WPF Datagrid drag and drop questions

Question

I have Datagrid WPF and I am implementing drag and drop functions.
There is a list of “files” in the datagrid, and the user can drag them and copy the file to the desktop.
This is done as follows:

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); 

I have two questions:
1. When I want to drag a few elements - this is a problem, because after I select a pair and start clicking on it to start the drag, which will be selected, and the rest of the elements will be canceled. I tried the solution given here , but for some reason it does not work.
2. I want to remove the dragged item from the datagrid after copying it. The problem is that I don’t know how to check if the file was copied or the user simply dragged it onto the screen without copying it.

Hope you can help me solve these problems. Thanks!

Answer 1

I think this is what you are looking for:

add this code to the DataGrid__PreviewMouseLeftButtonDown event handler:

 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; } } } 

and now casting will not change your choice.

Good luck

I used the article to write my answer

Answer 2

Improved when searching for a string. Also choosing clicking a row when not dragging. Now it behaves just like other Microsoft selectors (e.g. Outlook)

  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 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 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