Drag Tools Overview

In This Topic

All drag operations inherit directly or indirectly from the NDragTool class, which suggests that they share a number of common features.

Selection

All drag tools depend on the current selection. As we mentioned in the Selection topic the selection can be modified both programmatically and visually (by the user).

Events

All drag tools raise the BeginDrag, DoDrag, EndDrag and Cancel events. Their meaning and paramters are described in the following table:

Event	Description	Event argument
BeginDrag	Fired before a drag operation is about to begin.	An object of type NDragEventArgs containg the mouse coordinates as well as the current key state.
Drag	Fired when a drag operation is being processed.	An object of type NDragEventArgs containg the mouse coordinates as well as the current key state.
EndDrag	Fired after a drag operation has ended.	An object of type NDragEventArgs containg the mouse coordinates as well as the current key state.
Cancel	Fired if the user pressed the Escape button.	A null (Nothing in VB.NET) value.

You subscribe to these events in the following manner:

C#	Copy Code
someDragTool.BeginDrag += new EventHandler(OnSomeDragToolBeginDrag); someDragTool.EndDrag += new EventHandler(OnSomeDragToolEndDrag); someDragTool.Drag += new EventHandler(OnSomeDragToolDoDrag); someDragTool.Cancel += new EventHandler(OnSomeDragToolCancel);

Copy Code

someDragTool.BeginDrag += new EventHandler(OnSomeDragToolBeginDrag);
someDragTool.EndDrag += new EventHandler(OnSomeDragToolEndDrag);
someDragTool.Drag += new EventHandler(OnSomeDragToolDoDrag);
someDragTool.Cancel += new EventHandler(OnSomeDragToolCancel);

Visual Basic	Copy Code
AddHandler someDragTool.BeginDrag, AddressOf OnSomeDragToolBeginDrag AddHandler someDragTool.EndDrag, AddressOf OnSomeDragToolEndDrag AddHandler someDragTool.Drag, AddressOf OnSomeDragToolDoDrag AddHandler someDragTool.Cancel, AddressOf OnSomeDragToolCancel

Visual Basic

Copy Code

AddHandler someDragTool.BeginDrag, AddressOf OnSomeDragToolBeginDrag
AddHandler someDragTool.EndDrag, AddressOf OnSomeDragToolEndDrag
AddHandler someDragTool.Drag, AddressOf OnSomeDragToolDoDrag
AddHandler someDragTool.Cancel, AddressOf OnSomeDragToolCancel

Cancelling Drag Operations

All drag operations can be cancelled by the user when he/she presses the Esc key. In addition you can programmatically terminate a drag operation by calling the Cancel method of NDragTool class.

Changing the Mouse Drag Button

Most of the drag operations are activated when the user presses the left mouse button and drags the mouse over the chart. An exception to this is the NDataPanTool drag tool which is activated when the user presses the right mouse button key. You can control the mouse action that triggers the drag operation by modifying the BeginDragMouseCommand property of the NDragTool object. The following code will create a trackball tool activated when the user presses the right mouse button:

C#	Copy Code
NTrackballTool trackballTool = new NTrackballTool(); trackballTool.BeginDragMouseCommand = new NMouseCommand(MouseAction.Down, MouseButtons.Right, 1); chartControl.Controller.Tools.Add(trackballTool);

Visual Basic	Copy Code
Dim trackballTool As New NTrackballTool trackballTool.BeginDragMouseCommand = New NMouseCommand(MouseAction.Down, MouseButtons.Right, 1) chartControl.Controller.Tools.Add(trackballTool)

Changing the Mouse Cursor

The mouse cursor associated with each drag operation can be modified with the help of the Cursor property of the NDragTool object:

C#	Copy Code
someDragTool.Cursor = Cursors.Hand;

Visual Basic	Copy Code
someDragTool.Cursor = Cursors.Hand