LINQ and LINQPad
- 2. What is LINQ? Language Integrated Query - part of Microsoft .NET Framework Formulate queries directly in C# and VB instead of SQL LINQ-to-objects (in-memory data) LINQ-to-entities (ORM <-> SQL)
- 3. Why LINQ? No need to learn a new query syntax, use your C# programming chops. Single, consistent query language for working with data - in memory or in databases. Widely used, adapters for most databases you can think of: MySQL, MariaDB, MSSQL, PostgreSQL, MongoDB, CouchDB, ...
- 4. LINQ - Two tales of syntax Query syntax - “SQL-like” Method syntax - “C#-like”
- 5. LINQ - Operations Select (map) SelectMany (flatten)
- 6. LINQ - Operations Where (filter) Aggregrate (reduce)
- 7. LINQ - Operations Ordering Join GroupBy Aggregates - Min, Max, Sum, Count, Average Set - Union, Distinct, Intersect, Except Element - First, FirstOrDefault, Last, LastOrDefault Qualifiers - Any, All, Contains Partitioning - Take, Skip Conversions - ToList, ToDictionary, ToArray, Cast<T>, OfType<T>
- 8. Extending LINQ-to-objects It is all about IEnumerable Nugets: MoreLINQ Writing your own Prepend() This won’t work against databases!
- 9. LINQ-to-entities (databases) Requires an ORM, Entity Framework ships with .NET for SQL Has adapters to all the popular databases, MSSQL, MySQL, MariaDB, PostgreSQL… LINQ is translated to SQL, so this doesn’t work But this does:
- 10. LINQ-to-entities (databases) LINQ is lazy, no query is run until you call .ToList().
- 11. LINQPad Awesome C# and LINQ scratchpad. Test out C#, F#, VisualBasic code-snippets Test out queries with LINQ, SQL, ESQL against databases Navigate the database from any result set, follow relations and dig deep into the data Intellisense and supports nugets Showtime!