Occurs when the scroll box has been moved by either a mouse or keyboard action.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
The following example scrolls an image in a picture box. It uses the Value of the scrollbar to redraw a new part of the image whenever the user scrolls. This code example is part of a larger example provided for the ScrollBar class overview.
For instructions about how to run this example in Visual Studio, see How to: Compile and Run a Complete Windows Forms Code Example Using Visual Studio.
Private Sub HandleScroll(ByVal sender As [Object], ByVal e As ScrollEventArgs) _ Handles vScrollBar1.Scroll, hScrollBar1.Scroll 'Create a graphics object and draw a portion of the image in the PictureBox. Dim g As Graphics = pictureBox1.CreateGraphics() Dim xWidth As Integer = pictureBox1.Width Dim yHeight As Integer = pictureBox1.Height Dim x As Integer Dim y As Integer If (e.ScrollOrientation = ScrollOrientation.HorizontalScroll) Then x = e.NewValue y = vScrollBar1.Value Else 'e.ScrollOrientation == ScrollOrientation.VerticalScroll y = e.NewValue x = hScrollBar1.Value End If 'First Rectangle: Where to draw the image. 'Second Rectangle: The portion of the image to draw. g.DrawImage(pictureBox1.Image, _ New Rectangle(0, 0, xWidth, yHeight), _ New Rectangle(x, y, xWidth, yHeight), _ GraphicsUnit.Pixel) pictureBox1.Update() End Sub
The following code example uses the derived class VScrollBar. Event handlers for the and ValueChanged events are created. This code assumes that a Label and Button have been created on a form and that the button has an event handler for the Click event. When the button is clicked, the Value property of the scroll bar is adjusted in code. The label will display the current value of the Value property and the event that changed it. You will notice that when the scroll value is changed by the button's Click event, only the ValueChanged event is raised. In contrast, when the scroll bar is scrolled manually, the event is raised immediately after the ValueChanged event.
Private Sub AddMyScrollEventHandlers() ' Create and initialize a VScrollBar. Dim vScrollBar1 As New VScrollBar() ' Add event handlers for the OnScroll and OnValueChanged events. AddHandler vScrollBar1.Scroll, AddressOf Me.vScrollBar1_Scroll AddHandler vScrollBar1.ValueChanged, AddressOf Me.vScrollBar1_ValueChanged End Sub ' Create the ValueChanged event handler. Private Sub vScrollBar1_ValueChanged(sender As Object, e As EventArgs) ' Display the new value in the label. label1.Text = "vScrollBar Value:(OnValueChanged Event) " & _ vScrollBar1.Value.ToString() End Sub ' Create the Scroll event handler. Private Sub vScrollBar1_Scroll(sender As Object, e As ScrollEventArgs) ' Display the new value in the label. label1.Text = "VScrollBar Value:(OnScroll Event) " & _ e.NewValue.ToString() End Sub Private Sub button1_Click(sender As Object, e As EventArgs) ' Add 40 to the Value property if it will not exceed the Maximum value. If vScrollBar1.Value + 40 < vScrollBar1.Maximum Then vScrollBar1.Value = vScrollBar1.Value + 40 End If End Sub
Available since 1.1