To var or not to var: how do C# developers use and misuse implicit and explicit typing?

When implicit typing with the “var” keyword was introduced into C#, it prompted contradictory opinions among developers. This paper starts by explaining the difference between implicit and explicit typing and then provides an overview of developers’ opinions and guidelines that are available online. This paper then reports on the results of a study that investigated how C# developers use and misuse implicit and explicit typing. This study involved analyzing the source code of 10 different open-source software projects including more than 16,500,000 lines of code and more than 930,000 variables. This study investigated to what extent developers use a form of typing that affects the readability of a variable’s type and the length of its declaration. It also investigated whether or not there is an adoption of a consistent set of guidelines in general and across each software project. A tool called “Code Analysis and Refactoring Engine for C#” (Care#) was developed and used to conduct the code analysis for this study.