Question

我有一个WPF Datagrid，我正在实现拖放功能 datagrid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是这样做的：

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，因为在我选择一对并开始点击其中一个开始拖动之后 - 仅选择该项目并取消选择其他项目。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.我希望在复制后从数据网格中删除拖动的项目。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。

我希望你能帮助我解决这些问题谢谢！

Answer 1

我认为这就是你要找的东西：

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

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，拖延不会改变你的选择。

祝你好运！

我用article来写我的答案

Answer 2

改进了查找行。还添加了在不拖动时选择单击的行。现在，这与其他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

WPF Datagrid拖放问题

2 个答案: