AJAX :: Can Use AutocompleteExtender In C#

In the tutorial for autocomplete text box for static page method in c# the following lines of code is given. When i use it my website using c# it gives error 'invalid term "in" showing in line 7.

[System.Web.Services.WebMethodAttribute(), System.Web.Script.Services.ScriptMethodAttribute()]
public static string[] GetCompletionList(string prefixText, int count, string contextKey) {
// Create array of movies string[] movies = {"Star Wars", "Star Trek", "Superman", "Memento", "Shrek", "Shrek II"};
// Return matching movies return (from m in movies where m.StartsWith(prefixText,StringComparison.CurrentCultureIgnoreCase) select m).Take(count).ToArray();
}