Control.BackgroundImageChanged 事件
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
發生於 BackgroundImage 屬性的值變更時。
public:
event EventHandler ^ BackgroundImageChanged;public event EventHandler BackgroundImageChanged;public event EventHandler? BackgroundImageChanged;member this.BackgroundImageChanged : EventHandler Public Custom Event BackgroundImageChanged As EventHandler 事件類型
範例
下列程式碼範例是屬性值變更時 Text 所執行的事件處理常式。 類別 Control 有數個名稱模式PropertyNameChanged 的方法，當對應的PropertyName值變更 (PropertyName代表對應屬性的名稱) 時引發。
下列程式碼範例會變更 ForeColorTextBox 顯示貨幣資料的 。 本範例會將文字轉換成十進位數，如果數位為負數，則變更為 ，如果 Color.Black 數位為正數，則為 。 ForeColorColor.Red 此範例需要您有 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
備註
如果屬性是透過程式設計修改或使用者互動來變更，就會 BackgroundImage 引發這個事件。
如需處理事件的詳細資訊，請參閱 處理和引發事件。
