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copied!<p><strong>Getting the filenames</strong></p> <p>Getting the filenames is easy. Just call:</p> <pre><code>dragEventArgs.Data.GetData("FileGroupDescriptorW") </code></pre> <p>this will return a <code>MemoryStream</code> that contains a <code>FILEGROUPDESCRIPTORA</code> structure. This can be parsed to get the filenames. <a href="http://www.codeproject.com/KB/office/outlook_drag_drop_in_cs.aspx" rel="noreferrer">Here</a> and <a href="http://www.codeproject.com/KB/cs/testemaildragdrop.aspx?df=100&forumid=51309&exp=0&select=1553102" rel="noreferrer">here</a> are links to projects on CodeProject that show you two different ways to parse <code>FILEGROUPDESCRIPTORA</code> in C#, so I won't go into detail here. I would probably use the technique described in the first project.</p> <p><strong>Getting the actual data</strong></p> <p>To get the actual data, you use the <code>FileContents</code> format. Unfortunately you either have to use reflection to access private methods, or write some COM interop yourself. The problem is that to get the data you must call the <code>System.Runtime.InteropServices.ComTypes.IDataObject</code> interface with a FORMATETC structure that has lindex set to the item index. Unfortunately System.Windows.DataObject's implementation always calls it with lindex=-1.</p> <p>The easiest solution is probably to use reflection to call private members of WPF's <code>DataObject</code>. Be forewarned, however, that this may break your code in future NET Framework versions. If that is completely unacceptable, your other option is to call the <code>RegisterDragDrop</code> function in <code>ole32.dll</code> to register a custom <code>IOleDropTarget</code>, then talk directly to the COM <code>IDataObject</code> that is passed in. This is not terribly difficult, but the reflection solution is much easier and will probably work for many versions of NET Framework, so that is what I will focus on.</p> <p>Here is what to do to retrieve a FileContent for a particular index:</p> <ol> <li>Reflect on the actual class of the data object to find a method called "GetData" that takes four arguments</li> <li>If the method was not found, reflect again to find a field of type <code>System.Windows.IDataObject</code>, get its value, and go back to step 1 (recursion is safe here)</li> <li>Use <code>MethodInfo.Invoke</code> to call the "GetData" you found with arguments: "FileContents", false, ComTypes.DVASPECT, lindex</li> <li>Read the file data from the returned <code>MemoryStream</code></li> </ol> <p>Here is the gist of the code to retrieve the file contents for a given index:</p> <pre><code>public MemoryStream GetFileContents(IDataObject dataObject, int index) { MethodInfo getData = ( from method in dataObject.GetType().GetMethods(BindingFlags.NonPublic | BindingFlags.Instance) where method.Name=="GetData" && method.GetParameters().Length==4 select method ).FirstOrDefault(); if(getData==null) { FieldInfo innerField = ( from field in dataObject.GetType().GetFields() where field.FieldType == typeof(IDataObject) select field ).FirstOrDefault(); if(innerField==null) throw new Exception("Cannot get FileContents from DataObject of type" + dataObject.GetType()); return GetFileContents((IDataObject)innerField.GetValue(dataObject), index); } return (MemoryStream)getData.Invoke(dataObject, new object[] { "FileContents", false, System.Runtime.InteropServices.ComTypes.DVASPECT.DVASPECT_CONTENT, index }); } </code></pre>

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