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WinForms pass through clicks to controls below another

I have a following form in WinForms as a prototype for a game:
GestureControl is a transparent Control that handles its MouseDown and MouseUp events to allow for swiping gestures. Then there are SquareControls (game pieces) that should be clickable as well.
I'm not sure how to arrange these controls so both
SquareControl will receive Click event
GestureControl will receive MouseDown and MouseUp events
I know I could add a Click Gesture to my GestureControl (when the distance between mouse down and mouse up is not far away), pass it to parent and invoke the same event handler as if the corresponding SquareControl was clicked, but this seems hackish.

How to prevent mouse leave event when hovering over checkbox

I have a form with the panel, which will have some checkboxes for options. I made panel slide in to the form when mouse hovers the edge of it (edge of panel). I made it hide (slide back) when mouse leaves the panel. The problem is that when I point a checkbox in this panel a mouseleave event occures and panel slides back so I cannot check checkbox. Is there any way to prevent mouseleave event when mouse is still over the panel and some checkboxes in it? My idea for know is to make a condition based on mouse pointer position in mouseleave event, but I hope that there is a way to make app treat a checkbox as a part of panel. Did not put any food since it is not problem of it. But can post if needed.

What happens here is that the mouseleave event of the checkbox triggers mouseleave event of the panel due to the event bubbling. You can read more about event bubbling here.
To prevent the event bubbling, attach mouseleave event on the checkboxes and call event.stopPropagation().
Sample code with jQuery:
$("checkboxes_selector").on("mouseleave", function(event){
event.stopPropagation();
});

WPF Touch up event in Microsoft surface still calls even I dragg my finger out of the area

I am writing an event for a textBox_Touch_up. And I want if user Touch Up on the text box then fire this event but if user dragged his finger somewhere out of the textbox and then touch up then this event should not be called. Is there any other event with which I can do it or I Have to play with it ?

The touch_up Event does not provide similar functionality for Textboxes because Textboxes contain text. So I used a flat button and it works for me as it does not fire the event when i drag my finger out of it.

DragLeave event is firing in loop

I'm implementing drag and drop functionality.
I just wanted to add element to ObservableCollection when drag enters and mouse is over the canvas and remove from ObservableCollection when drag leaves the canvas.
Unfortunately DragLeave and DragEnter is firing constantly even if the cursor is over canvas and I do not move it. Why it happens?

How can I detect a held down mouse button over a PictureBox?

I need to fire an event when the mouse is above a PictureBox with the mouse button already clicked and held down.
Problems:
The MouseDown and MouseEnter event handlers do not work together very well.
For instance once a mouse button is clicked and held down, C# will fire the MouseDown event handler, but when the cursor moves over the PictureBox the MouseEnter event does not fire, until the mouse button is realeased.

When the mouse is pressed down most controls will then Control.Capture the mouse input. This means that all MouseMove events are sent to the original control that captured rather than the control the mouse happens to be over. This continues until the mouse loses capture which typically happens on the mouse up.
If you really need to know when the mouse is over your control even when another control has captured mouse input then you only really have one way. You need to snoop the windows messages destined for other controls inside your application. To do that you need add a message filter ...
Application.AddMessageFilter(myFilterClassInstance);
Then you need to implement the IMessageFilter on a suitable class...
public class MyFilterClass : IMessageFilter
{
public bool PreFilterMessage(ref Message m)
{
if (m.Msg == WM_MOUSEMOVE)
// Check if mouse is over my picture box!
return false;
}
}
Then you watch for mouse move events and check if they are over your picture box and do whatever it is you want to do.

Mouse events
Use the MouseDown event to just detect a down press of a mouse button and set this.Capture to true so that you then get other mouse events, even when the mouse leaves the control (i.e. you won't get a MouseLeave event because you captured the mouse). Release capture by setting this.Capture to false when MouseUp occurs.
Just checking the state of the mouse
This may not be relevant, but you can check System.Windows.Control.MousePosition and see if it is in the PictureBox.ClientRectangle, then check the Control.MouseButtons static property for which buttons might be down at any time.
As in:
if (pictureBox.ClientRectangle.Contains(pictureBox.PointToClient(Control.MousePosition)))
{
if ((Control.MouseButtons & MouseButtons.Left) != 0)
{
// Left button is down.
}
}

Set up a MouseMove event within the PictureBox control:
this.myPictureBox.MouseMove += new System.Windows.Forms.MouseEventHandler(this.myPictureBox_MouseMove);
Then, within your MouseMove event handler, check to see if the left mouse button (or whatever) is pressed:
private void myPictureBox_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
// Do what you want to do
}

If you're trying to implement a drag-and-drop operation of some sort, the Drag... events (DragEnter, DragDrop etc.) on the receiving picture box are what you want to use. Basically, you start the drag operation using the DoDragDrop method of the source control, and then any control that you drag over will have its Drag... events raised.
Search "DoDragDrop" on MSDN to see how to implement this.

You can use the Preview Events
For example say I want to detect a mousedown event on my button. The MouseDown event is not going to work because as one of the answers here, the mouse capture is sent to the main control, however what you can do is use the mouse preview event.
Here is a code example
I want to check when the Left Mouse Button is pressed on my Button, hence I use the PreviewMouseLeftButtonDown
private void MyButton_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
// code here
}
WPF has preview events for alot of other events, you can read about them here
Preview Events - It particular talks about Buttons and how the mouse events interacts with it, So I highly recommend you read it

The best way to move a Form based on mouse position and control relative position is similar to what Ian Campbell posted.
private void imgMoveWindow_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
Form1.ActiveForm.Left = Control.MousePosition.X - imgMoveWindow.Left - (imgMoveWindow.Size.Width/2);
Form1.ActiveForm.Top = Control.MousePosition.Y - imgMoveWindow.Top - (imgMoveWindow.Size.Height/2);
}
}
Where imgMoveWindow is a PictureBox Control.
Bruno Ratnieks
Sniffer Networks

You should try MouseMove of the picture box instead of MouseEnter, MouseMove will normally fire regardless mouse button state.

set a flag or a state on mouse down. release it on mouse up.
When on mouse over fires for the picture box check your state.
Now you can detect when a person is dragging something.