Develop Reference

drag and drop winform controls

I want to drag and drop a control (label for example) in a winform application. I saw some examples on dragging and dropping text, but this is not what I want. I want to enable the user to move a control around. Can anyone direct me to some resources or examples? Thanks.

you should look at examples on how to make draggable controls.
There are some answers here in SO as well.
See this Move controls when Drag and drop on panel in C#
this is a complete example on how to host the Form Designer:
Tailor Your Application by Building a Custom Forms Designer with .NET
I did something similar in Delphi long time ago, will search the source code, convert it into .NET C# and make a wiki page on that matter, as it is becoming such popular question recently :)

As far as i understand, where you wish to drop a control is called a container, infact any control can act as a container. So first that container, you need to enable the drop property as well as the drag property of the controls which you need to drag.
Then write events (Candrag, candrop, controladded, etc.) for each control where in which, some logic to hold the objects and display them as you may want.
Say, ill take an example where in which, you wish to drag imagetext from combombox into a picturebox and then make the picturebox analyze the text and fine related file name in a directory and load that image into its if its present.
So here, when you start dragging the text from combombox, you have to write some logic in event candrag. Then once you drop, you have to write logic to understand what kinda object was added and get the text related to it (kinda deciphering) in the control where you drop other control.
Sorry, i have no code to give you now, but i hope you got the idea how its done. May be this article can help you? http://vicky4147.wordpress.com/2007/02/04/a-simple-drag-drop-in-winforms/

bool draging = false;
int curPosX, curPosY;
private void label2_MouseDown(object sender, MouseEventArgs e)
{
draging = true;
curPosX = Cursor.Position.X;
curPosY = Cursor.Position.Y;
}
private void label2_MouseMove(object sender, MouseEventArgs e)
{
if (draging)
{
label2.Left += Cursor.Position.X - curPosX;
curPosX = Cursor.Position.X;
label2.Top += Cursor.Position.Y - curPosY;
curPosY = Cursor.Position.Y;
}
}
private void label2_MouseUp(object sender, MouseEventArgs e)
{
draging = false;
}

C# Listview Drag and Drop Rows

I'm trying to implement a C# drag and drop row-reorder with a listview which would then update an SQL database with the current order of the rows. I've come across some snippets of code on the internet (one from this website which implemented a 'var' class) but none seem to be working with my needs. I don't need help updating the database as I have a good idea how I'd do this, but can't seem to get the row reordering to work correctly, any input would be appreciated.
-thanks
m&a

Ensure that AllowDragDrop is set to true.
Implement handlers for at least these 3 events
private void myList_ItemDrag(object sender, ItemDragEventArgs e)
{
DoDragDrop(e.Item, DragDropEffects.Link);
}
private void myList_DragEnter(object sender, DragEventArgs e)
{
e.Effect = DragDropEffects.Link;
}
private void myList_DragDrop(object sender, DragEventArgs e)
{
// do whatever you need to reorder the list.
}
Getting the index of the row you dropped onto may look something like:
Point cp = myList.PointToClient(new Point(e.X, e.Y));
ListViewItem dragToItem = myList.GetItemAt(cp.X, cp.Y);
int dropIndex = dragToItem.Index;

I know this isn't ListView specific, but I have sample code for implementing row drag and drop out of / into a DataGridView. Some of it is obviously control specific, other code is actually pretty generic (such as deciding when its a drag):
http://adamhouldsworth.blogspot.com/2010/01/datagridview-multiple-row-drag-drop.html
Completely forgot the fact that ListView already allows drag-dropping!
I can also add some theory - when the drop occurs on your control, you will need to hit test on those coordinates (likely a method called HitTest) on the ListView to see what row was hit, this is the basis for where to insert the row being dragged.
Unrelated - is that var class perhaps the new var keyword in C#?

WPF: Removing "yourself" from the parent container

I have a button in my user control which should be used to remove the user control from its parent container. This is the way I have coded it today.
private void RemoveRoleButton_Click(object sender, RoutedEventArgs e)
{
if (ConfirmRoleRemoval())
{
Panel parentPanel = (Panel)this.Parent;
parentPanel.Children.Remove(this);
}
}
private bool ConfirmRoleRemoval()
{
return MessageBox.Show("Are you sure [...]
}
Is it normal to do it this way in WPF?

Yes, it looks fine to me. As Mike Hillberg writes in his blog:
An element doesn’t actually pick its logical parent; instead, a parent “adopts” children.
Thus, it makes sense that "removing" a child is also done through the object model of the parent.
As a side note: You might want to consider throwing a "nice" exception (or even disabling the button) when the parent is not a Panel (rather than waiting for the InvalidCastException).

.NET: is there a Click-and-drag "Desktop-Like" control?

OK, first for context look at the Windows desktop; You can take items (folders, files) on the desktop and drag them around to different places and they "stay" where you dragged them. This seems to be a pretty useful feature to offer users so as to allow them to create their own "groupings" of items.
My question is thus:
Is there a control in .NET that approximates this behavior with a collection of items?
I'm thinking something like a listview in "LargeIcon" mode, but it allows you to drag the icons around to different places inside the control.

You can do this with a standard ListView control by implementing drag-and-drop. Here's a sample control that does this:
using System;
using System.Drawing;
using System.Windows.Forms;
public class MyListView : ListView {
private Point mItemStartPos;
private Point mMouseStartPos;
public MyListView() {
this.AllowDrop = true;
this.View = View.LargeIcon;
this.AutoArrange = false;
this.DoubleBuffered = true;
}
protected override void OnDragEnter(DragEventArgs e) {
if (e.Data.GetData(typeof(ListViewItem)) != null) e.Effect = DragDropEffects.Move;
}
protected override void OnItemDrag(ItemDragEventArgs e) {
// Start dragging
ListViewItem item = e.Item as ListViewItem;
mItemStartPos = item.Position;
mMouseStartPos = Control.MousePosition;
this.DoDragDrop(item, DragDropEffects.Move);
}
protected override void OnDragOver(DragEventArgs e) {
// Move icon
ListViewItem item = e.Data.GetData(typeof(ListViewItem)) as ListViewItem;
if (item != null) {
Point mousePos = Control.MousePosition;
item.Position = new Point(mItemStartPos.X + mousePos.X - mMouseStartPos.X,
mItemStartPos.Y + mousePos.Y - mMouseStartPos.Y);
}
}
}

I think the closest would the ListView control, but even that is more like an explorer window. You might be able to create your own view that does what you want, but you'd need to manually persist icon locations somewhere.

If you are not opposed to using WPF, Josh Smith has created a pretty neat canvas that I am currently using for a project. It allows you to add controls and drag them around the canvas. You would have to handle what is loaded on the canvas and where on the next load of the program, but that is pretty simple.
http://www.codeproject.com/KB/WPF/DraggingElementsInCanvas.aspx

This depends on whether this is a windows application or a web browser based application. In either case you need to have some sort of container to manage the locations of controls. You can manage the position of controls inside of a container with their X and Y coordinates.
You would handle the actual movement using the drag events. So you have drag start, while dragging (you might show a place holder graphic or change the cursor), and finally a drag end (set the control's x and y to the new position). Obviously these aren't the actual event names, but a search for "how to handle drag events" should get you started.
In a web environment, I know jquery has dragging capability built in. So you might want to look at that. The one big thing you'll have to be careful of is maintaining the positions of your controls between postbacks. I'm not sure what would happen in this case.

