แก้ไข

แชร์ผ่าน

DependencyObject.CoerceValue(DependencyProperty) Method

  • Reference

Definition

Namespace:
System.Windows
Assembly:
WindowsBase.dll

Coerces the value of the specified dependency property. This is accomplished by invoking any CoerceValueCallback function specified in property metadata for the dependency property as it exists on the calling DependencyObject.

public:
 void CoerceValue(System::Windows::DependencyProperty ^ dp);
public void CoerceValue (System.Windows.DependencyProperty dp);
member this.CoerceValue : System.Windows.DependencyProperty -> unit
Public Sub CoerceValue (dp As DependencyProperty)

Parameters

dp
DependencyProperty

The identifier for the dependency property to coerce.

Exceptions

InvalidOperationException

The specified dp or its value were invalid or do not exist.

Examples

The following example calls CoerceValue within a PropertyChangedCallback implementation that is used as the PropertyChangedCallback for a different dependency properties on the same class. This is a common pattern for introducing true value dependencies between dependency properties.

private static void OnCurrentReadingChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
  d.CoerceValue(MinReadingProperty);
  d.CoerceValue(MaxReadingProperty);
}

Private Shared Sub OnCurrentReadingChanged(ByVal d As DependencyObject, ByVal e As DependencyPropertyChangedEventArgs)
    d.CoerceValue(MinReadingProperty)
    d.CoerceValue(MaxReadingProperty)
End Sub

Remarks

In addition to being explicitly invoked through calling CoerceValue, the CoerceValueCallback for a dependency property is also invoked internally whenever the dependency property value is being re-evaluated by the WPF property system.

When you invoke the CoerceValue method, you are ultimately invoking the coerce value callback for the property that you specify. Typically you will invoke CoerceValue only if you know that a coerce value callback exists, and if you know the callback's criteria for coercion.

The most common scenario for calling CoerceValue is within class handling or property change callbacks of related properties that influence each other's values in a dependent way. For more information, see Dependency Property Callbacks and Validation.

Applies to

See also