Portable Class Library (PCL) Version Of HttpUtility.ParseQueryString

Question

Is there a Portable Class Library (PCL) version Of HttpUtility.ParseQueryString contained in System.Web or some code I could use? I want to read a very complex URL.

Answer 1

HttpUtility.ParseQueryString returns HttpValueCollection (Internal Class) which inherits from NameValueCollection. NameValueCollection is a collection of key value pairs like a dictionary but it supports duplicates, maintains order and only implements IEnumerable (This collection is pre-generics). NameValueCollection is not supported in PCL.

My solution (Partly lifted and modified from the .NET framework) is to substitute HttpValueCollection with Collection<HttpValue> where HttpValue is just a key value pair.

public sealed class HttpUtility
{
    public static HttpValueCollection ParseQueryString(string query)
    {
        if (query == null)
        {
            throw new ArgumentNullException("query");
        }

        if ((query.Length > 0) && (query[0] == '?'))
        {
            query = query.Substring(1);
        }

        return new HttpValueCollection(query, true);
    }
}

public sealed class HttpValue
{
    public HttpValue()
    {
    }

    public HttpValue(string key, string value)
    {
        this.Key = key;
        this.Value = value;
    }

    public string Key { get; set; }
    public string Value { get; set; }
}

public class HttpValueCollection : Collection<HttpValue>
{
    #region Constructors

    public HttpValueCollection()
    {
    }

    public HttpValueCollection(string query)
        : this(query, true)
    {
    }

    public HttpValueCollection(string query, bool urlencoded)
    {
        if (!string.IsNullOrEmpty(query))
        {
            this.FillFromString(query, urlencoded);
        }
    } 

    #endregion

    #region Parameters

    public string this[string key]
    {
        get { return this.First(x => string.Equals(x.Key, key, StringComparison.OrdinalIgnoreCase)).Value; }
        set { this.First(x => string.Equals(x.Key, key, StringComparison.OrdinalIgnoreCase)).Value = value; }
    }

    #endregion

    #region Public Methods

    public void Add(string key, string value)
    {
        this.Add(new HttpValue(key, value));
    }

    public bool ContainsKey(string key)
    {
        return this.Any(x => string.Equals(x.Key, key, StringComparison.OrdinalIgnoreCase));
    }

    public string[] GetValues(string key)
    {
        return this.Where(x => string.Equals(x.Key, key, StringComparison.OrdinalIgnoreCase)).Select(x => x.Value).ToArray();
    }

    public void Remove(string key)
    {
        this.Where(x => string.Equals(x.Key, key, StringComparison.OrdinalIgnoreCase))
            .ToList()
            .ForEach(x => this.Remove(x));
    }

    public override string ToString()
    {
        return this.ToString(true);
    }

    public virtual string ToString(bool urlencoded)
    {
        return this.ToString(urlencoded, null);
    }

    public virtual string ToString(bool urlencoded, IDictionary excludeKeys)
    {
        if (this.Count == 0)
        {
            return string.Empty;
        }

        StringBuilder stringBuilder = new StringBuilder();

        foreach (HttpValue item in this)
        {
            string key = item.Key;

            if ((excludeKeys == null) || !excludeKeys.Contains(key))
            {
                string value = item.Value;

                if (urlencoded)
                {
                    // If .NET 4.5 and above (Thanks @Paya)
                    key = WebUtility.UrlDecode(key);
                    // If .NET 4.0 use this instead.
                    // key = Uri.EscapeDataString(key);
                }

                if (stringBuilder.Length > 0)
                {
                    stringBuilder.Append('&');
                }

                stringBuilder.Append((key != null) ? (key + "=") : string.Empty);

                if ((value != null) && (value.Length > 0))
                {
                    if (urlencoded)
                    {
                        value = Uri.EscapeDataString(value);
                    }

                    stringBuilder.Append(value);
                }
            }
        }

        return stringBuilder.ToString();
    } 

    #endregion

    #region Private Methods

    private void FillFromString(string query, bool urlencoded)
    {
        int num = (query != null) ? query.Length : 0;
        for (int i = 0; i < num; i++)
        {
            int startIndex = i;
            int num4 = -1;
            while (i < num)
            {
                char ch = query[i];
                if (ch == '=')
                {
                    if (num4 < 0)
                    {
                        num4 = i;
                    }
                }
                else if (ch == '&')
                {
                    break;
                }
                i++;
            }
            string str = null;
            string str2 = null;
            if (num4 >= 0)
            {
                str = query.Substring(startIndex, num4 - startIndex);
                str2 = query.Substring(num4 + 1, (i - num4) - 1);
            }
            else
            {
                str2 = query.Substring(startIndex, i - startIndex);
            }

            if (urlencoded)
            {
                this.Add(Uri.UnescapeDataString(str), Uri.UnescapeDataString(str2));
            }
            else
            {
                this.Add(str, str2);
            }

            if ((i == (num - 1)) && (query[i] == '&'))
            {
                this.Add(null, string.Empty);
            }
        }
    } 

    #endregion
}

UPDATE

Updated so that HttpValueCollection now inherits from Collection rather than List as highlighted in the comments.

UPDATE 2

Updated to use WebUtility.UrlDecode if using .NET 4.5, thanks to @Paya.