从Outlook拖拽附件到WinForm

当从OutLook中拖拽附件时，其拖拽的源共有四种DataFormat,其中FileGroupDescriptor 包含拖拽的文件名，FileContents中是文件内容。
当然Copy附件也是一样。

如下代码演示了一个简单的拖拽，并将拖拽的附件保存到了系统临时目录下。

//
// Program created by Thomas (Tom) F. Gueth, Binary Star Technology, Inc
//
// You are welcome to use this sample code in any manner you wish, commercial or otherwise.
//
// No warranty of any kind is made about this code.  It worked for me and I hope it works for you
//   and expands your knowledge of drag and drop technology.
//

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.IO;
using System.Text;
using System.Windows.Forms;

namespace TestEmailDragDrop
{
    /// <summary>
    /// Summary description for Form1.
    /// </summary>
    public class Form1 : System.Windows.Forms.Form
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.Container components = null;

        public Form1()
        {
            //
            // Required for Windows Form Designer support
            //
            InitializeComponent();

            //
            // TODO: Add any constructor code after InitializeComponent call
            //
        }

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        protected override void Dispose( bool disposing )
        {
            if( disposing )
            {
                if (components != null) 
                {
                    components.Dispose();
                }
            }
            base.Dispose( disposing );
        }

        #region Windows Form Designer generated code
        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            // 
            // Form1
            // 
            this.AllowDrop = true;
            this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
            this.ClientSize = new System.Drawing.Size(456, 341);
            this.Name = "Form1";
            this.Text = "Drag-and-Drop Email Attachment";
            this.DragDrop += new System.Windows.Forms.DragEventHandler(this.Form1_DragDrop);
            this.DragEnter += new System.Windows.Forms.DragEventHandler(this.Form1_DragEnter);

        }
        #endregion

        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main() 
        {
            Application.Run(new Form1());
        }

        private void Form1_DragEnter(object sender, System.Windows.Forms.DragEventArgs e)
        {
            // for this program, we allow a file to be dropped from Explorer
            if (e.Data.GetDataPresent(DataFormats.FileDrop)) 
            {    e.Effect = DragDropEffects.Copy;}
            //    or this tells us if it is an Outlook attachment drop
            else if (e.Data.GetDataPresent("FileGroupDescriptor"))
            {    e.Effect = DragDropEffects.Copy;}
            //    or none of the above
            else
            {    e.Effect = DragDropEffects.None;}
        }

        private void Form1_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
        {
            string [] fileNames = null;

            try
            {
                if ( e.Data.GetDataPresent(DataFormats.FileDrop,false) == true)
                {                    
                    fileNames = (string []) e.Data.GetData(DataFormats.FileDrop);
                    // handle each file passed as needed
                    foreach( string fileName in fileNames)
                    {
                        // do what you are going to do with each filename
                    }
                }
                else if (e.Data.GetDataPresent("FileGroupDescriptor"))
                {
                    //
                    // the first step here is to get the filename of the attachment and
                    //   build a full-path name so we can store it in the temporary folder
                    //

                    // set up to obtain the FileGroupDescriptor and extract the file name
                    Stream theStream = (Stream) e.Data.GetData("FileGroupDescriptor");
                    byte [] fileGroupDescriptor = new byte[512];
                    theStream.Read(fileGroupDescriptor,0,512);
                    // used to build the filename from the FileGroupDescriptor block
                    StringBuilder fileName = new StringBuilder("");
                    // this trick gets the filename of the passed attached file
                    for(int i=76; fileGroupDescriptor[i]!=0; i++)
                    {    fileName.Append(Convert.ToChar(fileGroupDescriptor[i]));}
                    theStream.Close();
                    string path = Path.GetTempPath();  // put the zip file into the temp directory
                    string theFile = path+fileName.ToString();  // create the full-path name

                    //
                    // Second step:  we have the file name.  Now we need to get the actual raw
                    //    data for the attached file and copy it to disk so we work on it.
                    //

                    // get the actual raw file into memory
                    MemoryStream ms = (MemoryStream) e.Data.GetData("FileContents",true);
                    // allocate enough bytes to hold the raw data
                    byte [] fileBytes = new byte[ms.Length];
                    // set starting position at first byte and read in the raw data
                    ms.Position = 0;
                    ms.Read(fileBytes,0,(int)ms.Length);
                    // create a file and save the raw zip file to it
                    FileStream fs = new FileStream(theFile,FileMode.Create);
                    fs.Write(fileBytes,0,(int)fileBytes.Length);

                    fs.Close();    // close the file

                    FileInfo tempFile = new FileInfo(theFile);

                    // always good to make sure we actually created the file
                    if ( tempFile.Exists == true)
                    {    
                        // for now, just delete what we created
                        tempFile.Delete();
                    }
                    else
                    {    Trace.WriteLine("File was not created!");}
                }

            }
            catch (Exception ex)
            {
                Trace.WriteLine("Error in DragDrop function: " + ex.Message);

                // don't use MessageBox here - Outlook or Explorer is waiting !
            }
        
        }
    }
}

代码源于：http://www.codeproject.com/KB/cs/testemaildragdrop.aspx