var query = DataContext().SomeTable.Where(u => u.UserID.contains("P");

var query = DataContext().SomeTable.Where(u => u.GetType().GetProperty("UserID").Name.contains("P");

((string)u.GetType().GetProperty("UserID").GetValue(u) ?? "").Contains("P")

u.GetType().GetProperty("UserID").GetValue(u, null).ToString().Contains("P");