Cross Domain/Platform Authentication and Data Transfer

using System;
using System.Data;
using System.Data.SqlClient;
using Microsoft.Practices.EnterpriseLibrary.Data;
using System.Data.Common;
using System.Web;
using System.Collections.Specialized;
using System.Text;

/// <summary>
/// Commonly use code for Cross site authentication
/// </summary>
public static class Authentication
{
    public static DataTable VerifyCredentials(string userName, string password)
    {
        //confirm credentials. upone success, return a single record for this user
        return ExecuteDataSet("Customer_Login", new object[] { userName, password }).Tables[0];
    }

    //this method retrieve a complete set of user data that a third party app needs
    public static DataSet RetrieveUserDataSet(int siteID, string userID)
    {
        //siteID determines storedproc name. 
        DataSet ds = ExecuteDataSet(GetDataTransferProc(siteID), new object[] { userID });
        return ds;
    }

    private static string GetDataTransferProc(int siteID)
    {
        string Proc = "";
        SqlDataReader rd = ExecuteDataReader("SiteInfo_GetSiteInfo", new object[] { siteID });
        if (rd.Read())
            Proc = rd["DataTransferProcName"].ToString();
        if (Proc == "")
            throw new Exception("No data transfer sql stored procedure is specified for this site.");

        return Proc;
    }

    public static SqlDataReader ExecuteDataReader(string storedProc, object[] parameters)
    {
        try
        {
            Database db = DatabaseFactory.CreateDatabase();
            DbCommand dbcom = db.GetStoredProcCommand(storedProc, parameters);
            return (SqlDataReader)db.ExecuteReader(dbcom);
        }
        catch
        {
            throw;
        }
    }
    public static int ExecuteNonQuery(string storedProc, object[] parameters)
    {
        Database db = DatabaseFactory.CreateDatabase();
        DbCommand dbcom = db.GetStoredProcCommand(storedProc, parameters);
        return db.ExecuteNonQuery(dbcom);
    }

    public static DataSet ExecuteDataSet(string storedProc, object[] parameters)
    {
        try
        {
            Database db = DatabaseFactory.CreateDatabase();
            DbCommand dbcom = db.GetStoredProcCommand(storedProc, parameters);
            return db.ExecuteDataSet(dbcom);
        }
        catch
        {
            throw;
        }
    }
    //The return url to be used to send user back to partner site needs to be parsed to add the AuthID properly
    public static string WellFormReturnUrl(string originalReturnUrl, string authID)
    {
        string WellFormedUrl = "";
        //check if the original return url has parameters attached already. encryptedParameter has to be UrlEncoded.
        int Position = originalReturnUrl.IndexOf("?");
        if (Position != -1)
        {
            //? exists. original url has some parameters already, append the ecryptedParameter to the end with a "&"
            WellFormedUrl = originalReturnUrl + "&AuthID=" + HttpUtility.UrlEncode(authID);
        }
        else //original url does not have any parameters, append EncryptedData with "?"
        {
            WellFormedUrl = originalReturnUrl + "?AuthID=" + HttpUtility.UrlEncode(authID);
        }
        return WellFormedUrl;
    }
    //Build user data in SqlDataReader into a text string
    public static string SerializeParameters(NameValueCollection userData)
    {
        StringBuilder MyString = new StringBuilder();
        foreach (string k in userData.AllKeys)
        {
            MyString.Append(k);
            MyString.Append('=');
            //for url use, urlencode is required
            MyString.Append(HttpUtility.UrlEncode(userData[k]));//encode chars like '=', &, ' ' etc.
            MyString.Append('&');
        }
        return MyString.ToString();
    }
    //place all user authentication related data into a data collection so that it is easy to handle
    public static NameValueCollection BuildUserDataCollection(DataTable tbl, int minutesToExpire, int siteID, string returnUrl)
    {
        NameValueCollection UserDataCollection = new NameValueCollection();
        DataRow Row = tbl.Rows[0];
        for (int i = 0; i < tbl.Columns.Count; i++)
        {
            //IMPORTANT: in the collection UserID is required.
            UserDataCollection.Add(tbl.Columns[i].ColumnName.ToString(), Row[i].ToString());
        }
        //add expiration
        UserDataCollection.Add("ExpirationDateTime", DateTime.Now.AddMinutes(minutesToExpire).ToString());
        //add siteID
        UserDataCollection.Add("SiteID", siteID.ToString());
        //add returnUrl
        UserDataCollection.Add("ReturnUrl", returnUrl);

        return UserDataCollection;
    }
    public static NameValueCollection DeserializeUserData(string serializedString)
    {
        NameValueCollection UserData = new NameValueCollection();
        string[] NameValuePairs = serializedString.Split('&');
        for (int i = 0; i < NameValuePairs.Length; i++)
        {
            string[] NameValue = NameValuePairs[i].Split('=');

            if (NameValue.Length == 2)
            {
                if (NameValue[0].ToLower() == "expirationdatetime")//replace the default expiration datetime.
                {
                    if (Convert.ToDateTime(HttpUtility.UrlDecode(NameValue[1])) <= DateTime.Now)
                        throw new Exception("The Url has expired.");
                }
                UserData.Add(NameValue[0], HttpUtility.UrlDecode(NameValue[1]));
            }
        }
        return UserData;
    }
}