PropertyMetadata.Merge Method (PropertyMetadata, DependencyProperty)


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Merges this metadata with the base metadata.

Namespace:   System.Windows
Assembly:  WindowsBase (in WindowsBase.dll)

protected virtual void Merge(
	PropertyMetadata baseMetadata,
	DependencyProperty dp


Type: System.Windows.PropertyMetadata

The base metadata to merge with this instance's values.

Type: System.Windows.DependencyProperty

The dependency property to which this metadata is being applied.

This method is used internally when metadata is being overridden (OverrideMetadata method).

Notes to Inheritors:

Class implementations that derive from PropertyMetadata should override this method to account for any metadata properties they have added in their implementations. For instance, your implementation might have added a new flagwise enumeration value, and the Merge implementation should then be able to combine those flags correctly.

Always call the base implementation prior to your implementation code, because the base implementation takes care of merging all the properties already defined on the PropertyMetadata type.

The exact behavior of the merge is up to you. You could choose to have values combined, revert to base value if the derived metadata were left at the default, or many other behaviors based on the types of properties you have added to your particular metadata class, and their meanings.

The following example implements a merge for a custom metadata type that adds an additional property to the property metadata.

public Boolean SupportsMyFeature
    get { return _supportsMyFeature; }
    set { if (this.IsSealed != true) _supportsMyFeature = value; } //else may want to raise exception 
protected override void Merge(PropertyMetadata baseMetadata, DependencyProperty dp)
    base.Merge(baseMetadata, dp);
    MyCustomPropertyMetadata mcpm = baseMetadata as MyCustomPropertyMetadata;
    if (mcpm != null)
        if (this.SupportsMyFeature == false)
        {//if not set, revert to base
            this.SupportsMyFeature = mcpm.SupportsMyFeature;

.NET Framework
Available since 3.0
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