Control.OnKeyPress(KeyPressEventArgs) 方法

定义

命名空间:

System.Windows.Forms

程序集:

System.Windows.Forms.dll

Source:

Control.cs

引发 KeyPress 事件。

C#

protected virtual void OnKeyPress(System.Windows.Forms.KeyPressEventArgs e);

参数

e

KeyPressEventArgs

包含事件数据的 KeyPressEventArgs。

示例

下面的代码示例使用 KeyPress 事件来防止字符进入控件。

C#

// 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)
    {
        // Stop the character from being entered into the control since it is non-numerical.
        e.Handled = true;
    }
}

注解

引发事件时，将通过委托调用事件处理程序。 有关详细信息，请参阅 处理和引发事件。

OnKeyPress 方法还允许派生类对事件进行处理而不必附加委托。 这是在派生类中处理事件的首选技术。

继承者说明

在派生类中重写 OnKeyPress(KeyPressEventArgs) 时，一定要调用基类的 OnKeyPress(KeyPressEventArgs) 方法，以便已注册的委托对事件进行接收。

适用于

另请参阅

• KeyPress