public ReadOnlyPropertyMetadata(object defaultValue, 
                                 GetReadOnlyValueCallback getValueCallback,
                                 PropertyChangedCallback propertyChangedCallback) :
                                 base(defaultValue, propertyChangedCallback)
 {
     _getValueCallback = getValueCallback;
 }
 public ReadOnlyPropertyMetadata(object defaultValue,
                                 GetReadOnlyValueCallback getValueCallback,
                                 PropertyChangedCallback propertyChangedCallback) :
     base(defaultValue, propertyChangedCallback)
 {
     _getValueCallback = getValueCallback;
 }
 public ReadOnlyFrameworkPropertyMetadata(object defaultValue, GetReadOnlyValueCallback getValueCallback) :
     base(defaultValue)
 {
     _getValueCallback = getValueCallback;
 }
 public ReadOnlyFrameworkPropertyMetadata(object defaultValue, GetReadOnlyValueCallback getValueCallback)
     : base(defaultValue)
 {
     this.getValueCallback = getValueCallback;
 }