вроде реализовала третье хранилище уфф

SushiBarDatabaseImplement/Implements/MessageInfoStorage.cs

@@ -0,0 +1,60 @@
+using Microsoft.EntityFrameworkCore;
+using SushiBarContracts.BindingModel;
+using SushiBarContracts.SearchModel;
+using SushiBarContracts.StoragesContracts;
+using SushiBarContracts.ViewModels;
+using SushiBarDatabaseImplement.Models;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace SushiBarDatabaseImplement.Implements
+{
+    public class MessageInfoStorage : IMessageInfoStorage
+    {
+        public MessageInfoViewModel? GetElement(MessageInfoSearchModel model)
+        {
+            using var context = new SushiBarDatabase();
+            if(string.IsNullOrEmpty(model.MessageId)) return null;
+            return context.Messages
+                .Include(x => x.Client)
+                .FirstOrDefault(x => x.MessageId == model.MessageId)?
+                .GetViewModel;
+        }
+
+        public List<MessageInfoViewModel> GetFilteredList(MessageInfoSearchModel model)
+        {
+            using var context = new SushiBarDatabase();
+            if (model.ClientId.HasValue)
+            {
+                return context.Messages
+                    .Include(x => x.Client)
+                    .Where(x => x.ClientId == model.ClientId)
+                    .Select(x => x.GetViewModel)
+                    .ToList();
+            }
+            return new();
+        }
+
+        public List<MessageInfoViewModel> GetFullList()
+        {
+            using var context = new SushiBarDatabase();
+            return context.Messages
+                .Include(x => x.Client)
+                .Select(x => x.GetViewModel)
+                .ToList();
+        }
+
+        public MessageInfoViewModel? Insert(MessageInfoBindingModel model)
+        {
+            using var context = new SushiBarDatabase();
+            var newMessage = MessageInfo.Create(model);
+            if(newMessage == null) return null;
+            context.Messages.Add(newMessage);
+            context.SaveChanges();
+            return newMessage.GetViewModel;
+        }
+    }
+}

SushiBarDatabaseImplement/Models/MessageInfo.cs

@@ -0,0 +1,53 @@
+using SushiBarContracts.BindingModel;
+using SushiBarContracts.ViewModels;
+using SushiBarDataModels;
+using System.ComponentModel.DataAnnotations;
+
+namespace SushiBarDatabaseImplement.Models
+{
+    public class MessageInfo : IMessageInfoModel
+    {
+        [Key]
+        public string MessageId { get; set; } = string.Empty;
+
+        public int? ClientId { get; set; }
+
+        [Required]
+        public string SenderName { get; set; } = string.Empty;
+
+        [Required]
+        public DateTime DateDelivery { get; set; } = DateTime.Now;
+
+        [Required]
+        public string Subject { get; set; } = string.Empty;
+
+        [Required]
+        public string Body { get; set; } = string.Empty;
+
+        public virtual Client? Client { get; set; }
+
+        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 MessageInfoViewModel GetViewModel => new()
+        {
+            MessageId = MessageId,
+            ClientId = ClientId,
+            SenderName = SenderName,
+            DateDelivery = DateDelivery,
+            Subject = Subject,
+            Body = Body,
+        };
+    }
+}

SushiBarDatabaseImplement/SushiBarDatabase.cs

@@ -26,5 +26,6 @@ namespace SushiBarDatabaseImplement
         public virtual DbSet<Order> Orders { set; get; }
         public virtual DbSet<Client> Clients { set; get; }
         public virtual DbSet<Implementer> Implementers { set; get; }
+        public virtual DbSet<MessageInfo> Messages { set; get; }
     }
 }