A simple XML minifier in C#.

XMLMinifier.cs

using System.IO;
using System.Text;
using System.Xml;

namespace XMLMinifier
{
    /// <summary>
    /// Config object for the XML minifier.
    /// </summary>
    public class XMLMinifierSettings
    {
        public bool RemoveEmptyLines { get; set; }
        public bool RemoveWhitespaceBetweenElements { get; set; }
        public bool CloseEmptyTags { get; set; }
        public bool RemoveComments { get; set; }

        public static XMLMinifierSettings Aggressive
        {
            get
            {
                return new XMLMinifierSettings 
                { 
                    RemoveEmptyLines = true, 
                    RemoveWhitespaceBetweenElements = true, 
                    CloseEmptyTags = true, 
                    RemoveComments = true 
                };
            }
        }

        public static XMLMinifierSettings NoMinification
        {
            get
            {
                return new XMLMinifierSettings 
                { 
                    RemoveEmptyLines = false, 
                    RemoveWhitespaceBetweenElements = false, 
                    CloseEmptyTags = false, 
                    RemoveComments = false 
                };
            }
        }
    }

    /// <summary>
    /// XML minifier. No Regex allowed! ;-)
    /// 
    /// Example)
    ///     var sampleXml = File.ReadAllText("somefile.xml");
    ///     var minifiedXml = new XMLMinifier(XMLMinifierSettings.Aggressive).Minify(sampleXml);
    /// </summary>
    public class XMLMinifier
    {
        private XMLMinifierSettings _minifierSettings;

        public XMLMinifier(XMLMinifierSettings minifierSettings)
        {
            _minifierSettings = minifierSettings;
        }

        public string Minify(string xml)
        {
            var originalXmlDocument = new XmlDocument();
            originalXmlDocument.PreserveWhitespace = !(_minifierSettings.RemoveWhitespaceBetweenElements || _minifierSettings.RemoveEmptyLines);
            originalXmlDocument.Load(new MemoryStream(Encoding.UTF8.GetBytes(xml)));

            //remove comments first so we have less to compress later
            if (_minifierSettings.RemoveComments)
            {
                foreach (XmlNode comment in originalXmlDocument.SelectNodes("//comment()"))
                {
                    comment.ParentNode.RemoveChild(comment);
                }
            }

            if (_minifierSettings.CloseEmptyTags)
            {
                foreach (XmlElement el in originalXmlDocument.SelectNodes("descendant::*[not(*) and not(normalize-space())]"))
                {
                    el.IsEmpty = true;
                }
            }

            if (_minifierSettings.RemoveWhitespaceBetweenElements)
            {
                return originalXmlDocument.InnerXml;
            }
            else
            {
                var minified = new MemoryStream();
                originalXmlDocument.Save(minified);

                return Encoding.UTF8.GetString(minified.ToArray());
            }
        }
    }
}

Good work, We have created online XML formatter, built in C#.
Will definitely add more tool on website using above functionality to minify XML, thanks.