Control.KeyDown Event and KeyEventArgs

Property	Description
Alt	Gets a value indicating whether the ALT key was pressed.
Control	Gets a value indicating whether the CTRL key was pressed.
Handled	Gets or sets a value indicating whether the event was handled.
KeyCode	Gets the keyboard code for a KeyDown or KeyUp event.
KeyData	Gets the key data for a KeyDown or KeyUp event.
KeyValue	Gets the keyboard value for a KeyDown or KeyUp event.
Modifiers	Gets the modifier flags for a KeyDown or KeyUp event. This indicates which combination of modifier keys (CTRL, SHIFT, and ALT) were pressed.
Shift	Gets a value indicating whether the SHIFT key was pressed.

Control.KeyDown:

Occurs when a key is pressed while the control has focus.

 

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

 

Remarks

---

Key events occur in the following order:

1. KeyDown

2. KeyPress

3. KeyUp

To handle keyboard events only at the form level and not enable other controls to receive keyboard events, set the KeyPressEventArgs.Handled property in your form's KeyPress event-handling method to true. Certain keys, such as the TAB, RETURN, ESCAPE, and arrow keys are handled by controls automatically. To have these keys raise the KeyDown event, you must override the IsInputKey method in each control on your form. The code for the override of the IsInputKey would need to determine if one of the special keys is pressed and return a value of true.

For more information about handling events, see Consuming Events.

Examples

---

The following code example uses the KeyDown event to determine the type of character entered into the control.

// Boolean flag used to determine when a character other than a number is entered. private bool nonNumberEntered = false; // Handle the KeyDown event to determine the type of character entered into the control. private void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e) { // Initialize the flag to false. nonNumberEntered = false; // Determine whether the keystroke is a number from the top of the keyboard. if (e.KeyCode < Keys.D0 || e.KeyCode > Keys.D9) { // Determine whether the keystroke is a number from the keypad. if (e.KeyCode < Keys.NumPad0 || e.KeyCode > Keys.NumPad9) { // Determine whether the keystroke is a backspace. if(e.KeyCode != Keys.Back) { // A non-numerical keystroke was pressed. // Set the flag to true and evaluate in KeyPress event. nonNumberEntered = true; } } } //If shift key was pressed, it's not a number. if (Control.ModifierKeys == Keys.Shift) { nonNumberEntered = true; } } // This event occurs after the KeyDown event and can be used to prevent // characters from entering the control. private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e) { // Check for the flag being set in the KeyDown event. if (nonNumberEntered == true) { // Stop the character from being entered into the control since it is non-numerical. e.Handled = true; } }

 

 

 

 

Gets the modifier flags for a KeyDown or KeyUp event. This indicates which combination of modifier keys (CTRL, SHIFT, and ALT) were pressed.

 

[C#]
public Keys Modifiers {get;}

 

Property Value

A Keys value representing one or more modifier flags.

Remarks

To determine whether a specific modifier key was pressed, use the Control, Shift, and Alt properties. Modifier flags can be combined with bitwise OR.

Example

[C#] // This example demonstrates how to use the KeyDown event with the Help class to display // pop-up style help to the user of the application. The example filters for all variations // of pressing the F1 key with a modifier key by using the KeyEventArgs properties passed // to the event handling method. // When the user presses any variation of F1 that includes any keyboard modifier, the Help // class displays a pop-up window, similar to a ToolTip, near the control. If the user presses // ALT + F2, a different Help pop-up is displayed with additional information. This example assumes // that a tTextBox control, named textBox1, has been added to the form and its KeyDown // event has been contected to this event handling method. private void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e) { // Determine whether the key entered is the F1 key. If it is, display Help. if(e.KeyCode == Keys.F1 && (e.Alt || e.Control || e.Shift)) { // Display a pop-up Help topic to assist the user. Help.ShowPopup(textBox1, "Enter your name.", new Point(textBox1.Bottom, textBox1.Right)); } else if(e.KeyCode == Keys.F2 && e.Modifiers == Keys.Alt) { // Display a pop-up Help topic to provide additional assistance to the user. Help.ShowPopup(textBox1, "Enter your first name followed by your last name. Middle name is optional.", new Point(textBox1.Top, this.textBox1.Left)); } }