c＃绑定前更改属性值

我不确定此问题是否曾经被问过，但我目前处于将我的控件属性绑定到DependencyProperty但是， Property返回的值是Double类型。 设置绑定时，如何从属性中减去20或给定值，然后绑定控件？ 我需要为此实现IValueConverter吗？ 我还在学习WPF所以任何帮助将不胜感激。

依赖属性

 public static readonly DependencyProperty ProgressbarValueDependency = DependencyProperty.Register("PrValue", typeof(double), typeof(LinearProgressBar)); public double PrValue { get { return System.Convert.ToDouble(GetValue(ProgressbarValueDependency)); } set { SetValue(ProgressbarValueDependency, value); } } 

绑定到酒店

  { MainGrid = GetTemplateChild("MainGrid"); Binding MainGridWidthBinding = new Binding("PrValue") { Source = this, Mode = BindingMode.TwoWay }; MainGrid.SetBinding(Grid.WidthProperty, MainGridWidthBinding); } 

Answer 1

为了达到你的目的，你需要编写一个类实现IValueConverter接口。

 public class MyConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, string language) { // Contain your source to target convertion logic. } public object ConvertBack(object value, Type targetType, object parameter, string language) { // Contain your target to source convertion logic. // Only needed if using TwoWay or OneWayToSource Binding Mode. } } 

然后在调用SetBinding方法之前将其实例设置为Binding.Converter属性。

 Binding MainGridWidthBinding = new Binding("PrValue") { Source = this, Mode = BindingMode.TwoWay, Converter = new MyConverter(), }; MainGrid.SetBinding(Grid.WidthProperty, MainGridWidthBinding); 

Answer 2

最好的方法是实现一个IValueConverter，这是一个例子。

 using System; using System.Windows.Data; namespace WpfApp1 { public class DoubleModifierConverter : IValueConverter { public double Modifier { get; set; } public Operator Operator { get; set; } = Operator.Addition; public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { if (!(value is double doubleValue)) throw new InvalidCastException(); switch (Operator) { case Operator.Addition: return doubleValue + Modifier; case Operator.Substraction: return doubleValue - Modifier; case Operator.Multiplication: return doubleValue * Modifier; case Operator.Division: return doubleValue / Modifier; default: throw new ArgumentOutOfRangeException(); } } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { if (!(value is double doubleValue)) throw new InvalidCastException(); switch (Operator) { case Operator.Addition: return doubleValue - Modifier; case Operator.Substraction: return doubleValue + Modifier; case Operator.Multiplication: return doubleValue / Modifier; case Operator.Division: return doubleValue * Modifier; default: throw new ArgumentOutOfRangeException(); } } } public enum Operator { Addition = 0, Substraction = 1, Multiplication = 2, Division = 3, } } 

这就是你如何使用它。

 MainGrid = GetTemplateChild("MainGrid"); Binding MainGridWidthBinding = new Binding(nameof(PrValue)){ Source = this, Mode = BindingMode.TwoWay, Converter = new DoubleModifierConverter { Modifier = 20.0, Operator = Operator.Substraction } }; MainGrid.SetBinding(Grid.WidthProperty, MainGridWidthBinding);