ScrollBarBase.Scroll Event

Fires when the scroll thumb has been moved either by a mouse or keyboard action.

Namespace: DevExpress.XtraEditors

Assembly: DevExpress.Utils.v20.1.dll

Declaration

[DXCategory("Action")]
public event ScrollEventHandler Scroll
<DXCategory("Action")>
Public Event Scroll As ScrollEventHandler

Event Data

The Scroll event's data class is ScrollEventArgs. The following properties provide information specific to this event:

Property Description
NewValue Gets or sets the new Value of the scroll bar.
OldValue Gets the old Value of the scroll bar.
ScrollOrientation Gets the scroll bar orientation that raised the Scroll event.
Type Gets the type of scroll event that occurred.

Remarks

When the Scroll event is raised, the ScrollBarBase.Value property is set automatically to a value corresponding to the scroll box's new position.

Note: changing the ScrollBarBase.Value property via code doesn't raise the Scroll event.

Examples

The following sample code uses both HScrollBar and VScrollBar controls to provide easy navigation through an image displayed within the pictureBox control if image dimensions extend the dimensions of the picture box. The Paint picture box event is handled to draw a specific image region specified by the position of the scroll bar to the screen. The x and y variables correspondingly represent the x- and y-coordinate of the upper-left corner of the portion of the image to draw in the picture box. The ScrollBarBase.Scroll events are used, in turn, to define the coordinates of the upper-left corner of the image portion according to scroll bar position after the user has scrolled either one or both scroll bars.

ScrollBar - events

using DevExpress.XtraEditors;
private void Form1_Load(object sender, System.EventArgs e) {
   hScrollBar1.Width = pictureBox1.Width;
   hScrollBar1.Left = pictureBox1.Left;
   hScrollBar1.Top = pictureBox1.Bottom;
   hScrollBar1.Maximum = pictureBox1.Image.Width - pictureBox1.Width;
   vScrollBar1.Height = pictureBox1.Height;
   vScrollBar1.Left = pictureBox1.Left + pictureBox1.Width;
   vScrollBar1.Top = pictureBox1.Top;
   vScrollBar1.Maximum = pictureBox1.Image.Height - pictureBox1.Height;
}

int x = 0;
private void hScrollBar1_Scroll(object sender, System.Windows.Forms.ScrollEventArgs e) {
   x = (sender as HScrollBar).Value;
   pictureBox1.Refresh();
}

int y = 0;
private void vScrollBar1_Scroll(object sender, System.Windows.Forms.ScrollEventArgs e) {
   y = (sender as VScrollBar).Value;
   pictureBox1.Refresh();
}
private void pictureBox1_Paint(object sender, System.Windows.Forms.PaintEventArgs e) {
   pBox = sender as PictureBox;
   e.Graphics.DrawImage(pBox.Image, e.ClipRectangle, x, y, e.ClipRectangle.Width, 
     e.ClipRectangle.Height, GraphicsUnit.Pixel);
}
See Also