Question

Is there a more efficient way to do this using LINQ or String.Join?

var sb = new StringBuilder();
foreach (var s in cls.Students)
  sb.Append("<div id=\"s" + s.Id + "\">" + s.FirstName +
            " " + s.LastName + "</div>");

Answer 1

You can use string.Concat:

string result = string.Concat(cls.Students.Select(
    s => string.Format("<div id=\"s{0}\">{1} {2}</div>", s.Id, s.FirstName, s.LastName)
));

It’s a little more concise, but it probably won’t give you more performance. Using a StringBuilder is already very efficient.

Notes

• In .NET 3.5 and older you will also need to add .ToArray() just before the last parenthesis.
• You should HTML escape s.FirstName and s.LastName. I’m assuming s.ID is an integer and therefore is safe.