How can I track a variable's values as they change, at runtime, in C#? I'm interested in the same functionality that the debugger provides when I'm tracing a variable through execution steps, only that I need to call upon it from my code. Some sort of key-value observing, but for all kinds of variables(local, class, static, etc), not only properties. So, basically, receive a notification when a variable's value changes.
You are working from the assumption that the debugger can track variable changes. It can't.
It is possible with unmanaged code, the processor has dedicated debug registers that allow setting data breakpoints. Up to three are provided. It generates a hardware interrupt when it sees a particular memory location getting written. This otherwise very useful feature isn't available in managed code however. The garbage collector is completely incompatible with it, it moves objects around, giving them another address.
The managed debugger does support a "when hit" condition on a breakpoint, allowing you to dump info to the output window. That however requires a breakpoint, it cannot be triggered by a change in variable value. It also really slows down code execution since the debugger actually enters a break state before executing the condition.
The obvious place to put such a breakpoint is in a property setter. Which is what you'll need to implement this feature in code. You can do anything you want in that setter, using the Trace class for example.