Creates a content type based on the specified schema in SharePoint 2010

SPContentTypeExtensions.cs

namespace Deployment.ContentType
{
    /// <summary>
    /// Content Type 
    /// </summary>
    public static class SPContentTypeExtensions
    {
        /// <summary>
        /// Creates a content type based on the specified schema.
        /// </summary>
        /// <returns>
        /// An instance of the new content type.
        /// </returns>
        /// <param name="contentTypes">Content Type collection</param>
        /// <param name="schemaXml">A Collaborative Application Markup Language (CAML) string that contains the schema.</param>
        public static SPContentType AddContentTypeAsXml(this SPContentTypeCollection contentTypes, string schemaXml)
        {
            SPContentType contentType;
            using (var xrdr = new XmlTextReader(new StringReader(schemaXml)))
            {
                xrdr.ProhibitDtd = true;
                contentType = contentTypes.CreateContentType();
                LoadXmlInternal(contentType, xrdr);
                contentTypes.Add(contentType);
            }
            return contentType;
        }



        /// <summary>
        /// Create content type
        /// </summary>
        /// <param name="contentTypes"></param>
        /// <returns></returns>
        private static SPContentType CreateContentType(this SPContentTypeCollection contentTypes)
        {
            var constructor = (typeof(SPContentType)).GetConstructor(
                BindingFlags.NonPublic | BindingFlags.Instance,
                null,
                Type.EmptyTypes,
                null);

            var contentType = (SPContentType)constructor.Invoke(new object[0]);
            contentType.SetWeb(contentTypes.GetWeb());
            return contentType;
        }

        /// <summary>
        /// Load schema for content type 
        /// </summary>
        /// <param name="contentType"></param>
        /// <param name="xmlReader"></param>
        private static void LoadXmlInternal(SPContentType contentType, XmlReader xmlReader)
        {
            var loadMethod = contentType.GetType().GetMethod("Load",
                BindingFlags.NonPublic | BindingFlags.Instance,
                null,
                new[] { typeof(XmlReader) },
                null);
            loadMethod.Invoke(contentType, new object[] { xmlReader });
        }

        private static SPWeb GetWeb(this SPContentTypeCollection contentTypes)
        {
            var webProp = typeof(SPContentTypeCollection).GetProperty("Web", BindingFlags.NonPublic | BindingFlags.Instance);
            return  (SPWeb)webProp.GetValue(contentTypes, null);
        }


        private static void SetWeb(this SPContentType contentType,SPWeb web)
        {
            var webProp = typeof(SPContentType).GetProperty("Web", BindingFlags.NonPublic | BindingFlags.Instance);
            webProp.SetValue(contentType, web, null);
        }
    }
}