C#绑定到嵌套对象上的字段
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09-10-2019 - |
题
我似乎找不到使用数据绑定在Winforms应用程序中绑定控件中的控件与嵌套对象的简单,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,第一个是姓名,第二个是innit.somebalue。我很容易就可以与名称作用,但是内在价值是片状的。如果我填充对象然后设置绑定,则在文本框中显示innear.somebebalue,但我无法编辑它。如果我从新鲜的对象开始而不初始化内部对象,那么我似乎无法将数据粘贴在inner.somebalue中。
我已经检查了整个MSDN,遍布Stackoverflow,并使用了数十个具有不同关键字的搜索。每个人都想谈论与数据库或数据杂志的绑定,并且大多数示例都是用XAML编写的。
更新:我尝试了MARC的完整测试安全带,并取得了部分成功。如果我打“全部变化!”按钮,我似乎能够回到内部对象。但是,从myObject.inner null开始,它不知道如何创建内部对象。我认为目前,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。不过,我不禁感到自己缺少一些东西:)
解决方案
嗯 - 一个很好的问题;我已经对对象做了很多数据结合,我将 发誓 你正在做的应该有效;但是确实,注意到内部对象的变化是非常不愿意的。我设法通过:
var outer = new BindingSource { DataSource = myObject };
var inner = new BindingSource(outer, "Inner");
txtName.DataBindings.Add("Text", outer, "Name");
txtSomeValue.DataBindings.Add("Text", inner, "SomeValue");
不是理想的,但它起作用。顺便提一句;您可能会发现以下实用程序方法有用:
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));
}
}
然后,您可以:
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;
}
在讨价还价中,它解决了无效的(种族条件)的(纤细)机会。
完整的测试钻机,以熨烫扭结(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);
}
}
}
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