可编辑的ComboBox

Question

我想创建具有以下属性的可编辑组合框:

1. 将text属性绑定到我的数据模型.
2. 即使在选择已更改,数据模型也可能会覆盖GUI中的更改.例如,我可以选择1,2,3我选择2,但是一些组件下调将其更改为3.

3. 更新以下事件的数据模型:

   1. 选择改变了
   2. 失去焦点
   3. 输入按下(应该与失去的焦点相同).

我已经能够创建这样的控件,但它非常难看(使用很多hacks),我希望有一种更简单的方法......

提前致谢

Answer 1

好吧，这就是我所做的，而且它并没有那么难看：

 /// <summary>
/// Editable combo box which updates the data model on the following:
/// 1. Select## Heading ##ion changed
/// 2. Lost focus
/// 3. Enter or Return pressed
/// 
/// In order for this to work, the EditableComboBox requires the follows, when binding:
/// The data model value should be bounded to the Text property of the ComboBox
/// The binding expression UpdateSourceTrigger property should be set to LostFocus
/// e.g. in XAML:
/// <PmsEditableComboBox Text="{Binding Path=MyValue, UpdateSourceTrigger=LostFocus}"
/// ItemsSource="{Binding Path=MyMenu}"/>
/// </summary>
public class PmsEditableComboBox : ComboBox
{
    /// <summary>
    /// Initializes a new instance of the <see cref="PmsEditableComboBox"/> class.
    /// </summary>
    public PmsEditableComboBox()
        : base()
    {
        // When TextSearch enabled we'll get some unwanted behaviour when typing
        // (i.e. the content is taken from the DropDown instead from the text)
        IsTextSearchEnabled = false;
        IsEditable = true;
    }

    /// <summary>
    /// Use KeyUp and not KeyDown because when the DropDown is opened and Enter is pressed
    /// We'll get only KeyUp event
    /// </summary>
    protected override void OnKeyUp(KeyEventArgs e)
    {
        base.OnKeyUp(e);

        // Update binding source on Enter
        if (e.Key == Key.Return || e.Key == Key.Enter)
        {
            UpdateDataSource();
        }
    }

    /// <summary>
    /// The Text property binding will be updated when selection changes
    /// </summary>
    protected override void OnSelectionChanged(SelectionChangedEventArgs e)
    {
        base.OnSelectionChanged(e);
        UpdateDataSource();
    }

    /// <summary>
    /// Updates the data source.
    /// </summary>
    private void UpdateDataSource()
    {
        BindingExpression expression = GetBindingExpression(ComboBox.TextProperty);
        if (expression != null)
        {
            expression.UpdateSource();
        }
    }

}