C# WinForm拖拽ToolStripMenuItem至ListView并获取对象引用求助

Let's walk through how to resolve your issue step by step. The core problem here is twofold: you're incorrectly trying to cast the DragDrop event sender (which is always the ListView) to a ToolStripMenuItem, and the drag data wasn't being packaged properly to preserve the original menu item reference.

Step 1: Correct the Drag Data Packaging #

When starting the drag operation, explicitly package the ToolStripMenuItem into a DataObject to ensure it's carried through the drag-and-drop process. This avoids any implicit data handling that might lose the reference.

Update your mnulevel3_MouseDown event handler:

void mnulevel3_MouseDown(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Right)
    {
        ToolStripMenuItem menuItem = sender as ToolStripMenuItem;
        if (menuItem != null)
        {
            // Create a data object to hold our menu item reference
            DataObject dragData = new DataObject();
            dragData.SetData(typeof(ToolStripMenuItem), menuItem);
            
            // Start the drag operation
            menuItem.DoDragDrop(dragData, DragDropEffects.Copy);
        }
    }
}

Step 2: Validate Drag Data in DragEnter #

Only allow the drop if the incoming data contains a ToolStripMenuItem to avoid invalid operations:

private void listView1_DragEnter(object sender, DragEventArgs e)
{
    // Check if the drag data is our ToolStripMenuItem
    if (e.Data.GetDataPresent(typeof(ToolStripMenuItem)))
    {
        e.Effect = DragDropEffects.Copy;
    }
    else
    {
        e.Effect = DragDropEffects.None;
    }
}

Step 3: Retrieve Original Menu Item in DragDrop #

Pull the ToolStripMenuItem from the drag data, create your ListViewItem, and store the original menu item in the ListViewItem.Tag property so you can access it later:

private void listView1_DragDrop(object sender, DragEventArgs e)
{
    try
    {
        if (e.Data.GetDataPresent(typeof(ToolStripMenuItem)))
        {
            ToolStripMenuItem originalMenuItem = (ToolStripMenuItem)e.Data.GetData(typeof(ToolStripMenuItem));
            
            if (originalMenuItem != null)
            {
                ListViewItem lvItem = new ListViewItem(originalMenuItem.Text);
                // Store the original menu item reference for later access
                lvItem.Tag = originalMenuItem;
                listView1.Items.Add(lvItem);
            }
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show($"Error during drop: {ex.Message}");
    }
}

Step 4: Access Original Menu Item When Selecting ListViewItem #

To access the original ToolStripMenuItem properties when a ListViewItem is selected, use the Tag property:

private void listView1_SelectedIndexChanged(object sender, EventArgs e)
{
    if (listView1.SelectedItems.Count > 0)
    {
        ListViewItem selectedItem = listView1.SelectedItems[0];
        ToolStripMenuItem originalMenu = selectedItem.Tag as ToolStripMenuItem;
        
        if (originalMenu != null)
        {
            // Access any property from the original menu item
            MessageBox.Show($"Original Menu Text: {originalMenu.Text}\nTag Value: {originalMenu.Tag}");
        }
    }
}

Why Your Original Code Failed #

• You tried casting the DragDrop event sender (which is the ListView control) to ToolStripMenuItem—this will always throw a cast error.
• The drag data wasn't explicitly packaged, which could lead to the e.Data.GetData call returning null (especially with right-click drag operations, which have different default behavior than left-click).

Content of the question来源于stack exchange，提问作者Priya