WPF Datagrid 拖放问题答案

【问题标题】：WPF Datagrid drag and drop questionsWPF Datagrid 拖放问题
【发布时间】：2011-08-14 20:47:34
【问题描述】：

我有一个 WPF Datagrid，我正在实现拖放功能。
数据网格有一个“文件”列表，用户可以拖动它们并将文件复制到桌面。
这样做是这样的：

string[] files = new String[myDataGrid.SelectedItems.Count];
int ix = 0;
foreach (object nextSel in myDataGrid.SelectedItems)
{
    files[ix] = ((Song)nextSel).FileLocation;
    ++ix;
}
string dataFormat = DataFormats.FileDrop;
DataObject dataObject = new DataObject(dataFormat, files);
DragDrop.DoDragDrop(this.myDataGrid, dataObject, DragDropEffects.Copy);

我有两个问题：
1.当我想拖动多个项目时-这是一个问题，因为在我选择了一对并开始单击一个开始拖动后-只有那个被选中而其他项目被取消选择。我尝试了here 给出的解决方案，但由于某种原因它不起作用。
2.我想在复制后将拖动的项目从数据网格中删除。问题是我不知道如何检查文件是否被复制，或者用户是否只是在屏幕上拖动它而不复制它。

希望你能帮我解决这些问题。
谢谢！

【问题讨论】：

标签： wpf drag-and-drop wpfdatagrid

【解决方案1】：

我想这就是你要找的东西：

将此代码添加到 DataGrid__PreviewMouseLeftButtonDown 事件处理程序：

private void DataGrid_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    this.startingPosition = e.GetPosition(null);

    DependencyObject dep = (DependencyObject)e.OriginalSource;

    // iteratively traverse the visual tree until get a row or null
    while ((dep != null) && !(dep is DataGridRow))
    {
        dep = VisualTreeHelper.GetParent(dep);
    }

    //if this is a row (item)
    if (dep is DataGridRow)
    {
        //if the pointed item is already selected do not reselect it, so the previous multi-selection will remain
        if (songListDB.SelectedItems.Contains((dep as DataGridRow).Item))
        {
            // now the drag will drag all selected files
            e.Handled = true;
        }
    }
}

现在拖动不会改变你的选择。

祝你好运！

我用article 写了我的答案

【讨论】：

谢谢！正是我想要的 [songListDB? :) ]
这是迄今为止我见过的最简单的解决方案。谢谢。

【解决方案2】：

改进了查找行。在不拖动时还选择单击的行。现在，它的行为与其他 Microsoft 选择器（例如 Outlook）完全相同

    public TreeDataGrid()
    {
        Loaded += TreeDataGrid_Loaded;
        LoadingRow += new EventHandler<DataGridRowEventArgs>(TreeDataGrid_LoadingRow);
    }

    #region MultiSelect Drag

    object toSelectItemOnMouseLeftButtonUp;

    void TreeDataGrid_LoadingRow(object sender, DataGridRowEventArgs e)
    {
        e.Row.PreviewMouseLeftButtonDown += new MouseButtonEventHandler(Row_PreviewMouseLeftButtonDown);
        e.Row.PreviewMouseLeftButtonUp += new MouseButtonEventHandler(Row_PreviewMouseLeftButtonUp); 
    }

    void Row_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        DataGridRow row = (DataGridRow)sender;
        toSelectItemOnMouseLeftButtonUp = null; // always clear selecteditem 
        if (SelectedItems.Contains(row.Item))  //if the pointed item is already selected do not reselect it, so the previous multi-selection will remain
        {
            e.Handled = true;  // this prevents the multiselection from disappearing, BUT datagridcell still gets the event and sets DataGrid's private member _selectionAnchor
            toSelectItemOnMouseLeftButtonUp = row.Item; // store our item to select on MouseLeftButtonUp
        }
    }

    void Row_PreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        DataGridRow row = (DataGridRow)sender; 
        if (row.Item == toSelectItemOnMouseLeftButtonUp)  // check if it's set and concerning the same row
        {
            if (SelectedItem == toSelectItemOnMouseLeftButtonUp) SelectedItem = null;  // if the item is already selected whe need to trigger a change 
            SelectedItem = toSelectItemOnMouseLeftButtonUp;  // this will clear the multi selection, and only select the item we pressed down on
            typeof(DataGrid).GetField("_selectionAnchor", BindingFlags.Instance | BindingFlags.NonPublic).SetValue(this, new DataGridCellInfo(row.Item, ColumnFromDisplayIndex(0)));  // we need to set this anchor for when we select by pressing shift key
            toSelectItemOnMouseLeftButtonUp = null;  // handled
        }
    }

    #endregion

【讨论】：