true
表示跳过控件的默认处理;false
表示还将该事件传递给默认控件处理程序。
下面的示例确定用户是否按了非数值键,如果是,则 KeyPress 使用属性取消事件 Handled
// 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; } }