using System;

using System.Collections.Generic;

using Microsoft.AspNetCore.WebUtilities;

public class Program

{

    public static void Main()

    {

        var exampleUri = new Uri("https://example.com/");

        var requestUri = QueryHelpers.AddQueryString(exampleUri.AbsoluteUri, new Dictionary<string,string>{

            { "myvar1", 123.ToString() },

            { "myvar2", "hello world" }

        });

        Console.WriteLine(requestUri);

    }

}