How can I set the width of a listbox to fit the text
You can iterate through the list to find the longest text extent using MeasureString, adding a fudge factor if the scrollbar is present. System.Drawing.Graphics g = listBox1.CreateGraphics(); float maxWidth = 0f; float height = 0f; for (int i = 0; i < listBox1.Items.Count; ++i) { float w = g.MeasureString(listBox1.Items[i].ToString(), listBox1.Font).Width; if (w > maxWidth) maxWidth = w; height += listBox1.GetItemHeight(i); } g.Dispose(); listBox1.Width = (int) (maxWidth + 6 + ((height > listBox1.Height – 4) ? 16 : 0)); // 16 is scrollbar width
How can I make my control automatically grow when the parent form is sized
Change the control’s Anchor property so that it is anchored on all 4 sides. Please note that you can only have 1 control per form anchored in this manner (all 4 sides). And other controls on the form should be anchored by their sides that are not adjacent to special control anchored on all 4 sides.
How do I implement Drag and Drop support between ListBoxes
The code below minimally handles D&D for a single selection list box by handling four events. The D&D is initiated in MouseDown if the user mouses down on the current selection. The DragEnter event is used to set the dragging effect to copy if you are not over the drag source. The DragDrop event is used to do the drop. And finally, the SelectedIndexChanged event is used to track the current selection for use in the MouseDown event. You can download a working project (C#, VB). This project handles additional events to provide visual queues during the drop. The samples referenced above do not allow dragging and dropping within the same listbox. Here is another set of samples that does allow you to drag and drop within the same listbox. public class ListBoxDragNDrop : ListBox { private int lastMouseUpItemIndex = -1; private bool isDropSource = false; public ListBoxDragNDrop() { this.AllowDrop = true; //allow D&D this.SelectionMode = SelectionMode.One; //single selection DragDrop += new System.Windows.Forms.DragEventHandler(OnDragDrop); DragEnter += new System.Windows.Forms.DragEventHandler(OnDragEnter); MouseDown += new System.Windows.Forms.MouseEventHandler(OnMouseDown); SelectedIndexChanged += new System.EventHandler(OnSelectedIndexChanged); } private void OnDragDrop(object sender, DragEventArgs e) { if(e.Effect == DragDropEffects.Copy) { Point point = this.PointToClient(new Point(e.X, e.Y)); int index = this.IndexFromPoint(point); if( index > -1 && index < this.Items.Count) Items.Insert(index, e.Data.GetData(DataFormats.Text)); else Items.Add(e.Data.GetData(DataFormats.Text)); } } private void OnDragEnter(object sender, System.Windows.Forms.DragEventArgs e) { if (e.Data.GetDataPresent(DataFormats.Text) && !isDropSource ) e.Effect = DragDropEffects.Copy; else e.Effect = DragDropEffects.None; } private void OnMouseDown(object sender, System.Windows.Forms.MouseEventArgs e) { if(MouseButtons == MouseButtons.Left && SelectedIndex == lastMouseUpItemIndex) { isDropSource = true; DoDragDrop(SelectedItem, DragDropEffects.Copy); isDropSource = false; lastMouseUpItemIndex = this.SelectedIndex; } } private void OnSelectedIndexChanged(object sender, System.EventArgs e) { lastMouseUpItemIndex = this.SelectedIndex; } } One more note. If your listboxes contain full file pathnames, you can support dropping these paths onto Windows Explorer by supporting the FileDrop dataformat. In the OnMouseDown override, if you replace the DoDragDrop line with the following code block, you will be able to drop files. //put the file path is a string array string[] files = new String[1]; files[0] = SelectedItem.ToString(); //create a dataobject holding this array as a filedrop DataObject data = new DataObject(DataFormats.FileDrop, files); //also add the selection as textdata data.SetData(DataFormats.StringFormat, SelectedItem.ToString()); //do the dragdrop DoDragDrop(data, DragDropEffects.Copy);
How can I drag file names from Windows Explorer and drop them into a listbox
Place a ListBox on your form, set its AllowDrop property and handle both DragEnter and DragDrop as below. private void listBox1_DragEnter(object sender, System.Windows.Forms.DragEventArgs e) { if (e.Data.GetDataPresent(DataFormats.FileDrop)) e.Effect = DragDropEffects.All; else e.Effect = DragDropEffects.None; } private void listBox1_DragDrop(object sender, System.Windows.Forms.DragEventArgs e) { string[] files = (string[])e.Data.GetData(‘FileDrop’, false); foreach (string s in files) { //just filename listBox1.Items.Add(s.Substring(1 + s.LastIndexOf(@’\’))); //or fullpathname // listBox1.Items.Add(s); } }
How come I don’t get to see the full call stack while debugging in VS2003?
In VS2003, debug info for unmanaged code is turned off by default. This is why you will not see the call stack including code in the System dlls. To enable debugging for unmanaged code go to your project properties dialog and turn on as shown in the image below: Fig: Turning On Unmanaged code debugging