C# Shiznit - QueryString class useful for querystring manipulation, appendage, etc

QueryString class useful for querystring manipulation, appendage, etc

posted on Wednesday, February 08, 2006 by bobby @ 12:36 pm

13 comments

This little gem allows you to modify the querystring rather simply. Call QueryString.FromCurrent() to get a QueryString object populated from the current context.

Add, remove and edit the collection with ease. Just call .ToString() when you are ready to write it out.

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public class QueryString : NameValueCollection
{
    private string document;

    public string Document
    {
        get
        {
            return document;
        }
    }
    
    public QueryString()
    {
    }

    public QueryString(NameValueCollection clone) : base(clone)
    {
    }

    public static QueryString FromCurrent()
    {
        return FromUrl(HttpContext.Current.Request.Url.AbsoluteUri);    
    }

    public static QueryString FromUrl(string url)
    {
        string[] parts = url.Split("?".ToCharArray());
        QueryString qs = new QueryString();
        qs.document = parts[0];

        if(parts.Length == 1)
            return qs;

        string[] keys = parts[1].Split("&".ToCharArray());

        foreach(string key in keys)
        {
            string[] part = key.Split("=".ToCharArray());

            if(part.Length == 1)
                qs.Add(part[0], "");

            qs.Add(part[0], part[1]);
        }

        return qs;
    }

    public void ClearAllExcept(string except)
    {
        ClearAllExcept(new string[] { except });
    }

    public void ClearAllExcept(string[] except)
    {
        ArrayList toRemove = new ArrayList();
        foreach(string s in this.AllKeys)
        {
            foreach(string e in except)
            {
                if(s.ToLower() == e.ToLower())
                    if(!toRemove.Contains(s))
                        toRemove.Add(s);
            }
        }

        foreach(string s in toRemove)
            this.Remove(s);
    }

    public override void Add(string name, string value)
    {
        if(this[name] != null)
            this[name] = value;
        else
            base.Add(name, value);
    }

    public override string ToString()
    {
        return ToString(false);
    }

    public string ToString(bool includeUrl)
    {
        string[] parts = new string[this.Count];
        string[] keys = this.AllKeys;

        for(int i = 0; i < keys.Length; i++)
            parts[i] = keys[i] + "=" + HttpUtility.UrlEncode(this[keys[i]]);

        string url = String.Join("&", parts);

        if(!string.IsNullOrEmpty(url) && !url.StartsWith("?"))
            url = "?" + url;

        if(includeUrl)
            url = this.document + url;
        
        return url;
    }
}

CommentsComments

Thanks. There is also another one out there that Uwe Keim created. I use that a lot.
http://www.codeproject.com/aspnet/SimpleQueryString.asp

How did you get the code in the Blog nicely formatted? I am a new comer to Blogger, but an old hand in programming.

Well, this is not run by blogger (see here), it's run by my own blogging framework.

The code is formatted w/ the Highlighter .NET component.

Does your class provide a way to access the anchor element ie: #my_anchor

No, I didn't add that in.

Nice, although I would change:



HttpContext.Current.Server.UrlEncode(this[keys[ i ]]);



HttpUtility.UrlEncode(this[keys[ i ]]);

because the context might not always be available for a request, such as when processing a request through an HttpModule or an asynchronous call.

Agreed. Good find. Fixed.

Senixon's inquiry concerning access to the anchor element of the url is also what I was interested in. DDL in Flash using .NET would be a breeze with this QueryString class, however a lot of DDL solutions that developers come up with are based on the use of anchors. Any plans to implement such functionality into this class?

...

Very handy! However have you tested your ClearExcept method? I have qs variable p that I want kept so I called ClearExcept("p") and it was the only thing removed!!
So I rewrote it to this:



public QueryString ClearAllExcept(string[] except)

    {

        foreach (string s in this.AllKeys)

            {

                bool remove = true;

                foreach (string e in except)

                {

                    if (s.ToLower() == e.ToLower())

                    {

                        remove = false;

                        break;

                    }

                }

                if (remove) this.Remove(s);

            }

            return this;

        }

Either we've got symantic differences or I don't think the method in your post will do what it sounds like it should

Also I changed all of the return values of void to return the current QueryString. That way you can use it very similarly to the string class.
eg:



string bob = QueryString.GetCurrent().ClearExcept("p").Add("q", 1).ToString();

Also, I overloaded the add method to take an int in the second parameter as so often variables in qs' are ints. Probably can do something clever with generics there but was in a hurry.

Cheers!

I realize this is 2+ years after you wrote it, but you should consider a StringBuilder for performance in ToString() implementation. All those string concatenations are killers.

Additionally, in ClearAllExcept(), instead of s.ToLower() == e.ToLower() consider:


                if( s.Equals(e, StringComparison.InvariantCultureIgnoreCase) )

It's more portable, explicit, avoids 2 extra string allocations, and is probably faster.

This solution has a small bug when working with encrypted parameteres in the QueryString.

Using this line, will fix this problem:
string[] part = key.Split("=".ToCharArray(), 2);

Adding this will allow you to derive the value of a selected key value pair

public string GetValue(string sKey)
{
string sOut = "";
if (this[sKey] == null)
{ }
else
{
sOut = this[sKey];
}
return sOut;
}

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