Convert

 class Applicationdata
 {
   private static ArrayList listxvalue; 
   static Applicationdata()               
        {          
                       listxvalue = new ArrayList();
          }
   public static ArrayList Listxvalue
        {
            get { return listxvalue; }
        }
} 
// In the main fun
     double[,] transxvalue;
     double[,] xvalue = obtain value from the constructor;
     Applicationdata.Listxvalue.Add(xvalue); // save xvalue into the Listxvalue

     transxvalue = (double[,])Applicationdata.Listxvalue[0];  // Get the value back from Listxvalue.
                                         -----------------------------ArrayList
                         ----------- Convert from ArrayList to double[,] type