聚焦时更改绑定对象不会更新 TextBox

Question

如果我更改当前焦点 TextBox 的数据绑定对象，则 TextBox 不会显示新值。

给定一个带有按钮、标签和文本框的简单表单，使用下面的代码。如果用户更改了文本框的值和制表符，文本不会被重置以匹配新绑定的值（本例中为 20）。但是，如果我通过按钮单击事件触发更新，则文本框更新正常。

当属性更改事件在此处触发时，如何获取文本框值以显示新绑定的值 (20)？

using System;
using System.ComponentModel;
using System.Windows.Forms;

namespace BindingsUpdate
{
    public partial class Form1 : Form
    {
        private MyData _data;
        private System.Windows.Forms.BindingSource myDataBindingSource;   
        public Form1()
        {
            InitializeComponent();
            this.components = new System.ComponentModel.Container();
            this.myDataBindingSource = new System.Windows.Forms.BindingSource(this.components);
            this.myDataBindingSource.DataSource = typeof(BindingsUpdate.MyData);
            this.textBox1.DataBindings.Add(new System.Windows.Forms.Binding("Text", this.myDataBindingSource, "Value", true));
            this.label1.DataBindings.Add(new System.Windows.Forms.Binding("Text", this.myDataBindingSource, "Value", true));

            _data = new MyData () { Value = 10.0};

            this.myDataBindingSource.DataSource = _data;

            _data.PropertyChanged += Data_PropertyChanged;
        }

        private void Data_PropertyChanged (object sender, PropertyChangedEventArgs e)
        {
            RefreshData ();
        }

        private void RefreshData ()
        {
            _data.PropertyChanged -= Data_PropertyChanged;
            _data = new MyData () {Value = 20.0};
            this.myDataBindingSource.DataSource = _data;

            //these don't seem to do anything..
            this.myDataBindingSource.ResetBindings(false);
            this.myDataBindingSource.ResetCurrentItem();

            _data.PropertyChanged += Data_PropertyChanged;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            RefreshData ();
        }
    }

    public class MyData : INotifyPropertyChanged
    {
        private double _value;

        public double Value
        {
            get { return _value; }
            set
            {
                if (value.Equals(_value)) return;
                _value = value;
                OnPropertyChanged("Value");
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

Answer 1

您的 DataBindings 已过时，因为您替换了现有的 DataSource。

尝试清除并重新添加它们：

this.textBox1.DataBindings.Clear();
this.textBox1.DataBindings.Add(new Binding("Text", this.myDataBindingSource, "Value", true));