Append key value pairs to query string

Question

I want to add multiple query string key value pairs to an url by formatting a regular string and then appending this to the current query string. Because, in my knowledge, there is no way to change the actual Request.QueryString. Therefore I try to append the kvp:s to the query string as per below. I have searched StackOverflow, but I couldn't find an answer that matches my problem.

protected void ServiceSelectionChanged(object sender, EventArgs e)
{
    var regNr = registrationNumber.Text;
    var selectedServiceType = SelectedServiceType.ToString("D");

    string url = string.Empty;
    BookingHelpers.FormatQueryStringUrl(this.Request, "serviceType", selectedServiceType, ref url);
    BookingHelpers.FormatQueryStringUrl(this.Request, "regNr", regNr, ref url);
    Server.Transfer(url, false);
}

public static void FormatQueryStringUrl(HttpRequest request, string key, string value, ref string url)
{
    if (string.IsNullOrEmpty(url))
    {
        url = request.Url.PathAndQuery; 
    }
    if (url.Contains("?"))
    {
        if (url.Contains("&" + key))
        {
            string currentValue = request.QueryString[key];
            url = url.Replace("&" + key + "=" + currentValue, "&" + key + "=" + value);
        }
        else
        {
            url = String.Format(request.Url.PathAndQuery + "&" + key + "={0}", value);
        }
    }
    else url = String.Format(request.Url.PathAndQuery + "?" + key + "={0}", value);
}

This however uses the Request.QueryString each time, so the first kvp is overwritten. So my question is: How can I make this work so that i can append both of the key value pairs to the query string?

why can't you construct an object and serialize and send it as JSON string if it is less characters.. — Saravanan, Jan 23 '15 at 07:57

score 0 · Accepted Answer · edited May 23 '17 at 10:28

I found an answer on stack overflow that helped me:

How to build a query string for a URL in C#?

Although, I also needed to check if the url already had a query string in it, so i modified it to something like this.

public static string ToQueryString(string url, NameValueCollection nvc)
    {
        StringBuilder sb;

        if (url.Contains("?"))
            sb = new StringBuilder("&");
        else
            sb = new StringBuilder("?");

        bool first = true;

        foreach (string key in nvc.AllKeys)
        {
            foreach (string value in nvc.GetValues(key))
            {
                if (!first)
                {
                    sb.Append("&");
                }

                sb.AppendFormat("{0}={1}", Uri.EscapeDataString(key), Uri.EscapeDataString(value));

                first = false;
            }
        }

        return url + sb.ToString();
    }

And the usage instead became:

var queryParams = new NameValueCollection() 
{
    { "isaServiceType", selectedIsaServiceType },
    { "regNr", regNr }
};

var url = ToQueryString(Request.Url.PathAndQuery, queryParams);

Append key value pairs to query string

1 Answers1