Over a decade ago, a small team of designers met in a small conference room on the second floor of Building 41 at Microsoft to create a brand-new language, C#. The guiding principles of the language emphasized simplicity, familiarity, safety, and practicality. Of course, all those principles needed to balance against one another; none are absolutes. The designers wanted the language to be simple to understand but not simplistic, familiar to C++ and Java programmers but not a slavish copy of either, safe by default but not too restrictive, and practical but never abandoning a disciplined, consistent, and theoretically valid design. After many, many months of thought, design, development, testing, and documentation, C# 1.0 was delivered to the public. It was a pretty straightforward object-oriented language. Many aspects of its design were carefully chosen to ensure that objects could be organized into independently versionable components, but the fundamental concepts of the language came from ideas developed in object-oriented and procedural languages going back to the 1970s or earlier.

The design team continued to meet three times a week in that same second-floor conference room to build upon the solid base established by C# 1.0. By working with colleagues in Microsoft Research Cambridge and the CLR team across the street, the type system was extended to support parametric polymorphism on generic types and methods. They also added “iterator blocks” (sometimes known as “generators” in other languages) to make it easier to build iterable collections and anonymous methods. Generics and generators had been pioneered by earlier languages such as CLU and Ada in the 1970s and 1980s; the idea of embedding anonymous methods in an existing method goes all the way back to the foundations of modern computer science in the 1950s.

C# 2.0 was a huge step up from its predecessor, but still the design team was not content. They continued to meet in that same second-floor conference room three times a week. This time, they were thinking about fundamentals. Traditional “procedural” programming languages do a good job of basic arithmetic, but the problems faced by modern developers go beyond adding a column of numbers to find the average. They realized that programmers manipulate data by combining relatively simple operations in complex ways. Operations typically include sorting, filtering, grouping, joining, and projecting collections of data. The concept of a syntactic pattern for “query comprehensions” that concisely describes these operations was originally developed in functional languages such as Haskell but also works well in a more imperative language like C#. And thus LINQ—Language Integrated Query— was born.