Question

I need to use in my asp.net project a stack collection created inside a class

public class ExpressionsEvaluator
{
    public Stack<ExpressionParameter> expressionParameters = new Stack<ExpressionParameter>();

    public object EvaluateExpression()
    {
        // calculate expression patamers
        expressionParameters.Push(parameter);

        // Do some functions

        // remove the last parameters
        expressionParameters.Pop();
    }
}

Is this approach thread safe?

Will the expressionParameters object be different for each user accessing the website?

Use case:

    public ActionResult EvaluateExpression(string expression)
    {
        try
        {
            ExpressionsEvaluator expressionEvaluator = new ExpressionsEvaluator();
            object result = expressionEvaluator.EvaluateExpression(expression);
            return Json(result, JsonRequestBehavior.AllowGet);
        }
        catch (Exception ex)
        {
            return Json(new { hasError = true }, JsonRequestBehavior.AllowGet);
        }
    }

Answer 1

Is this approach thread safe?

Yes, the class in itself is thread-safe. It’s how you use it.

Will the expressionParameters object be different for each user
accessing the website?

That depends how you use it, and where you store it. If you create an instance of it in a web-page, than it will be a total new instance for each page-request. If you create an instance but store it somewhere, than it depends how that storage works. If you use a session, than yes, each user has its own instance.