Replace item in querystring

Question

I have a URL that also might have a query string part, the query string might be empty or have multiple items.

I want to replace one of the items in the query string

Answer 1

Lets have this url: https://localhost/video?param1=value1

At first update specific query string param to new value:

var uri = new Uri("https://localhost/video?param1=value1");
var qs = HttpUtility.ParseQueryString(uri.Query);
qs.Set("param1", "newValue2");

Next create UriBuilder and update Query property to produce new uri with changed param value.

var uriBuilder = new UriBuilder(uri);
uriBuilder.Query = qs.ToString();
var newUri = uriBuilder.Uri;

Now you have in newUri this value: https://localhost/video?param1=newValue2