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<< Click to Display Table of Contents >> Drag e Drop do Explorer |
  
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<< Click to Display Table of Contents >> Drag e Drop do Explorer |
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Como fazer um drag and drop de arquivos do Explorer para dentro de um Windows Forms
Tela
DragDropManager.cs
using System;
using System.Diagnostics;
using System.Windows.Forms;
namespace MarketMp3
{
/// <summary>
/// Interface which should be implemented by parent form to open files dropped from Windows Explorer.
/// </summary>
public interface IDropFileTarget
{
void OpenFiles(System.Array a);
}
/// <summary>
/// DragDropManager class allows to open files dropped from Windows Explorer in Windows Form application.
///
/// Using:
/// 1) Derive parent form from IDropFileTarget interface:
///
/// public class Form1 : System.Windows.Forms.Form, IDropFileTarget
///
/// 2) Implement IDropFileTarget interface in parent form:
///
/// public void OpenFiles(Array a)
/// {
/// // open files from array here
/// }
///
/// 3) Add member of this class to parent form:
///
/// private DragDropManager m_DragDropManager;
///
/// 4) Initialize class instance in parent form Load event:
///
/// private void Form1_Load(object sender, System.EventArgs e)
/// {
/// m_DragDropManager = new DragDropManager();
/// m_DragDropManager.Parent = this;
/// }
///
/// </summary>
public class DragDropManager
{
private Form m_parent; // reference to owner form
// delegate used in asynchronous call to parent form:
private delegate void DelegateOpenFiles(Array a); // type
private DelegateOpenFiles m_DelegateOpenFiles; // instance
public DragDropManager()
{
}
/// <summary>
/// Set reference to parent form and make initialization.
/// </summary>
public Form Parent
{
set
{
m_parent = value; // keep reference to parent form
// Check if parent form implements IDropFileTarget interface
if (!(m_parent is IDropFileTarget))
{
throw new Exception("DragDropManager: Parent form doesn't implement IDropFileTarget interface");
}
// create delegate used for asynchronous call
m_DelegateOpenFiles = new DelegateOpenFiles(((IDropFileTarget)m_parent).OpenFiles);
// ensure that parent form allows dropping
m_parent.AllowDrop = true;
// subscribe to parent form's drag-drop events
m_parent.DragEnter += new System.Windows.Forms.DragEventHandler(this.OnDragEnter);
m_parent.DragDrop += new System.Windows.Forms.DragEventHandler(this.OnDragDrop);
}
}
/// <summary>
/// Handle parent form DragEnter event
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void OnDragEnter(object sender, System.Windows.Forms.DragEventArgs e)
{
// If file is dragged, show cursor "Drop allowed"
if (e.Data.GetDataPresent(DataFormats.FileDrop))
e.Effect = DragDropEffects.Copy;
else
e.Effect = DragDropEffects.None;
}
/// <summary>
/// Handle parent form DragDrop event
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void OnDragDrop(object sender, System.Windows.Forms.DragEventArgs e)
{
try
{
// When file(s) are dragged from Explorer to the form, IDataObject
// contains array of file names. If one file is dragged,
// array contains one element.
Array a = (Array)e.Data.GetData(DataFormats.FileDrop);
if (a != null)
{
// Call parent's OpenFiles asynchronously.
// Explorer instance from which file is dropped is not responding
// all the time when DragDrop handler is active, so we need to return
// immidiately (especially if OpenFiles shows MessageBox).
m_parent.BeginInvoke(m_DelegateOpenFiles, new Object[] { a });
m_parent.Activate(); // in the case Explorer overlaps parent form
}
}
catch (Exception ex)
{
Trace.WriteLine("Error in DragDropManager.OnDragDrop function: " + ex.Message);
// don't show MessageBox here - Explorer is waiting !
}
}
}
}
Principal.cs
using System;
using System.IO;
using System.Windows.Forms;
namespace MarketMp3
{
public partial class Principal : Form, IDropFileTarget
{
private DragDropManager m_DragDropManager;
public Principal()
{
InitializeComponent();
}
private void Principal_Load(object sender, EventArgs e)
{
m_DragDropManager = new DragDropManager();
m_DragDropManager.Parent = this;
}
// este método é executado quando o usuário DROP arquivos aqui
public void OpenFiles(Array a)
{
string sError = "";
string sFile;
lstFiles.Items.Clear();
// process all files in array
for (int i = 0; i < a.Length; i++)
{
sFile = a.GetValue(i).ToString(); // file name
// Check file name
// (Let's say we don't accept non-existing files or directories)
FileInfo info = new FileInfo(sFile);
if (!info.Exists)
{
sError += "\nIncorrect file name: " + sFile;
}
else
{
lstFiles.Items.Add(sFile);
}
}
if (sError.Length > 0)
MessageBox.Show(this, sError, "Open File Error");
}
}
}