Last and first day of the week

In a project I had to find out if a specific date was the first or last day of the week. Also, here in Norway we have Monday as the first day of the week, but in USA they use Sunday. I wanted my code to support this as well.

LINQPad

I discovered this tool a long time ago, but did not find it that useful, since I already is able to write LINQ to SQL queries in Visual Studio. Even in the Express Editions of Visual Studio I am able to write them with intellisense, something you have to pay for when using LINQPad. But recently a colleague showed me some more features that made me buy it.