如何检查ToolStripMenuItem DropDownItems中是否已存在项目？

Question

items = File
    .ReadLines(RecentFiles)
    .Select(line => new ToolStripMenuItem()
    {
        Text = line
    })
    .ToArray();
recentFilesToolStripMenuItem.DropDownItems.AddRange(items);

I want to check if the items exist already in the recentFilesToolStripMenuItem.DropDownItems

If not exist add but if exist don't add.

Answer 1

You basically have two collections: items & recentFilesToolStripMenuItem.DropDownItems

Using Linq , you should be able to do an Except() a Where() to only add the difference between the two collections.

This is not tested.

recentFilesToolStripMenuItem.DropDownItems.AddRange(items.Except(recentFilesToolStripMenuItem.DropDownItems));

This is tested

recentFilesToolStrip.DropDownItems.AddRange(
    items
    .Where(i => !recentFilesToolStrip.DropDownItems
                 .OfType<ToolStripMenuItem>()
                 .Select(t => t.Text).Contains(i.Text)
          ).ToArray()
);

SLaks comment refers to doing something like the following:

recentFilesToolStripMenuItems.DropDownItems.Clear();
recentFilesToolStripMenuItems.DropDownItems.AddRange(items);