/// <summary> /// Determines what value this converter should return. /// </summary> /// <param name="value">The value produced by the binding source.</param> /// <param name="targetType">The type of the binding target property.</param> /// <param name="parameter">The converter parameter to use.</param> /// <returns> /// <c>true</c> if the specified value is visible; otherwise, <c>false</c>. /// </returns> protected override bool IsVisible(object value, Type targetType, object parameter) { bool invert = ConverterHelper.ShouldInvert(parameter); return(invert ? (value == null) : (value != null)); }