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MouseEventArgs.Delta Property

Gets a signed count of the number of detents the mouse wheel has rotated. A detent is one notch of the mouse wheel.

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

public int Delta { get; }

Property Value

Type: System.Int32
A signed count of the number of detents the mouse wheel has rotated.

The mouse wheel combines the features of a wheel and a mouse button. The wheel has discrete, evenly spaced notches. When you rotate the wheel, a wheel message is sent as each notch is encountered. One wheel notch, a detent, is defined by the windows constant WHEEL_DELTA, which is 120. A positive value indicates that the wheel was rotated forward, away from the user; a negative value indicates that the wheel was rotated backward, toward the user.

Currently, a value of 120 is the standard for one detent. If higher resolution mice are introduced, the definition of WHEEL_DATA might become smaller. Most applications should check for a positive or negative value rather than an aggregate total.

The following code example demonstrates the use of this member. In the example, an event handler reports on the occurrence of the Control.MouseClick event. This report helps you to learn when the event occurs and can assist you in debugging. To report on multiple events or on events that occur frequently, consider replacing MessageBox.Show with Console.WriteLine or appending the message to a multiline TextBox.

To run the example code, paste it into a project that contains an instance of a type that inherits from Control, such as a Button or ComboBox. Then name the instance Control1 and ensure that the event handler is associated with the Control.MouseClick event.

private void Control1_MouseClick(Object sender, MouseEventArgs e) {

System.Text.StringBuilder messageBoxCS = new System.Text.StringBuilder();
messageBoxCS.AppendFormat("{0} = {1}", "Button", e.Button );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "Clicks", e.Clicks );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "X", e.X );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "Y", e.Y );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "Delta", e.Delta );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "Location", e.Location );
messageBoxCS.AppendLine();
MessageBox.Show(messageBoxCS.ToString(), "MouseClick Event" );
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

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