How to find string length with out using string length function

More homework, I suspect. Start by trying to analyze the problem and figure out what you need to do in real world terms to get the result, then turn that into code. For example how would you calculate the length of this sentence; oh hold on there's some more here ...

Why? Anyway, if it's not cheating you can convert it to a character array and return the length of that instead

int length = "Test string".ToCharArray().Length;

I would count the characters...
i.e. dumb question => dumb answer.
:)

That's a fairly strange request. If you want to do it the C way, then iterate through every character until you hit \0. You could also use aspdotnetdev's way. But chances are that the .Net framework can do things far more efficiently.

Use the all-powerful LiquidNitrogen object.

I see from your profile that you're working as a developer, so I assume this is not homework. It's attracted a lot of joke answers because it seems like a dumb question - the string class has a length property, so why not use it ? In my experience, people who ask questions like this, have a reason that is not immediately clear for asking them. You should edit your post to explain what it is you're trying to do, because usually, when people do that, the solution is not what they expected it to be, and we can only help with that, if you explain your motives.