TrackBar.Scroll Event

 

Occurs when either a mouse or keyboard action moves the scroll box.

Namespace:   System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

public event EventHandler Scroll

For more information about handling events, see Handling and Raising Events.

The following code example shows how to implement the Scroll event to modify information labels on a form, based on the scrolling of the scroll box on a track bar. The example requires a Form with three track bars and three labels placed on it.

private void showColorValueLabels()
{
    label1.Text = "Red value is : " + trackBar1.Value.ToString();
    label3.Text = "Green Value is : " + trackBar2.Value.ToString();
    label2.Text = "Blue Value is : " + trackBar3.Value.ToString();
}
private void trackBar_Scroll(object sender, System.EventArgs e)
{
    System.Windows.Forms.TrackBar myTB;
    myTB = (System.Windows.Forms.TrackBar) sender ;
    panel1.BackColor = Color.FromArgb(trackBar1.Value,trackBar2.Value,trackBar3.Value);
    myTB.Text = "Value is " + myTB.Value.ToString();
    showColorValueLabels();
}

The following code example displays a form that contains a TrackBar control and a TextBox control. The example demonstrates setting the Maximum, TickFrequency, LargeChange, and SmallChange properties and handling the Scroll event. The TextBox contents are updated to the Value property value when the Scroll event occurs.

using System;
using System.Drawing;
using System.Windows.Forms;

public class Form1 : System.Windows.Forms.Form
{
    private System.Windows.Forms.TrackBar trackBar1;
    private System.Windows.Forms.TextBox textBox1;

    [STAThread]
    static void Main() 
    {
        Application.Run(new Form1());
    }

    public Form1()
    {
        this.textBox1 = new System.Windows.Forms.TextBox();
        this.trackBar1 = new System.Windows.Forms.TrackBar();

        // TextBox for TrackBar.Value update.
        this.textBox1.Location = new System.Drawing.Point(240, 16);
        this.textBox1.Size = new System.Drawing.Size(48, 20);

        // Set up how the form should be displayed and add the controls to the form.
        this.ClientSize = new System.Drawing.Size(296, 62);
        this.Controls.AddRange(new System.Windows.Forms.Control[] {this.textBox1,this.trackBar1});
        this.Text = "TrackBar Example";

        // Set up the TrackBar.
        this.trackBar1.Location = new System.Drawing.Point(8, 8);
        this.trackBar1.Size = new System.Drawing.Size(224, 45);
        this.trackBar1.Scroll += new System.EventHandler(this.trackBar1_Scroll);

        // The Maximum property sets the value of the track bar when
        // the slider is all the way to the right.
        trackBar1.Maximum = 30;

        // The TickFrequency property establishes how many positions
        // are between each tick-mark.
        trackBar1.TickFrequency = 5;

        // The LargeChange property sets how many positions to move
        // if the bar is clicked on either side of the slider.
        trackBar1.LargeChange = 3;

        // The SmallChange property sets how many positions to move
        // if the keyboard arrows are used to move the slider.
        trackBar1.SmallChange = 2;
    }


    private void trackBar1_Scroll(object sender, System.EventArgs e)
    {
        // Display the trackbar value in the text box.
        textBox1.Text = "" + trackBar1.Value;
    }
}

.NET Framework
Available since 1.1
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