Реализовал хранение писем в списке

SecuritySystem/SecuritySystemListImplement/DataListSingleton.cs

@@ -10,6 +10,7 @@ namespace SecuritySystemListImplement
         public List<Secure> Secures { get; set; }
         public List<Client> Clients { get; set; }
         public List<Implementer> Implementers { get; set; }
+        public List<MessageInfo> MessageInfos { get; set; }
         private DataListSingleton()
         {
             Components = new List<Component>();
@@ -17,6 +18,7 @@ namespace SecuritySystemListImplement
             Secures = new List<Secure>();
             Clients = new List<Client>();
             Implementers = new List<Implementer>();
+            MessageInfos = new List<MessageInfo>();
         }
         public static DataListSingleton GetInstance()
         {

SecuritySystem/SecuritySystemListImplement/Implements/MessageInfoStorage.cs

@@ -0,0 +1,45 @@
+using SecuritySystemContracts.BindingModels;
+using SecuritySystemContracts.SearchModels;
+using SecuritySystemContracts.StoragesContracts;
+using SecuritySystemContracts.ViewModels;
+
+namespace SecuritySystemListImplement.Implements
+{
+    public class MessageInfoStorage : IMessageInfoStorage
+    {
+        private readonly DataListSingleton _source;
+        public MessageInfoStorage(DataListSingleton source)
+        {
+            _source = source;
+        }
+
+        public MessageInfoViewModel? GetElement(MessageInfoSearchModel model)
+        {
+            return GetFilteredList(model).FirstOrDefault();
+        }
+
+        public List<MessageInfoViewModel> GetFilteredList(MessageInfoSearchModel model)
+        {
+            var messageInfos = GetFullList();
+            if (!string.IsNullOrEmpty(model.MessageId))
+            {
+                messageInfos = messageInfos.Where(x => x.MessageId == model.MessageId).ToList();
+            }
+            if (model.ClientId != null)
+            {
+                messageInfos = messageInfos.Where(x => x.ClientId == model.ClientId).ToList();
+            }
+            return messageInfos;
+        }
+
+        public List<MessageInfoViewModel> GetFullList()
+        {
+            return _source.MessageInfos.Select(x => x.GetViewModel).ToList();
+        }
+
+        public MessageInfoViewModel? Insert(MessageInfoBindingModel model)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}

SecuritySystem/SecuritySystemListImplement/Models/MessageInfo.cs

@@ -0,0 +1,55 @@
+using SecuritySystemContracts.BindingModels;
+using SecuritySystemContracts.ViewModels;
+using SecuritySystemDataModels.Models;
+using System.Reflection;
+
+namespace SecuritySystemListImplement.Models
+{
+    public class MessageInfo : IMessageInfoModel
+    {
+        public string MessageId { get; set; } = string.Empty;
+        public int? ClientId { get; set; }
+        public string SenderName { get; set; } = string.Empty;
+        public DateTime DateDelivery { get; set; } = DateTime.Now;
+        public string Subject { get; set; } = string.Empty;
+        public string Body { get; set; } = string.Empty;
+
+        public static MessageInfo? Create(MessageInfoBindingModel? model)
+        {
+            if (model == null)
+            {
+                return null;
+            }
+            return new MessageInfo()
+            {
+                MessageId = model.MessageId,
+                ClientId = model.ClientId,
+                SenderName = model.SenderName,
+                DateDelivery = model.DateDelivery,
+                Subject = model.Subject,
+                Body = model.Body,
+            };
+        }
+        public void Update(MessageInfoBindingModel? model)
+        {
+            if (model == null)
+            {
+                return;
+            }
+            ClientId = model.ClientId;
+            SenderName = model.SenderName;
+            DateDelivery = model.DateDelivery;
+            Subject = model.Subject;
+            Body = model.Body;
+        }
+        public MessageInfoViewModel GetViewModel => new()
+        {
+            MessageId = MessageId,
+            ClientId = ClientId,
+            SenderName = SenderName,
+            DateDelivery = DateDelivery,
+            Subject = Subject,
+            Body = Body,
+        };
+    }
+}