How to check that Request.QueryString has a specific value or not in ASP.NET?

Question

I have an error.aspx page. If a user comes to that page then it will fetch the error path in page_load() method URL using Request.QueryStrin

Answer 1

string.IsNullOrEmpty(Request.QueryString["aspxerrorpath"]) //true -> there is no value

Will return if there is a value