...

Shared/DTOs/PromotionDetailDto.cs

@@ -11,8 +11,8 @@ namespace Shared.DTOs
         public int ID { get; set; }
         public int PermissionID { get; set; }
         public string PermissionTitle { get; set; }
-        public int CreditAmount { get; set; }
-        public decimal APrice { get; set; }
+        public int CreditAmount { get; set; } 
+        public decimal APrice { get; set; } 
         public decimal TPrice { get { return APrice * CreditAmount; } }
     }
 }

Shared/DTOs/PromotionDto.cs

@@ -10,6 +10,7 @@ namespace Shared.DTOs
     {
         public int ID { get; set; }
         public string Name { get; set; }
+        public decimal TotalPrice { get { return promotionDetails==null ? 0 : promotionDetails.Sum(s => s.TPrice); } }
         public ICollection<PromotionDetailDto> promotionDetails { get; set; }
     }
 }