* Separated the application into 4 parts: Application.Client, Application.Core, Application.DataAccessLayer, Application.BusinessLogicLayer.

* Application.DataAccessLayer:
  * Includes the DataBase Contexts (Write and Read Contexts).
  * Includes every DataBase Entities.
  * Includes DesignTimeDbContextFactory for generating database tables at design-time.
  * Includes Extensions for DataBase Context (you can see more information about this in: ParkingAppDbContextExtension.InitDatabase method).
  * Includes generated Database Migrations.
* Application.Core:
  * This project includes all elements that can be used by any point in the application.
  * This project does not include any business logic.
  * Includes the general global error handling constants and models for the client application.
  * Includes Command and Query interfaces for MediatR.
  * Includes a global export abstraction and a JSON Export Service that implements this abstraction.
  * Includes the types for environment.
  * Includes static datasets (for example: environment variables).
* Application.BusinessLogicLayer:
  * This project includes the Business Logic.
  * The business logic can be divided into modules.
  * The module folders contain the following: Commands- Querys with Handlers, Dtos, Services with Interfaces and Request- Response Models for Client Application Commands.
  * Includes the Command and Query abstractions for MediatR.
* Application.Client:
  * This is the User Interface Layer.
  * Includes IoC DI Registers, with separate configuration files (for example: DataBase configurations, MediatR configurations, Scoped and Singleton services , etc.).
  * Includes each extension for the IoC DI (for example: Hosts, etc.).
  * Includes configuration settings for NLog.
  * Includes the ASPNETCORE_ENVIRONMENT environment variable configuration.
  * Includes starting the database migration when starting the application.
  * Includes client-side global error handling.
    * The unhandled errors appear in an error window.
    * The text that appears depends on whether the application is running in a developer or other environment.
  * Includes the RelayCommandAsync class that implements the ICommand interface.
  * Includes the ViewModelBase class that implements the INotifyPropertyChange interface.
  * Includes the windows, views, view models and commands that used by the client application.
  * Includes the services that used by the client application.

* The application implements the following business logic:
  * The application stores data from a parking garage system.
    * The system stores the arrival and departure times.
    * The system stores the parking passes. There are two types of parking passes:
      * License Plate based (1 car).
      * Card based (1 card - up to several cars).
    * In case of a key partner, it is possible to give a percentage discount.
    * Multiple payment options: Daily, Weekly, Monthly.
  * Based on the data stored in the database, the user can perform the following operations in the client application:
    * Based on the license plate or card number entered in the input field, the itemized parking list is displayed.
    * The user can export the list to JSON format, which will be saved in the root directory of the application.

Author: Sullivan008

Application.BusinessLogicLayer/Application.BusinessLogicLayer.csproj

@@ -0,0 +1,16 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net5.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="MediatR" Version="9.0.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Application.Core\Application.Core.csproj" />
+    <ProjectReference Include="..\Application.Infrastructure\Application.DataAccessLayer.csproj" />
+  </ItemGroup>
+
+</Project>

Application.BusinessLogicLayer/Interfaces/IBusinessLogicLayerMarker.cs

@@ -0,0 +1,5 @@
+namespace Application.BusinessLogicLayer.Interfaces
+{
+    public interface IBusinessLogicLayerMarker
+    { }
+}

Application.BusinessLogicLayer/MediatR/Abstractions/CommandBase.cs

@@ -0,0 +1,19 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Application.DataAccessLayer.Context;
+using MediatR;
+
+namespace Application.BusinessLogicLayer.MediatR.Abstractions
+{
+    public abstract class CommandBase<TCommand, TResult> : IRequestHandler<TCommand, TResult> where TCommand : IRequest<TResult>
+    {
+        protected readonly ParkingAppDbContext Context;
+
+        protected CommandBase(ParkingAppDbContext context)
+        {
+            Context = context;
+        }
+
+        public abstract Task<TResult> Handle(TCommand request, CancellationToken cancellationToken);
+    }
+}

