using System;

using System.Linq;

using System.Xml.Linq;

​

public class Program

{

    public static void Main()

    {

        const string xml = @"<root><span class=""screenItems""><content /><content /></span></root>";

        var doc = XDocument.Parse(xml);

        Console.WriteLine(doc);

        Console.WriteLine("--");

        var spans = doc.Descendants("span")

            .Where(e => (string)e.Attribute("class") == "screenItems")

            .ToList();

        foreach (var span in spans)

        {

            span.ReplaceWith(span.Nodes());

        }

        Console.WriteLine(doc);

    }

}