The HyperLink control gets its Text from the Review instance that it’s bound to and uses its Id to build up the NavigateUrl. The ToString method is used on Item.Id to convert the value to a string before it’s concatenated to the string that contains the URL. This is done to avoid type conversions in Visual Basic where Item.Id normally results in a number that you can’t concatenate to a string directly. As an alternative, if you’re following along in VB.NET, you could have used the & character to concatenate the value.
To see how these controls get their data, you need to look at the Code Behind that uses a LINQ query targeting the Entity Framework: