TrackBar.ValueChanged Event

Definition

Namespace:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Source:

TrackBar.cs

Occurs when the Value property of a track bar changes, either by movement of the scroll box or by manipulation in code.

public:
 event EventHandler ^ ValueChanged;

public event EventHandler? ValueChanged;

member this.ValueChanged : EventHandler 

Public Custom Event ValueChanged As EventHandler 

Event Type

EventHandler

Examples

The following code example demonstrates how to use the TickStyle, Minimum, and Maximum members and how to handle the ValueChanged event. To run the example, paste the following code into a form that contains a TrackBar control name TrackBar1 and a TextBox control named TextBox1. Call the InitializeTrackBar method from the form's constructor or Load event-handling method.

   //Declare a new TrackBar object.
internal:
   System::Windows::Forms::TrackBar^ TrackBar1;

   // Initialize the TrackBar and add it to the form.
private:
   void InitializeTrackBar()
   {
      this->TrackBar1 = gcnew System::Windows::Forms::TrackBar;
      TrackBar1->Location = System::Drawing::Point( 75, 30 );
      
      // Set the TickStyle property so there are ticks on both sides
      // of the TrackBar.
      TrackBar1->TickStyle = TickStyle::Both;
      
      // Set the minimum and maximum number of ticks.
      TrackBar1->Minimum = 10;
      TrackBar1->Maximum = 100;
      
      // Set the tick frequency to one tick every ten units.
      TrackBar1->TickFrequency = 10;
      
      // Associate the event-handling method with the 
      // ValueChanged event.
      TrackBar1->ValueChanged += gcnew System::EventHandler( this, &Form1::TrackBar1_ValueChanged );
      this->Controls->Add( this->TrackBar1 );
   }

   // Handle the TrackBar.ValueChanged event by calculating a value for
   // TextBox1 based on the TrackBar value.  
   void TrackBar1_ValueChanged( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      TextBox1->Text = (System::Math::Round( TrackBar1->Value / 10.0 )).ToString();
   }

//Declare a new TrackBar object.
internal System.Windows.Forms.TrackBar TrackBar1;

// Initialize the TrackBar and add it to the form.
private void InitializeTrackBar()
{
    this.TrackBar1 = new System.Windows.Forms.TrackBar();
    TrackBar1.Location = new System.Drawing.Point(75, 30);

    // Set the TickStyle property so there are ticks on both sides
    // of the TrackBar.
    TrackBar1.TickStyle = TickStyle.Both;

    // Set the minimum and maximum number of ticks.
    TrackBar1.Minimum = 10;
    TrackBar1.Maximum = 100;

    // Set the tick frequency to one tick every ten units.
    TrackBar1.TickFrequency = 10;

    // Associate the event-handling method with the 
    // ValueChanged event.
    TrackBar1.ValueChanged += 
        new System.EventHandler(TrackBar1_ValueChanged);
    this.Controls.Add(this.TrackBar1);
}

// Handle the TrackBar.ValueChanged event by calculating a value for
// TextBox1 based on the TrackBar value.  
private void TrackBar1_ValueChanged(object sender, System.EventArgs e)
{
    TextBox1.Text = (System.Math.Round(TrackBar1.Value/10.0)).ToString();
}

'Declare a new TrackBar object.
Friend WithEvents TrackBar1 As System.Windows.Forms.TrackBar

' Initialize the TrackBar and add it to the form.
Private Sub InitializeTrackBar()
    Me.TrackBar1 = New System.Windows.Forms.TrackBar

    ' Set the TickStyle property so there are ticks on both sides
    ' of the TrackBar.
    TrackBar1.TickStyle = TickStyle.Both

    ' Set the minimum and maximum number of ticks.
    TrackBar1.Minimum = 10
    TrackBar1.Maximum = 100

    ' Set the tick frequency to one tick every ten units.
    TrackBar1.TickFrequency = 10

    TrackBar1.Location = New System.Drawing.Point(75, 30)
    Me.Controls.Add(Me.TrackBar1)
End Sub


' Handle the TrackBar.ValueChanged event by calculating a value for
' TextBox1 based on the TrackBar value.  
Private Sub TrackBar1_ValueChanged(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles TrackBar1.ValueChanged
    TextBox1.Text = System.Math.Round(TrackBar1.Value / 10)
End Sub

Remarks

You can use this event to update other controls when the value represented in the track bar changes.

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