c# - 控制不立即使用 INotifyPropertyChanged 更新绑定(bind)属性

Question

我的控件在失去焦点之前不会更新其绑定(bind)对象的相应属性。有类似的问题，接受的答案引用 DataSourceUpdateMode.OnPropertyChange 被声明，我这样做，但行为仍然存在。这是一个示例实现。我会尽量做到全面而简洁。 MyConfig 类是通过我称为 Configuration 的 Singleton 类中的属性访问的。

[Serializable]
public class MyConfig : INotifyPropertyChanged
{
    public enum MyEnum
    {
        Foo,
        Bar
    }

    public MyConfig()
    {
        MyProperty = MyEnum.Foo;
    }

    private MyEnum _MyProperty;
    public MyEnum MyProperty
    {
        get { return _MyProperty; }
        set { if (value != _MyProperty) { _MyProperty = value; OnPropertyChanged("MyProperty"); } }
    }

    [field: NonSerialized]
    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string propertyName)
    {
        if (string.IsNullOrEmpty(propertyName))
            throw new ArgumentNullException(propertyName);
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

public partial class ConfigForm : Form
{
    public ConfigForm()
    {
        InitializeComponent();
        MyComboBox.Items.AddRange(Enum.GetNames(typeof(MyConfig.MyEnum)));
    }

    private void ConfigForm_Load(object sender, EventArgs e)
    {
        MyComboBox.DataSource = Enum.GetValues(typeof(MyConfig.MyEnum));
        MyComboBox.DataBindings.Add("SelectedItem", Configuration.Instance.MyConfig, "MyProperty", false, DataSourceUpdateMode.OnPropertyChanged);
    }
}

鉴于以下简要实现，我不确定我可能会忽略哪些内容以确保立即更改属性。在本例中，我可以更改 ComboBox 中的 Foo 到 Bar，但除非我从 ComboBox 中移除焦点，否则什么都不会改变。有人有什么想法吗？

Answer 1

WinForms ComboBox 与 OnPropertyChanged 有关。下面是我用来使 OnPropertyChanged 以我期望的方式为 SelectedItem 属性工作的旧项目的一些代码。这适用于我的特定实例，但有时我通常很难让这种情况发挥作用。祝你好运!

/// <summary>
/// A modification of the standard <see cref="ComboBox"/> in which a data binding
/// on the SelectedItem property with the update mode set to DataSourceUpdateMode.OnPropertyChanged
/// actually updates when a selection is made in the combobox.
/// </summary>
public class BindableComboBox : ComboBox
{
    /// <summary>
    /// Raises the <see cref="E:System.Windows.Forms.ComboBox.SelectionChangeCommitted"/> event.
    /// </summary>
    /// <param name="e">An <see cref="T:System.EventArgs"/> that contains the event data.</param>
    protected override void OnSelectionChangeCommitted(EventArgs e)
    {
        base.OnSelectionChangeCommitted(e);

        var bindings = this.DataBindings
            .Cast<Binding>()
            .Where(x => 
                x.PropertyName == "SelectedItem" && 
                x.DataSourceUpdateMode == DataSourceUpdateMode.OnPropertyChanged);
        foreach (var binding in bindings)
        {
            // Force the binding to update from the new SelectedItem
            binding.WriteValue();

            // Force the Textbox to update from the binding
            binding.ReadValue();
        }
    }
}