My own Mailinator in 5 minutes

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;

namespace LumiSoft.Net.SIP.Message
{
    /// <summary>
    /// Implements SIP "From" value. Defined in RFC 3261.
    /// The From header field indicates the initiator of the request.
    /// </summary>
    /// <remarks>
    /// <code>
    /// RFC 3261 Syntax:
    ///     From       = ( name-addr / addr-spec ) *( SEMI from-param )
    ///     from-param = tag-param / generic-param
    ///     tag-param  = "tag" EQUAL token
    /// </code>
    /// </remarks>
    public class SIP_t_From : SIP_t_ValueWithParams
    {
        private SIP_t_NameAddress m_pAddress = null;

        /// <summary>
        /// Default constructor.
        /// </summary>
        /// <param name="value">From: header field value.</param>
        public SIP_t_From(string value)
        {
            m_pAddress = new SIP_t_NameAddress();

            Parse(new StringReader(value));
        }

        /// <summary>
        /// Default constructor.
        /// </summary>
        /// <param name="address">From address.</param>
        public SIP_t_From(SIP_t_NameAddress address)
        {
            m_pAddress = address;
        }


        #region method Parse

        /// <summary>
        /// Parses "From" from specified value.
        /// </summary>
        /// <param name="value">SIP "accept-range" value.</param>
        /// <exception cref="ArgumentNullException">Raised when <b>value</b> is null.</exception>
        /// <exception cref="SIP_ParseException">Raised when invalid SIP message.</exception>
        public void Parse(string value)
        {
            if(value == null){
                throw new ArgumentNullException("value");
            }

            Parse(new StringReader(value));
        }

        /// <summary>
        /// Parses "From" from specified reader.
        /// </summary>
        /// <param name="reader">Reader from where to parse.</param>
        /// <exception cref="ArgumentNullException">Raised when <b>reader</b> is null.</exception>
        /// <exception cref="SIP_ParseException">Raised when invalid SIP message.</exception>
        public override void Parse(StringReader reader)
        {
            /*  From       = ( name-addr / addr-spec ) *( SEMI from-param )
                from-param = tag-param / generic-param
            */

            if(reader == null){
                throw new ArgumentNullException("reader");
            }

            // Parse address
            m_pAddress.Parse(reader);

            // Parse parameters
            ParseParameters(reader);
        }

        #endregion

        #region method ToStringValue

        /// <summary>
        /// Converts this to valid "From" value.
        /// </summary>
        /// <returns>Returns "From" value.</returns>
        public override string ToStringValue()
        {
            StringBuilder retVal = new StringBuilder();           
            retVal.Append(m_pAddress.ToStringValue()); 
            retVal.Append(this.ParametersToString());

            return retVal.ToString();
        }

        #endregion


        #region Properties Implementation
                
        /// <summary>
        /// Gets address.
        /// </summary>
        public SIP_t_NameAddress Address
        {
            get{ return m_pAddress; }
        }

        /// <summary>
        /// Gets or sets tag parameter value.
        /// The "tag" parameter serves as a general mechanism for dialog identification.
        /// Value null means that tag paramter doesn't exist.
        /// </summary>
        public string Tag
        {
            get{ 
                SIP_Parameter parameter = this.Parameters["tag"];
                if(parameter != null){
                    return parameter.Value;
                }
                else{
                    return null;
                }
            }

            set{                
                if(string.IsNullOrEmpty(value)){
                    this.Parameters.Remove("tag");
                }
                else{
                    this.Parameters.Set("tag",value);
                }
            }
        }

        #endregion

    }
}