Control.BackColorChanged 事件
定义
重要
一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。 对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。
当 BackColor 属性的值更改时发生。
public:
event EventHandler ^ BackColorChanged;public event EventHandler BackColorChanged;public event EventHandler? BackColorChanged;member this.BackColorChanged : EventHandler Public Custom Event BackColorChanged As EventHandler 事件类型
示例
下面的代码示例是属性值更改时 Text 执行的事件处理程序。 类Control具有多个名称模式 PropertyName 的方法，这些方法在相应的 PropertyNameChanged 值更改时引发 (PropertyName 表示) 相应属性的名称。
下面的代码示例更改ForeColorTextBox显示货币数据的 。 该示例将文本转换为十进制数，如果数字为负数，则将 更改为 ForeColorColor.Red ;如果该数字为正数，则更改为 Color.Black 。 此示例要求具有 Form 包含 的 TextBox。
private:
void currencyTextBox_TextChanged( Object^ /*sender*/, EventArgs^ /*e*/ )
{
try
{
// Convert the text to a Double and determine if it is a negative number.
if ( Double::Parse( currencyTextBox->Text ) < 0 )
{
// If the number is negative, display it in Red.
currencyTextBox->ForeColor = Color::Red;
}
else
{
// If the number is not negative, display it in Black.
currencyTextBox->ForeColor = Color::Black;
}
}
catch ( Exception^ )
{
// If there is an error, display the text using the system colors.
currencyTextBox->ForeColor = SystemColors::ControlText;
}
}
private void currencyTextBox_TextChanged(object sender, EventArgs e)
{
try
{
// Convert the text to a Double and determine if it is a negative number.
if(double.Parse(currencyTextBox.Text) < 0)
{
// If the number is negative, display it in Red.
currencyTextBox.ForeColor = Color.Red;
}
else
{
// If the number is not negative, display it in Black.
currencyTextBox.ForeColor = Color.Black;
}
}
catch
{
// If there is an error, display the text using the system colors.
currencyTextBox.ForeColor = SystemColors.ControlText;
}
}
Private Sub currencyTextBox_TextChanged(sender As Object, _
e As EventArgs) Handles currencyTextBox.TextChanged
Try
' Convert the text to a Double and determine if it is a negative number.
If Double.Parse(currencyTextBox.Text) < 0 Then
' If the number is negative, display it in Red.
currencyTextBox.ForeColor = Color.Red
Else
' If the number is not negative, display it in Black.
currencyTextBox.ForeColor = Color.Black
End If
Catch
' If there is an error, display the text using the system colors.
currencyTextBox.ForeColor = SystemColors.ControlText
End Try
End Sub
注解
如果通过编程修改或用户交互更改属性， BackColor 则会引发此事件。
有关处理事件的详细信息，请参阅 处理和引发事件。
