我正在尝试制作ListViewExtensions类，但出现一些错误

Question

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

namespace MinimizeCapture
{
    public partial class ListViewCostumControl : UserControl
    {
        public static ListViewControl lvnf;

        public ListViewCostumControl()
        {
            InitializeComponent();

            lvnf = new ListViewControl();
            lvnf.Location = new Point(50, 50);
            lvnf.Size = new Size(50, 50);
            lvnf.View = View.SmallIcon;
            lvnf.Dock = DockStyle.Fill;
            lvnf.SuspendLayout();
            lvnf.LabelEdit = true;
            lvnf.Sorting = SortOrder.None;
            this.Controls.Add(lvnf);
            lvnf.ResumeLayout(false);
        }

        public class ListViewControl : System.Windows.Forms.ListView
        {
            public ListViewControl()
            {
                this.SetStyle(ControlStyles.OptimizedDoubleBuffer | ControlStyles.AllPaintingInWmPaint, true);
                this.SetStyle(ControlStyles.EnableNotifyMessage, true);
            }

            protected override void OnNotifyMessage(System.Windows.Forms.Message m)
            {
                if (m.Msg != 0x14)
                {
                    base.OnNotifyMessage(m);
                }
            }
        }

        public static class ListViewExtensions
        {
            public static ListViewItemCollection AddRange(this ListViewItemCollection source, WindowSnapCollection windows)
            {
                //Create a ListViewItem for each object and set the 
                //various properties appropriately
                source.AddRange(from w in windows
                                select new ListViewItem(w.ToString())
                                {
                                    Tag = w
                                });

                return source;
            }

            public static WindowSnap GetWindowSnap(this ListViewItem source)
            {
                return source.Tag as WindowSnap;
            }

            public static WindowSnap GetSelectedWindowSnap(this ListView source)
   {
       return source.SelectedItem?.GetWindowSnap();
   }

            //Add more methods as needed
        }

        private void ListViewNFTest_Load(object sender, EventArgs e)
        {

        }
    }
}

The errors are on the lines

public static ListViewItemCollection AddRange(this ListViewItemCollection source, WindowSnapCollection windows)

Error 16 The type or namespace name 'ListViewItemCollection' could not be found (are you missing a using directive or an assembly reference?)

return source.SelectedItem?.GetWindowSnap();

Error 18 'System.Windows.Forms.ListView' does not contain a definition for 'SelectedItem' and no extension method 'SelectedItem' accepting a first argument of type 'System.Windows.Forms.ListView' could be found (are you missing a using directive or an assembly reference?)

Error 19 No overload for method 'GetWindowSnap' takes 0 arguments

Answer 1

It looks like you need to fully qualify some class names.

The class ListViewItemCollection is defined in ListView. So you need to fully qualify it with ListView.ListViewItemCollection.

public static ListView.ListViewItemCollection AddRange(
    this ListView.ListViewItemCollection source, 
    WindowSnapCollection windows)

WindowSnap and WindowSnap collection are not part of .NET, and you don't provide the definition so it's not clear how to use them. Figure out where they are defined and use the full class name, including namespace. Replace all occurrences of WindowSnap with Namespace.WindowSnap , and same goes for WindowSnapCollection.

See this MSDN article on fully qualified names for more info.