有时候我们方便用户操作，总会把一下Copy/Paste 或者 input操作转换为Drag/Drop, WPF 跟之前WinForm 一样提供了一些实现方式方便开发人员进行开发。
要允许控件Drop操作，首先必须设置控件属性AllowDrop，这样控件才能产生DragOver/DragEnter/Drop等相关事件，从而开发人员可以做一些逻辑判断，设置DragEventArgs 的属性Effects 决定Drag的内容是否允许Drop. 下面是一个简单的例子：
创建两个ListBox, 一个里面有内容（名字为：EmployeeSource），另外一个（名字：SelectedEmployees）没有内容，允许用户从EmployeeSource 拖拽内容到SelectedEmployees。
1. 在Xaml中创建这两个ListBox, 并进行相关数据绑定
<ListBox x:Name="SelectedEmployees" HorizontalAlignment="Left" Height="100" Margin="35,30,0,0"
ItemsSource="{Binding SelectedEmployeeData}" DisplayMemberPath="Description"
VerticalAlignment="Top" Width="275" AllowDrop="True"
Drop="SelectedEmployees_Drop" DragOver="SelectedEmployees_DragOver" DragLeave="SelectedEmployees_DragLeave"
MouseMove="SelectedEmployees_MouseMove"/>
<ListBox x:Name="EmployeeSource" DataContext="{Binding Source={StaticResource EmployeeList}}"
SelectionMode="Single" HorizontalAlignment="Left" Height="100" Margin="35,255,0,0" VerticalAlignment="Top" Width="280"
ItemsSource="{Binding Employees}" DisplayMemberPath="Description" MouseMove="EmployeeSource_MouseMove"/> bool bMouseDown = true;
private void EmployeeSource_MouseMove(object sender, System.Windows.Input.MouseEventArgs e)
{
// TODO: Add event handler implementation here.
bMouseDown = e.LeftButton == MouseButtonState.Pressed;
if (EmployeeSource.SelectedItems.Count == 0 || !bMouseDown)
return;
ICollection<EmployeesItem> selected = new List<EmployeesItem>();
foreach(var item in EmployeeSource.SelectedItems)
{
var employee = item as EmployeesItem;
if (employee == null)
return;
selected.Add(employee);
}
DragDrop.DoDragDrop(EmployeeSource, selected, DragDropEffects.Copy);
}
private void SelectedEmployees_Drop(object sender, System.Windows.DragEventArgs e)
{
// TODO: Add event handler implementation here.
var ems = e.Data.GetData(typeof(List<EmployeesItem>)) as List<EmployeesItem>;
if (ems == null)
return;
foreach(var em in ems)
{
SelectedEmployeeData.Add(em);
}
}
private void SelectedEmployees_DragOver(object sender, System.Windows.DragEventArgs e)
{
// TODO: Add event handler implementation here.
var ems = e.Data.GetData(typeof(List<EmployeesItem>)) as List<EmployeesItem>;
if (ems == null)
{
e.Effects = DragDropEffects.None;
return;
}
DragElement = ems[0];
e.Effects = DragDropEffects.Copy;
}3. 增加DataContext(ViewModel), 设置绑定的属性
public class EmployeeList : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public EmployeeList()
{
try
{
Uri resourceUri = new Uri("/WPFStudy;component/SampleData/EmployeeList/EmployeeList.xaml", UriKind.RelativeOrAbsolute);
System.Windows.Application.LoadComponent(this, resourceUri);
}
catch
{
}
}
private Employees _Employees = new Employees();
public Employees Employees
{
get
{
return this._Employees;
}
}
}
public class EmployeesItem : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public override bool Equals(object obj){var tmp = obj as EmployeesItem;if (tmp == null) return false;return tmp.Description.Equals(Description);}
private string _Description = string.Empty;
public string Description
{
get
{
return this._Description;
}
set
{
if (this._Description != value)
{
this._Description = value;
this.OnPropertyChanged("Description");
}
}
}
}
public class Employees : System.Collections.ObjectModel.ObservableCollection<EmployeesItem>
{
}