c＃如何将selectedItems（listview）复制到变量中，然后在ListView中使用它（复制和粘贴）FileExplorer

Question

im making a file explorer tool in c# .. im using ListView to explore files

but i have an issue when i copy items(files)

public ListView.SelectedListViewItemCollection copiedItems;

private void btnCopy_Click(object sender, EventArgs e)
    {
        copiedItems = listView1.SelectedItems;
        infoLabel.Text = "Item(s) copied to clipboard.";
    }

private void Paste()
    {
        if (copiedItems != null)
        {
            foreach (ListViewItem item in copiedItems)
            {
                if (File.Exists(item.ToolTipText))
                {
                    if (MessageBox.Show(item.ToolTipText + "is already exists\r\nDo you want to overwrite it?"
                    , "Overwrite", MessageBoxButtons.OKCancel, MessageBoxIcon.Asterisk) == DialogResult.OK)
                    {
                        File.Copy(item.ToolTipText, currAddress, true);
                        infoLabel.Text = "Item(s) Pasted.";
                    }
                    return;
                }
                File.Copy(item.ToolTipText, currAddress, false);
                infoLabel.Text = "Item(s) Pasted.";
            }
        }
    }

when i change the folder that i am into(currAddress) .. the paste doesn't work because the

 ListView.SelectedListViewItemCollection copiedItems 

changed to null. .. here's my explorer code

private void DirRecursive(string path)
    {
            DirectoryInfo dir = new DirectoryInfo(path);
            currAddress = path;
            txtAddress.Text = path;
            _iconListManager.ClearLists();
            listView1.Items.Clear();
            foreach (DirectoryInfo folder in dir.GetDirectories())
                {
                    if ((folder.Attributes & FileAttributes.Hidden) == FileAttributes.Hidden)
                        continue;
                    ListViewItem item = new ListViewItem();
                    item.Text = folder.Name;
                    item.Tag = (object)folder.Parent;
                    item.ToolTipText = folder.FullName;
                    item.ImageIndex = _iconListManager.AddFolderIcon(folder.FullName);
                    listView1.Items.Add(item);
                }
                foreach (FileInfo file in dir.GetFiles())
                {
                    if ((file.Attributes & FileAttributes.Hidden) == FileAttributes.Hidden)
                        continue;
                    ListViewItem item = new ListViewItem();
                    item.Text = file.Name;
                    item.Tag = (object)file.Directory.Parent;
                    item.ToolTipText = file.FullName;
                    item.ImageIndex = _iconListManager.AddFileIcon(file.FullName);
                    item.SubItems.Add(CnvrtUnit(file.Length));
                    listView1.Items.Add(item);
                }

is there any explanation why copiedItems changed to null and how can i fix it ?

thanks in advance :)

Answer 1

I believe "listview1.SelectedItems" is just giving you a reference to the selected items. This means that "copiedItems" points to the same object as "listview1.SelectedItems". This is why when you clear the listview1 items in DirRecursive you clear the copiedItems. You need to get a separate copy of the items. To do this you should probably use something like this:

List<ListViewItem> copiedItems = new List<ListViewItem>();

foreach (ListViewItem item in listView1.Items)
{
    copiedItems.Add((ListViewItem) item.Clone());
}

Answer 2

Instead of

public ListView.SelectedListViewItemCollection copiedItems;

use

public List<string> copiedItems;

Change btnCopy_Click to this:

private void btnCopy_Click(object sender, EventArgs e)
    {
        copiedItems = listView1..SelectedItems.Cast<ListViewItem>().Select(li => li.ToolTipText).ToList();
        infoLabel.Text = "Item(s) copied to clipboard.";
    }

change Paste to this:

private void Paste()
    {
        if (copiedItems != null)
        {
            foreach (string item in copiedItems)
            {
                if (File.Exists(item))
                {
                    if (MessageBox.Show(item + "is already exists\r\nDo you want to overwrite it?"
                    , "Overwrite", MessageBoxButtons.OKCancel, MessageBoxIcon.Asterisk) == DialogResult.OK)
                    {
                        File.Copy(item, currAddress, true);
                        infoLabel.Text = "Item(s) Pasted.";
                    }
                    return;
                }
                File.Copy(item, currAddress, false);
                infoLabel.Text = "Item(s) Pasted.";
            }
        }
    }

Answer 3

The variable copiedItems isn't actually storing items, but rather storing a reference to where the selected items are. Or something to that effect. If the same items are selected at the time of the paste, you will be ok. But once the items are deselected in your list view, your copiedItems variable will now be an empty list. You need to explicitly copy the items that are selected when the copy button is pressed. The following sample program illustrates what I'm talking about. To make this run, create a new WinForms project, drag a ListView and two Button controls onto the form and replace the code in Form1.cs with the following.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        ListView.SelectedListViewItemCollection items1;
        List<int> items2;

        public Form1()
        {
            InitializeComponent();
            items2 = new List<int>();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            for (int i = 0; i < 10; i++)
            {
                listView1.Items.Add(i.ToString());
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            items1 = listView1.SelectedItems;
            foreach (var item in listView1.SelectedItems)
            {
                ListViewItem lvItem =(ListViewItem)item; 
                items2.Add(int.Parse(lvItem.Text));
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {

        }
    }
}