如何使 TextBox Left 更改将更新绑定类的 X 值？

Question

我有一个文本框，我改变了它的左值。并且此 TextBox 绑定到具有 X 属性的类。现在，当我更改 TextBox 的 Left 值时，我希望更新班级的 X。我应该怎么做才能强制更新我的数据绑定类属性？

Answer 1

由于数据绑定的工作原理，这种类型的 2-way 绑定仅在控件通告更改时才有效；通常通过*Changed 事件 - 在这种情况下即LeftChanged。由于没有这样的事件，你根本不能，除非继承 TextBox，重新声明 (new) Left 并添加一个与 LocationChanged 挂钩的 LeftChanged。

您可以向LocationChanged 添加一个事件并手动执行吗？还是在设置位置/左侧时手动更新对象？

---

using System;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    class SuperTextBox : TextBox
    {
        protected override void OnLocationChanged(EventArgs e)
        {
            base.OnLocationChanged(e);

            EventHandler handler = (EventHandler)Events[LeftChangedKey];
            if (handler != null) handler(this, EventArgs.Empty);
        }
        public event EventHandler LeftChanged
        {
            add { Events.AddHandler(LeftChangedKey, value); }
            remove { Events.RemoveHandler(LeftChangedKey, value); }
        }
        public new int Left
        {
            get { return base.Left; }
            set { base.Left = value; }
        }
        private static readonly object LeftChangedKey = new object();
    }
    class Person {
        private int value;
        public int Value {
            get {return value;}
            set {
                this.value = value;
                EventHandler handler = ValueChanged;
                if(handler!=null)
                {
                    handler(this, EventArgs.Empty);
                }
            }
        }
        public event EventHandler ValueChanged;
    }
    static class Program
    {
        static void Main()
        {
            Button btn;
            TextBox txt;
            Person p = new Person { Value = 10 };
            using (Form form = new Form {
                DataBindings = {{ "Text", p, "Value"}},
                Controls = {
                    (txt = new SuperTextBox {
                        DataBindings = {{ "Left", p, "Value", false,
                            DataSourceUpdateMode.OnPropertyChanged}}
                    }),
                    (btn = new Button {
                        Text = "bump",
                        Dock = DockStyle.Bottom
                    })
                }
            }) {
                btn.Click += delegate { txt.Left += 5; };
                Application.Run(form);
            }
        }
    }
}