我似乎找不到关于如何使用数据绑定(bind)将 WinForms 应用程序中的控件绑定(bind)到嵌套对象的简单、具体的解释。例如:
class MyObject : INotifyPropertyChanged
{
private string _Name;
public string Name
{
get { return _Name; }
set
{
_Name = value;
OnPropertyChanged("Name");
}
}
private MyInner _Inner;
public MyInner Inner
{
get { return _Inner; }
set
{
_Inner = value;
OnPropertyChanged("Inner");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
class MyInner : INotifyPropertyChanged
{
private string _SomeValue;
public string SomeValue
{
get { return _SomeValue; }
set
{
_SomeValue = value;
OnPropertyChanged("SomeValue");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
现在想象一个只有两个文本框的表单,第一个用于 Name,第二个用于 Inner.SomeValue。我可以很容易地绑定(bind)到 Name,但 Inner.SomeValue 是不稳定的。如果我填充对象然后设置绑定(bind),它会在文本框中显示 Inner.SomeValue 但我无法编辑它。如果我在没有初始化 Inner 的情况下从一个新对象开始,我似乎无法将数据粘贴到 Inner.SomeValue 中。
我已经检查了整个 MSDN、整个 StackOverflow 以及许多使用不同关键字的搜索。每个人都想谈论绑定(bind)到数据库或 DataGrid,大多数示例都是用 XAML 编写的。
更新:我尝试了 Marc 的完整测试工具并取得了部分成功。如果我点击“全部改变!”按钮,我似乎可以写回内部对象。但是,从 MyObject.Inner null 开始,它不知道如何创建内部对象。我想现在,我可以通过确保我的内部引用始终设置为有效对象来解决它。尽管如此,我还是忍不住觉得自己错过了什么:)
最佳答案
嗯 - 一个很好的问题;我对对象做了很多数据绑定(bind),我会发誓您所做的应该有效;但确实很不愿意注意到内部对象的变化。我设法让它工作:
var outer = new BindingSource { DataSource = myObject };
var inner = new BindingSource(outer, "Inner");
txtName.DataBindings.Add("Text", outer, "Name");
txtSomeValue.DataBindings.Add("Text", inner, "SomeValue");
不理想,但它有效。顺便提一句;您可能会发现以下实用方法很有用:
public static class EventUtils {
public static void SafeInvoke(this EventHandler handler, object sender) {
if(handler != null) handler(sender, EventArgs.Empty);
}
public static void SafeInvoke(this PropertyChangedEventHandler handler,
object sender, string propertyName) {
if(handler != null) handler(sender,
new PropertyChangedEventArgs(propertyName));
}
}
那么你可以:
class MyObject : INotifyPropertyChanged
{
private string _Name;
public string Name { get { return _Name; } set {
_Name = value; PropertyChanged.SafeInvoke(this,"Name"); } }
private MyInner _Inner;
public MyInner Inner { get { return _Inner; } set {
_Inner = value; PropertyChanged.SafeInvoke(this,"Inner"); } }
public event PropertyChangedEventHandler PropertyChanged;
}
class MyInner : INotifyPropertyChanged
{
private string _SomeValue;
public string SomeValue { get { return _SomeValue; } set {
_SomeValue = value; PropertyChanged.SafeInvoke(this, "SomeValue"); } }
public event PropertyChangedEventHandler PropertyChanged;
}
并且在讨价还价中它修复了空异常(竞争条件)的(微弱)机会。
完整的测试装置,以解决问题(来自评论):
using System;
using System.ComponentModel;
using System.Windows.Forms;
public static class EventUtils {
public static void SafeInvoke(this PropertyChangedEventHandler handler, object sender, string propertyName) {
if(handler != null) handler(sender, new PropertyChangedEventArgs(propertyName));
}
}
class MyObject : INotifyPropertyChanged
{
private string _Name;
public string Name { get { return _Name; } set { _Name = value; PropertyChanged.SafeInvoke(this,"Name"); } }
private MyInner _Inner;
public MyInner Inner { get { return _Inner; } set { _Inner = value; PropertyChanged.SafeInvoke(this,"Inner"); } }
public event PropertyChangedEventHandler PropertyChanged;
}
class MyInner : INotifyPropertyChanged
{
private string _SomeValue;
public string SomeValue { get { return _SomeValue; } set { _SomeValue = value; PropertyChanged.SafeInvoke(this, "SomeValue"); } }
public event PropertyChangedEventHandler PropertyChanged;
}
static class Program
{
[STAThread]
public static void Main() {
var myObject = new MyObject();
myObject.Name = "old name";
// optionally start with a default
//myObject.Inner = new MyInner();
//myObject.Inner.SomeValue = "old inner value";
Application.EnableVisualStyles();
using (Form form = new Form())
using (TextBox txtName = new TextBox())
using (TextBox txtSomeValue = new TextBox())
using (Button btnInit = new Button())
{
var outer = new BindingSource { DataSource = myObject };
var inner = new BindingSource(outer, "Inner");
txtName.DataBindings.Add("Text", outer, "Name");
txtSomeValue.DataBindings.Add("Text", inner, "SomeValue");
btnInit.Text = "all change!";
btnInit.Click += delegate
{
myObject.Name = "new name";
var newInner = new MyInner();
newInner.SomeValue = "new inner value";
myObject.Inner = newInner;
};
txtName.Dock = txtSomeValue.Dock = btnInit.Dock = DockStyle.Top;
form.Controls.AddRange(new Control[] { btnInit, txtSomeValue, txtName });
Application.Run(form);
}
}
}
关于c# 绑定(bind)到嵌套对象上的字段,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/3974627/