string baseUrl = "https://example.com/path/to/resource"; string parameterName = "key"; string parameterValue = "value"; // Use AppendQuery method to add query string parameters string urlWithQuery = baseUrl.AppendQuery(parameterName, parameterValue); Console.WriteLine(urlWithQuery); // Output: https://example.com/path/to/resource?key=valueIn the above example, we first define the base URL for our resource. Then we define a parameter name and value that we want to add to the URL as a query string. Finally, we use the AppendQuery method to append the query string to the base URL and get the final URL with the query string. This method is useful when building URLs dynamically for APIs, websites or web applications. The package library for this method is `System.Web`.