How to enter the result of a script into a variable?

Question

C++ / C#

Like I'm running js, but how can I put some value of the result into a variable?
Tipo:

var element = document.getElementById("povar").textContent;

and how is it in C# to a variable
Now like this:

string script = "var element = document.getElementById('povar').textContent;";
            browser.ExecuteScriptAsync(script);