TabPage深度克隆异常：事件处理器与ComboBox项未被复制

我有一个包含多个面板及ComboBox、MaskedTextBox、TextBox、Button、DataGridView等嵌套控件的TabPage。我的目标是将该TabPage及其所有控件、对应事件处理器（如comboBox_SelectedIndexChanged、textBox_TextChanged、button_Click等）克隆为新的TabPage。

我编写了TabPageCloner类：

using System;
using System.Windows.Forms;
using System.Reflection;

public class TabPageCloner
{
    public static TabPage CloneTabPage(TabPage originalTab)
    {
        // Create a new TabPage instance
        TabPage newTab = new TabPage(originalTab.Text);

        // Clone each control on the original tab
        foreach (Control control in originalTab.Controls)
        {
            Control clonedControl = CloneControl(control);
            newTab.Controls.Add(clonedControl);
        }

        return newTab;
    }

    private static Control CloneControl(Control originalControl)
    {
        // Create an instance of the original control's type
        Control newControl = (Control)Activator.CreateInstance(originalControl.GetType());

        // Copy basic properties
        newControl.Text = originalControl.Text;
        newControl.Size = originalControl.Size;
        newControl.Location = originalControl.Location;
        newControl.Anchor = originalControl.Anchor;
        newControl.Dock = originalControl.Dock;

        // Clone any nested controls (for containers like Panels, GroupBoxes, etc.)
        if (originalControl.HasChildren)
        {
            foreach (Control childControl in originalControl.Controls)
            {
                Control clonedChild = CloneControl(childControl);
                newControl.Controls.Add(clonedChild);
            }
        }

        // Clone event handlers
        CloneEvents(originalControl, newControl);

        return newControl;
    }

    private static void CloneEvents(Control originalControl, Control newControl)
    {
        // Use reflection to clone event handlers
        EventInfo clickEvent = originalControl.GetType().GetEvent("Click");
        if (clickEvent != null)
        {
            FieldInfo eventField = typeof(Control).GetField("EventClick", BindingFlags.Static | BindingFlags.NonPublic);
            object eventDelegate = eventField?.GetValue(originalControl);

            if (eventDelegate is EventHandler eventHandlers)
            {
                foreach (Delegate handler in eventHandlers.GetInvocationList())
                {
                    clickEvent.AddEventHandler(newControl, handler);
                }
            }
        }

    }
}

在主窗体中使用方式：

TabPage clonedTabPage = TabPageCloner.CloneTabPage(MyOriginalTabPage);
tabControl1.TabPages.Add(clonedTabPage);
tabControl1.SelectedTab = clonedTabPage;

目前遇到两个问题：

1. 事件处理器完全未被克隆
2. ComboBox的项未被复制

1. ComboBox项未复制的问题 #

现有CloneControl仅复制了控件通用属性，未处理ComboBox这类控件的特有数据属性。需要针对特定控件类型，补充其专属属性/数据的克隆逻辑：

修改CloneControl方法，添加控件类型判断与专属处理：

private static Control CloneControl(Control originalControl)
{
    Control newControl = (Control)Activator.CreateInstance(originalControl.GetType());

    // 复制通用基础属性
    newControl.Text = originalControl.Text;
    newControl.Size = originalControl.Size;
    newControl.Location = originalControl.Location;
    newControl.Anchor = originalControl.Anchor;
    newControl.Dock = originalControl.Dock;
    newControl.Enabled = originalControl.Enabled;
    newControl.Visible = originalControl.Visible;

    // 克隆ComboBox的项与选中状态
    if (originalControl is ComboBox originalCombo)
    {
        ComboBox newCombo = (ComboBox)newControl;
        // 处理数据源绑定场景
        newCombo.DataSource = originalCombo.DataSource;
        newCombo.DisplayMember = originalCombo.DisplayMember;
        newCombo.ValueMember = originalCombo.ValueMember;
        // 处理手动添加项的场景
        foreach (var item in originalCombo.Items)
        {
            newCombo.Items.Add(item);
        }
        newCombo.SelectedIndex = originalCombo.SelectedIndex;
    }

    // 扩展：克隆MaskedTextBox的掩码与文本
    if (originalControl is MaskedTextBox originalMasked)
    {
        MaskedTextBox newMasked = (MaskedTextBox)newControl;
        newMasked.Mask = originalMasked.Mask;
        newMasked.Text = originalMasked.Text;
    }

    // 递归克隆子控件
    if (originalControl.HasChildren)
    {
        foreach (Control childControl in originalControl.Controls)
        {
            Control clonedChild = CloneControl(childControl);
            newControl.Controls.Add(clonedChild);
        }
    }

    CloneEvents(originalControl, newControl);
    return newControl;
}

2. 事件处理器未克隆的问题 #

现有CloneEvents仅处理了Click事件，且获取委托的逻辑错误——EventClick是Control类的静态事件键，并非实例的委托列表。正确做法是通过控件的Events属性遍历所有已注册事件：

修改CloneEvents方法为通用事件克隆逻辑：

private static void CloneEvents(Control originalControl, Control newControl)
{
    // 获取控件非公开的Events属性
    PropertyInfo eventsProperty = typeof(Control).GetProperty("Events", BindingFlags.Instance | BindingFlags.NonPublic);
    if (eventsProperty == null) return;

    EventHandlerList originalEvents = (EventHandlerList)eventsProperty.GetValue(originalControl);
    EventHandlerList newEvents = (EventHandlerList)eventsProperty.GetValue(newControl);

    // 遍历所有静态事件字段（包括子类自定义事件）
    FieldInfo[] eventFields = originalControl.GetType().GetFields(BindingFlags.Static | BindingFlags.NonPublic);
    foreach (FieldInfo field in eventFields)
    {
        if (field.FieldType == typeof(EventHandlerList.Key))
        {
            object eventKey = field.GetValue(null);
            Delegate originalDelegate = originalEvents[eventKey];
            if (originalDelegate != null)
            {
                // 复制所有委托调用列表
                foreach (Delegate handler in originalDelegate.GetInvocationList())
                {
                    newEvents.AddHandler(eventKey, handler);
                }
            }
        }
    }
}

补充说明 #

• 该反射方式依赖WinForms内部实现，当前版本稳定但后续框架更新可能存在兼容性风险；
• 如需克隆DataGridView，需额外补充列定义、行数据等专属逻辑，可参考ComboBox的类型判断方式扩展；
• 自定义控件的事件需确保事件字段为静态非公开，否则无法被捕获克隆。

内容的提问来源于stack exchange，提问作者Oldhuntersblood