How can I convert list class to class array

public class PGNsegmentTxMap
    {

         string pgn;
         public string segmentTx { get; set; }
        

         
         public string PGN
         {
             get
             {
                 if (!String.IsNullOrEmpty(pgn))
                     return pgn.ToUpper();
                 else
                     return string.Empty;
             }

             set { pgn = value; }
         }
        public PGNsegmentTxMap(string pgn, string segmentTx)
        {
            this.segmentTx = segmentTx;
            this.pgn = pgn;
        }
    }

     #endregion





     class ProductComparer : IEqualityComparer<PGNsegmentTxMap>
     {
         // Products are equal if their names and product numbers are equal. 
         public bool Equals(PGNsegmentTxMap x, PGNsegmentTxMap y)
         {

             //Check whether the compared objects reference the same data. 
             if (Object.ReferenceEquals(x, y)) return true;

             //Check whether any of the compared objects is null. 
             if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
                 return false;

             //Check whether the products' properties are equal. 
             return x.segmentTx == y.segmentTx && x.PGN == y.PGN;
         }
         public int GetHashCode(PGNsegmentTxMap product)
         {
             //Check whether the object is null 
             if (Object.ReferenceEquals(product, null)) return 0;

             //Get hash code for the Name field if it is not null. 
             int hashProductName = product.segmentTx == null ? 0 : product.segmentTx.GetHashCode();

             //Get hash code for the Code field. 
             int hashProductCode = product.PGN.GetHashCode();

             //Calculate the hash code for the product. 
             return hashProductName ^ hashProductCode;
         }

         

     }