Application.BusinessLogicLayer/MediatR/Abstractions/QueryBase.cs

@@ -0,0 +1,19 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Application.DataAccessLayer.Context;
+using MediatR;
+
+namespace Application.BusinessLogicLayer.MediatR.Abstractions
+{
+    public abstract class QueryBase<TQuery, TResult> : IRequestHandler<TQuery, TResult> where TQuery : IRequest<TResult>
+    {
+        protected ParkingAppReadonlyDbContext Context;
+
+        protected QueryBase(ParkingAppReadonlyDbContext context)
+        {
+            Context = context;
+        }
+
+        public abstract Task<TResult> Handle(TQuery request, CancellationToken cancellationToken);
+    }
+}

Application.BusinessLogicLayer/Modules/Parking/Commands/ExportParkingListCommand.cs

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+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Application.BusinessLogicLayer.MediatR.Abstractions;
+using Application.BusinessLogicLayer.Modules.Parking.Dtos;
+using Application.BusinessLogicLayer.Modules.Parking.RequestModels;
+using Application.Core.MediatR.Structs;
+using Application.Core.Services.Export.Interfaces;
+using Application.Core.Services.Export.Models;
+using Application.DataAccessLayer.Context;
+using MediatR;
+
+namespace Application.BusinessLogicLayer.Modules.Parking.Commands
+{
+    public class ExportParkingListCommand : IRequest<Result>
+    {
+        public IReadOnlyCollection<ExportParkingListItemDto> ExportList { get; }
+
+        public ExportParkingListCommand(ExportParkingListRequestModel model)
+        {
+            ExportList = model.ExportList.Select(x => new ExportParkingListItemDto
+            {
+                LicensePlateNumber = x.LicensePlateNumber,
+                StartDate = x.StartDate,
+                EndDate = x.EndDate,
+                IntervalInMinutes = x.IntervalInMinutes
+            }).ToList();
+        }
+    }
+
+    public class ExportParkingListCommandHandler : CommandBase<ExportParkingListCommand, Result>
+    {
+        private readonly IJsonExportService _jsonExportService;
+
+        public ExportParkingListCommandHandler(ParkingAppDbContext context, IJsonExportService jsonExportService) : base(context)
+        {
+            _jsonExportService = jsonExportService;
+        }
+
+        public override async Task<Result> Handle(ExportParkingListCommand request, CancellationToken cancellationToken)
+        {
+            ExportDataModel<ExportParkingListItemDto> exportDataModel = new()
+            {
+                DataSet = request.ExportList,
+                FileName = "export-result"
+            };
+
+            await _jsonExportService.ExportData(exportDataModel);
+
+            return Result.Success();
+        }
+    }
+}

Application.BusinessLogicLayer/Modules/Parking/Dtos/ExportParkingListItemDto.cs

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+using System;
+
+namespace Application.BusinessLogicLayer.Modules.Parking.Dtos
+{
+    public class ExportParkingListItemDto
+    {
+        public string LicensePlateNumber { get; init; }
+
+        public DateTime StartDate { get; init; }
+
+        public DateTime? EndDate { get; init; }
+
+        public double? IntervalInMinutes { get; init; }
+    }
+}

Application.BusinessLogicLayer/Modules/Parking/Queries/GetParkingListByCardNumberQuery.cs

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+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Application.BusinessLogicLayer.MediatR.Abstractions;
+using Application.BusinessLogicLayer.Modules.Parking.RequestModels;
+using Application.BusinessLogicLayer.Modules.Parking.ResponseModels;
+using Application.DataAccessLayer.Context;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+
+namespace Application.BusinessLogicLayer.Modules.Parking.Queries
+{
+    public class GetParkingListByCardNumberQuery : IRequest<ParkingListResponseModel>
+    {
+        public string CardNumber { get; }
+
+        public GetParkingListByCardNumberQuery(GetParkingListByCardNumberRequestModel model)
+        {
+            CardNumber = !string.IsNullOrWhiteSpace(model.CardNumber)
+                ? model.CardNumber.Trim()
+                : throw new ArgumentNullException(nameof(model.CardNumber), @"The value cannot be null!");
+        }
+    }
+
+    public class GetParkingListByCardNumberQueryHandler : QueryBase<GetParkingListByCardNumberQuery, ParkingListResponseModel>
+    {
+        public GetParkingListByCardNumberQueryHandler(ParkingAppReadonlyDbContext context) : base(context)
+        { }
+
+        public override async Task<ParkingListResponseModel> Handle(GetParkingListByCardNumberQuery request, CancellationToken cancellationToken)
+        {
+            ParkingListResponseModel result = new()
+            {
+                ParkingList = await Context.Cars.Include(x => x.Card)
+                                                .Include(x => x.LoggedParkingPeriods)
+                                                .Where(x => x.Card != null)
+                                                .Where(x => x.Card.Number.ToLower() == request.CardNumber.ToLower())
+                                                .SelectMany(x => x.LoggedParkingPeriods.Select(y => new ParkingListItemResponseModel
+                                                {
+                                                    LicensePlateNumber = x.LicensePlateNumber,
+                                                    StartDate = y.StartDate,
+                                                    EndDate = y.EndDate
+                                                }))
+                                                .ToListAsync(cancellationToken)
+            };
+
+            return result;
+        }
+    }
+}

