代码绑定问题

Question

 bindingWidth.Source = grid;
                    bindingWidth.Path = new Windows.UI.Xaml.PropertyPath("Width");
                    bindingWidth.Mode = BindingMode.OneWay;
上面的grid是一个Grid,我要把一个直线的y2绑定到grid宽的一半，怎样实现
lineLeft.X1 = 0;
                        lineLeft.Y1 = 0;
                        lineLeft.X2 = 0;
                        //lineLeft.Y2 = this.Height;
                        lineLeft.SetBinding(Line.Y2Property, bindingHeight);

Answer 1

Hi runqian,

我认为你需要一个Convert Class来帮助你转变长度，把下面这段代码放入到你的项目中。

    public class lineWidthConvert : IValueConverter
    {
        public object Convert(object value, Type targetType,
            object parameter, string language)
        {
            return (double)value / 2;
        }
        public object ConvertBack(object value, Type targetType,
            object parameter, string language)
        {
            throw new NotImplementedException();
        }
    }

在你的binding code中做如下修改，即可实现你想要的效果：

            Binding bindingWidth = new Binding();
            bindingWidth.Source = grid;
            bindingWidth.Path = new Windows.UI.Xaml.PropertyPath("Width");
            bindingWidth.Mode = BindingMode.OneWay;
            bindingWidth.Converter = new lineWidthConvert();

            lineLeft.X1 = 0;
            lineLeft.Y1 = 0;
            lineLeft.X2 = 0;
            //lineLeft.Y2 = this.Height;
            lineLeft.SetBinding(Line.Y2Property, bindingWidth);

--James

---

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Answer 2

thanks, It works

Answer 3

但是我现在有个问题，我想定义一个Bingding对象，想在多处使用，怎们会出错？

  Binding binding = new Binding();
                binding.Source = this.grid;
                binding.Path = new PropertyPath("Height");
                lineWidth.SetBinding(Line.Y2Property, binding);


                //Binding bindingHeight = new Binding();
                //binding.Source = this.grid;
                binding.Path = new PropertyPath("Width");
                //binding.Converter = new lineWidthConvert();


                //lineWidth.X2 = this.grid.Width;
                lineWidth.SetBinding(Line.X2Property, binding);

运行时会出COMException异常，不知道怎样解决？

Answer 4

Hi runqian,

Binding对象只处理一个，所以你需要新建一个Binding对象用于绑定Width。你可以试想如果同一个Binding应用到两个对象上去，如果一旦发生binding源发生变化，这两个对象如何处理binding？

所以你应该分开写这两个Binding。

--James

---

<THE CONTENT IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS OR IMPLIED>
Thanks
MSDN Community Support

Please remember to "Mark as Answer" the responses that resolved your issue. It is a common way to recognize those who have helped you, and makes it easier for other visitors to find the resolution later.