更改綁定對象時不會更新文本框集中

Question

如果我更改當前集中文本框的數據綁定對象，文本框不會顯示新值。

給定一個帶有按鈕，標籤和文本框的簡單表單，請使用下面的代碼。如果用戶更改了文本框的值和製表符，則不會重置文本以匹配新綁定的值（本例中爲20）。但是，如果我通過按鈕單擊事件觸發更新，文本框更新正常。

當屬性更改事件在此處觸發時，如何獲取文本框的值以顯示新綁定的值（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

由於您替換了現有的DataSource，您的DataBindings已陳舊。

嘗試清除和添加他們回來：

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