Question

我有很久以前从某个地方抓过的这个自定义控件：

public class NotifyingCollectionEditor : CollectionEditor
{
    // Define a static event to expose the inner PropertyGrid's PropertyValueChanged event args...
    public delegate void MyPropertyValueChangedEventHandler(object sender, PropertyValueChangedEventArgs e);
    public static event MyPropertyValueChangedEventHandler ElementChanged;

    // Inherit the default constructor from the standard Collection Editor...
    public NotifyingCollectionEditor(Type type) : base(type) { }

    // Override this method in order to access the containing user controls from the default Collection Editor form or to add new ones...
    protected override CollectionForm CreateCollectionForm()
    {
        // Getting the default layout of the Collection Editor...
        CollectionForm collectionForm = base.CreateCollectionForm();
        Form frmCollectionEditorForm = collectionForm as Form;
        TableLayoutPanel tlpLayout = frmCollectionEditorForm.Controls[0] as TableLayoutPanel;

        if (tlpLayout != null)
        {
            // Get a reference to the inner PropertyGrid and hook an event handler to it.
            if (tlpLayout.Controls[5] is PropertyGrid)
            {
                PropertyGrid propertyGrid = tlpLayout.Controls[5] as PropertyGrid;
                propertyGrid.PropertyValueChanged += new PropertyValueChangedEventHandler(propertyGrid_PropertyValueChanged);
            }
        }

        return collectionForm;
    }

    void propertyGrid_PropertyValueChanged(object sender, PropertyValueChangedEventArgs e)
    {
        // Fire our customized collection event...
        var evt = NotifyingCollectionEditor.ElementChanged;

        if (evt != null)
            evt(this, e);
    }
}

用于在集合中已编辑的项目之一发生更改时触发事件，但即使在此集合中添加或删除了某些项目，我也需要触发事件。

就目前而言，除了在创建表单时及其结束时比较元素数量时，我没有其他想法。

但是我如何才能访问该已修改的集合以获得Count值？

我尝试访问propertyGrid.SelectedObject但它是空的，即使它不是，我认为有收集项，而不是收集。

Answer 1

最好的办法是使用System.Collections.ObjectModel中定义的ObservableCollection。这将在添加或删除集合时引发事件。这个类是框架的一部分，所以现在和将来应该都能很好地工作。

如果您希望监控集合中的类型（T），那么该类型必须实现INotifyPropertyChanged。

Answer 2

public class NotifyingCollectionEditor : CollectionEditor
{
    // Define a static event to expose the inner PropertyGrid's PropertyValueChanged event args...
    public static event EventHandler<PropertyValueChangedEventArgs> ElementChanged;

    // Inherit the default constructor from the standard Collection Editor...
    public NotifyingCollectionEditor(Type type) : base(type) { }

    // Override this method in order to access the containing user controls from the default Collection Editor form or to add new ones...
    protected override CollectionForm CreateCollectionForm()
    {
        // Getting the default layout of the Collection Editor...
        CollectionForm collectionForm = base.CreateCollectionForm();
        Form frmCollectionEditorForm = collectionForm as Form;
        TableLayoutPanel tlpLayout = frmCollectionEditorForm.Controls[0] as TableLayoutPanel;

        if (tlpLayout != null)
        {
            // Get a reference to the inner PropertyGrid and hook an event handler to it.
            if (tlpLayout.Controls[5] is PropertyGrid)
            {
                PropertyGrid propertyGrid = tlpLayout.Controls[5] as PropertyGrid;
                propertyGrid.PropertyValueChanged += new PropertyValueChangedEventHandler(propertyGrid_PropertyValueChanged);
            }
        }

        return collectionForm;
    }

    protected override object SetItems(object editValue, object[] value)
    {
        object ret_val = base.SetItems(editValue, value);

        // Fire our customized collection event...
        var evt = NotifyingCollectionEditor.ElementChanged;

        if (evt != null)
            evt(this, null);

        return ret_val;
    }

    void propertyGrid_PropertyValueChanged(object sender, PropertyValueChangedEventArgs e)
    {
        // Fire our customized collection event...
        var evt = NotifyingCollectionEditor.ElementChanged;

        if (evt != null)
            evt(this, e);
    }
}

可以做到这一点。

如何在添加或删除项目时使CollectionEditor触发CollectionChanged事件？

2 个答案: