessary - if you take a COM object and cast it to a COM interface type, .NET does the QueryInterface call for you. That is, you can write: IPersistStorage persist = (IPersistStorage) obj;

However it's not clear to me which object in the code implements IPersistStorage, IPersistStreamInit etc.

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