Why would var be a bad thing?

Question

I\'ve been chatting with my colleagues the other day and heard that their coding standard explicitly forbids them to use the var keyword in C#. They had no idea

Answer 1

You may consider Microsoft's opinion to be relevant, since C# is their language:

"However, the use of var does have at least the potential to make your code more difficult to understand for other developers. For that reason, the C# documentation generally uses var only when it is required."

See MSDN - Implicitly Typed Local Variables (C# Programming Guide), last paragraph.

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You should also be aware that var removes the compile-time datatype test on the initial assignment.

var x = "mistake";     // error not found by compiler
int x = "mistake";     // error found

Since most variables are only assigned once, consistent use of var removes almost all datatype tests on variable assignments.

This makes your code vulnerable to accidental changes e.g. those made by merge tools or tired developers.