using System;

using System.Text;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var dictionary = new Dictionary<string, string>

        {

            ["Key1"] = "Value1",

            ["Key2"] = "Value2",

            ["Key3"] = "Value",

        };

        var list = new List<KeyValuePair<string, string>>(dictionary);

        var url = "test.com";

        Console.WriteLine($"Using dictionary: {JoinUrlQuery(url, dictionary)}");

        Console.WriteLine($"Using list: {JoinUrlQuery(url, list)}");

    }

    public static string JoinUrlQuery(string url, IEnumerable<KeyValuePair<string, string>> source, string keyValuePairSeparator = "&", string keyValueSeparator = "=", bool urlEncode = false)

    {

        var builder = new StringBuilder();

​

        foreach (var (key, value) in source)

        {

            builder.Append($"{key}{keyValueSeparator}{(urlEncode ? Uri.EscapeDataString(value) : value)}{keyValuePairSeparator}");

        }

        builder.Length -= 1;

​

        return $"{url}?{builder}";

    }

}