Application.BusinessLogicLayer/Modules/Parking/Queries/GetParkingListByLicensePlateNumberQuery.cs

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+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Application.BusinessLogicLayer.MediatR.Abstractions;
+using Application.BusinessLogicLayer.Modules.Parking.RequestModels;
+using Application.BusinessLogicLayer.Modules.Parking.ResponseModels;
+using Application.DataAccessLayer.Context;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+
+namespace Application.BusinessLogicLayer.Modules.Parking.Queries
+{
+    public class GetParkingListByLicensePlateNumberQuery : IRequest<ParkingListResponseModel>
+    {
+        public string LicensePlateNumber { get; }
+
+        public GetParkingListByLicensePlateNumberQuery(GetParkingListByLicensePlateNumberRequestModel model)
+        {
+            LicensePlateNumber = !string.IsNullOrWhiteSpace(model.LicensePlateNumber)
+                ? model.LicensePlateNumber.Trim()
+                : throw new ArgumentNullException(nameof(model.LicensePlateNumber), @"The value cannot be null!");
+        }
+    }
+
+    public class GetParkingListByLicensePlateNumberQueryHandler : QueryBase<GetParkingListByLicensePlateNumberQuery, ParkingListResponseModel>
+    {
+        public GetParkingListByLicensePlateNumberQueryHandler(ParkingAppReadonlyDbContext context) : base(context)
+        { }
+
+        public override async Task<ParkingListResponseModel> Handle(GetParkingListByLicensePlateNumberQuery request, CancellationToken cancellationToken)
+        {
+            ParkingListResponseModel result = new()
+            {
+                ParkingList = await Context.Cars.Include(x => x.LoggedParkingPeriods)
+                                                .Where(x => x.Card == null)
+                                                .Where(x => x.LicensePlateNumber.ToLower() == request.LicensePlateNumber.ToLower())
+                                                .SelectMany(x => x.LoggedParkingPeriods.Select(y => new ParkingListItemResponseModel
+                                                {
+                                                    LicensePlateNumber = x.LicensePlateNumber,
+                                                    StartDate = y.StartDate,
+                                                    EndDate = y.EndDate
+                                                }))
+                                                .ToListAsync(cancellationToken)
+            };
+
+            return result;
+        }
+    }
+}

Application.BusinessLogicLayer/Modules/Parking/RequestModels/ExportParkingListItemRequestModel.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace Application.BusinessLogicLayer.Modules.Parking.RequestModels
+{
+    public class ExportParkingListItemRequestModel
+    {
+        public string LicensePlateNumber { get; init; }
+
+        public DateTime StartDate { get; init; }
+
+        public DateTime? EndDate { get; init; }
+
+        public double? IntervalInMinutes { get; init; }
+    }
+}

Application.BusinessLogicLayer/Modules/Parking/RequestModels/ExportParkingListRequestModel.cs

@@ -0,0 +1,9 @@
+using System.Collections.Generic;
+
+namespace Application.BusinessLogicLayer.Modules.Parking.RequestModels
+{
+    public class ExportParkingListRequestModel
+    {
+        public IReadOnlyCollection<ExportParkingListItemRequestModel> ExportList { get; init; }
+    }
+}