Add New Query Strings to Existing URL in C# and Redirect to it

Question

Can anybody help me with the c# code to add two query strings to an existing URL. URL typically looks like this below. When the URL is created in c# to redirect to it as well. Any help much appreciated.

http://localhost/somesite/index.php?Filename=somefile.txt&Filepath=E:\myfolder

Answer 1

to build up url would be option A: (string concat)

string param1 = "Filename=somefile.txt";
    string param2 = @"Filepath=E:\myfolder";
    Uri YourURL = new Uri($"http://localhost/somesite/index.php?{param1}&{param2}");
    Console.WriteLine(YourURL);

Option b: (URIBuilder)

UriBuilder uriBuilder = new UriBuilder();
    uriBuilder.Scheme = "http";
    uriBuilder.Host = "localhost";
    uriBuilder.Path = "somesite/index.php";
    //uriBuilder.Port = 80;
    
    var q = new Dictionary<string,string>();
    q.Add("Filename","somefile.txt");
    q.Add("Filepath","E:\\myfolder");
    uriBuilder.Query = string.Join("&", q.Select(s => $"{s.Key}={s.Value}").ToList());
    uriBuilder.ToString().Dump();

to redirect. not sure what are you using for UI. the question is very blur. but to redirect try this:

Response.Redirect(YourURL);

otherwise, please rewrite your question with better explanation