Question

我需要TextBox来反映数据绑定字符串的变化。我尝试了以下代码：

public partial class Form1 : Form
{
    string m_sFirstName = "Brad";
    public string FirstName
    {
        get { return m_sFirstName; }
        set { m_sFirstName = value; }
    }

    public Form1()
    {
        InitializeComponent();

        textBox1.DataBindings.Add("Text", this, "FirstName");
    }

    private void buttonRename_Click(object sender, EventArgs e)
    {
        MessageBox.Show("before: " + FirstName);
        FirstName = "John";
        MessageBox.Show("after: " + FirstName);
    }
}

启动应用程序后，textBox1正确填充了Brad。我点击了按钮，它将FirstName重命名为“John”（第二个消息框确认了它）。但是textBox1仍然充满了布拉德，而不是约翰。为什么？什么使这项工作？

Answer 1

一种方法是添加一个FirstNameChanged事件，然后数据绑定将挂钩。然后在更改属性时引发事件，它将重新绑定。例如：

using System;
using System.Drawing;
using System.Windows.Forms;

public class DataBindingTest : Form
{
    public event EventHandler FirstNameChanged;

    string m_sFirstName = "Brad";
    public string FirstName
    {
        get { return m_sFirstName; }
        set 
        { 
            m_sFirstName = value;
            EventHandler handler = FirstNameChanged;
            if (handler != null)
            {
                handler(this, EventArgs.Empty);
            }
        }
    }

    public DataBindingTest()
    {
        Size = new Size(100, 100);
        TextBox textBox = new TextBox();
        textBox.DataBindings.Add("Text", this, "FirstName");

        Button button = new Button
        { 
            Text = "Rename",
            Location = new Point(10, 30)
        };
        button.Click += delegate { FirstName = "John"; };
        Controls.Add(textBox);
        Controls.Add(button);
    }

    static void Main()
    {
        Application.Run(new DataBindingTest());
    }
}

可能有其他方法（例如使用INotifyPropertyChanged） - 我不是任何方式的数据绑定专家。

Answer 2

DataBinding没有反映您的更改的原因是因为您绑定了一个简单的System.String对象，该对象尚未设计为在修改时抛出事件。

所以你有两个选择。一种是在按钮的Click事件中重新绑定值（请避免！）。另一种是创建一个将实现INotifyPropertyChanged的自定义类：

public partial class Form1 : Form
{
    public Person TheBoss { get; set; }

    public Form1()
    {
        InitializeComponent();

        TheBoss = new Person { FirstName = "John" };

        textBox1.DataBindings.Add("Text", this, "TheBoss.FirstName");
    }

    private void button1_Click(object sender, EventArgs e)
    {
        TheBoss.FirstName = "Mike";
    }


    public class Person : INotifyPropertyChanged
    {
        private string firstName;

        public string FirstName
        {
            get 
            { 
                return firstName; 
            }
            set 
            { 
                firstName = value;
                NotifyPropertyChanged("FirstName");
            }
        }

        private void NotifyPropertyChanged(String info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion
    }
}

INotifyPropertyChanged文档：MSDN

Answer 3

您需要在按钮单击时再次执行数据绑定，否则它只在表单实例化时运行一次。

要添加：上述声明不适合该要求。它仍然有效（参见下面的代码），但是通过事件处理来破坏绑定的目的。

Binding binding1; //binding instance
public Form1()
{
    InitializeComponent();
    binding1 = textBox1.DataBindings.Add("Text", this, "FirstName"); //assign binding instance
}

private void buttonRename_Click(object sender, EventArgs e)
{
    MessageBox.Show("before: " + FirstName);
    FirstName = "John";
    textBox1.DataBindings.Remove(binding1); //remove binding instance
    binding1 = textBox1.DataBindings.Add("Text", this, "FirstName"); //add new binding
    MessageBox.Show("after: " + FirstName);
}

数据绑定TextBox不反映源更改

3 个答案: