Recently I ran into an issue with the contains method in LINQ in conjunction with the SingleOrDefault method.
My query was similar to:
var data = (from i in ctx.DataContext.orders
and this was throwing the error:
System.InvalidOperationException: Sequence contains more than one element
Turns out the Contains translated to a LIKE '%...%' and was returning multiple records. By changing this to i.Name == order, then I got back the single result I was expecting.