Windows uses ListView32, an internal control with drag n' drop placeholder features, custom borders...
The icon location can be stored in a XML file, or in the application settings (by putting the XML as string and converting it to file when needed).
You can do, for example:
<icons>
<icon1>
<name>Icon1</name>
<text>My PC</text>
<imageIndex>16</imageIndex>
</icon1>
<icon2>
.....
</icon2>
.....
</icons>
Lorenzo

How to implement the Edit -> Copy menu in c#/.net

How do I implement a Copy menu item in a Windows application written in C#/.NET 2.0?
I want to let the user to mark some text in a control and then select the Copy menu item from an Edit menu in the menubar of the application and then do a Paste in for example Excel.
What makes my head spin is how to first determine which child form is active and then how to find the control that contains the marked text that should be copied to the clipboard.
Help, please.

With the aid of some heavy pair programming a colleague of mine and I came up with this, feel free to refactor.
The code is placed in the main form. The copyToolStripMenuItem_Click method handles the Click event on the Copy menu item in the Edit menu.
/// <summary>
/// Recursively traverse a tree of controls to find the control that has focus, if any
/// </summary>
/// <param name="c">The control to search, might be a control container</param>
/// <returns>The control that either has focus or contains the control that has focus</returns>
private Control FindFocus(Control c)
{
foreach (Control k in c.Controls)
{
if (k.Focused)
{
return k;
}
else if (k.ContainsFocus)
{
return FindFocus(k);
}
}
return null;
}
private void copyToolStripMenuItem_Click(object sender, EventArgs e)
{
Form f = this.ActiveMdiChild;
// Find the control that has focus
Control focusedControl = FindFocus(f.ActiveControl);
// See if focusedControl is of a type that can select text/data
if (focusedControl is TextBox)
{
TextBox tb = focusedControl as TextBox;
Clipboard.SetDataObject(tb.SelectedText);
}
else if (focusedControl is DataGridView)
{
DataGridView dgv = focusedControl as DataGridView;
Clipboard.SetDataObject(dgv.GetClipboardContent());
}
else if (...more?...)
{
}
}

Why not extending the control, so the control itself provides the data which should be copied into the clipboard.
Take a look at ApplicationCommands documentation.

To determine which window is open, you can query the Form.ActiveMDIChild property to get a reference to the currently active window. From there, you can do one of two things:
1) If you create your own custom Form class (FormFoo for example) that has a new public member function GetCopiedData(), then inherit all of your application's child forms from that class, you can just do something like this:
((FormFoo)this.ActiveMDIChild).GetCopiedData();
Assuming the GetCopiedData function will have the form-specific implementation to detect what text should be copied to the clipboard.
or
2) You can use inheritance to detect the type of form that is active, and then do something to get the copied data depending on the type of form:
Form f = this.ActiveMDIChild;
if(f is FormGrid)
{
((FormGrid)f).GetGridCopiedData();
} else if(f is FormText) {
((FormText)f).GetTextCopiedData();
}
etc.
That should get you started with finding the active window and how to implement a copy function. If you need more help copying out of a GridView, it may be best to post another question.

If the form is tabbed and the target control is a DataGridView, it's sometimes possible for the Form's TabControl to be returned as the active control, using the above method, when the DataGridView is right clicked upon.
I got around this by implementing the following handler for my DataGridView:-
private void dataGridView_CellMouseDown(object sender, DataGridViewCellMouseEventArgs e)
{
if (e.Button == MouseButtons.Right)
{
dataGridView.Focus();
dataGridView.CurrentCell = dataGridView[e.ColumnIndex, e.RowIndex];
}
}

It seems to me that you might be better off breaking this into smaller tasks/questions.
You have a few issues you are stuck on from the way it sounds.
You have multiple 'child' windows open. Is this an MDI application?
When an action is performed on one of those child windows, it should fire an event in that window's event handlers. That is your first thing to set up. If this is a datagridview I would suggest a simple test to start. Try trapping the DataGridView.SelectionChanged event. Just throw in something like MessageBox.Show("I copied your datas!"); for now.
This should get you started where you will at least understand how this event will be raised to you.
From here, we will need to know a little more about your datagrid, and the rows and child controls in those rows. Then we can likely create events in the render events that will be raised at the appropriate times, with the appropriate scope.