(B) Apply result pattern on CQRS

Clinics.Backend/Application/Abstractions/CQRS/Commands/ICommand.cs

-using MediatR;
+using Domain.Shared;
+using MediatR;
 
 namespace Application.Abstractions.CQRS.Commands;
 
 // No response
-public interface ICommand : IRequest
+public interface ICommand : IRequest<Result>
 {
 }
 
 // With response
-public interface ICommand<TResponse> : IRequest<TResponse>
+public interface ICommand<TResponse> : IRequest<Result<TResponse>>
 {
 }

Clinics.Backend/Application/Abstractions/CQRS/Commands/ICommandHandler.cs

-using MediatR;
+using Domain.Shared;
+using MediatR;
 
 namespace Application.Abstractions.CQRS.Commands;
 
 // No response
-public interface ICommandHandler<TCommand> : IRequestHandler<TCommand>
+public interface ICommandHandler<TCommand> : IRequestHandler<TCommand, Result>
     where TCommand : ICommand
 {
 }
 
 // With response
 public interface ICommandHandler<TCommand, TResponse>
-    : IRequestHandler<TCommand, TResponse>
+    : IRequestHandler<TCommand, Result<TResponse>>
     where TCommand : ICommand<TResponse>
 {
 }
\ No newline at end of file

Clinics.Backend/Application/Abstractions/CQRS/Queries/IQuery.cs

-using MediatR;
+using Domain.Shared;
+using MediatR;
 
 namespace Application.Abstractions.CQRS.Queries;
 
-public interface IQuery<TResponse> : IRequest<TResponse>
+public interface IQuery<TResponse> : IRequest<Result<TResponse>>
 {
 }

Clinics.Backend/Application/Abstractions/CQRS/Queries/IQueryHandler.cs

-using MediatR;
+using Domain.Shared;
+using MediatR;
 
 namespace Application.Abstractions.CQRS.Queries;
 
 public interface IQueryHandler<TQuery, TResponse>
-    : IRequestHandler<TQuery, TResponse>
+    : IRequestHandler<TQuery, Result<TResponse>>
     where TQuery : IQuery<TResponse>
 {
 }

Clinics.Backend/Application/Employees/Commands/Create/CreateEmployeeCommandHandler.cs

 using Application.Abstractions.CQRS.Commands;
 using Domain.Entities.People.Employees;
 using Domain.Repositories;
+using Domain.Shared;
 using Domain.UnitOfWork;
 
 namespace Application.Employees.Commands.Create;
@@ -17,39 +18,35 @@ public class CreateEmployeeCommandHandler : ICommandHandler<CreateEmployeeComman
     }
     #endregion
 
-    public async Task Handle(CreateEmployeeCommand request, CancellationToken cancellationToken)
+    public async Task<Result> Handle(CreateEmployeeCommand request, CancellationToken cancellationToken)
     {
-        #region Create new employee
-        Employee employee;
-        try
-        {
-            employee = Employee.Create(
-                request.FirstName, request.MiddleName, request.LastName, // Personal info
+        Result<Employee> employeeResult =
+            Employee
+            .Create(
+                request.FirstName, request.MiddleName, request.LastName,
 
-                request.DateOfBirth, request.Gender, // Patient info
+                request.DateOfBirth, request.Gender, request.SerialNumber, request.CenterStatus, false,
 
-                request.SerialNumber, request.CenterStatus, false, // Employee info
+                request.StartDate, request.AcademicQualification, request.WorkPhone, request.Location, request.Specialization,
+                request.JobStatus
+                );
+        if (employeeResult.IsFailure)
+            return Result.Failure(employeeResult.Error);
 
-                request.StartDate, request.AcademicQualification, request.WorkPhone, // additional
-                request.Location, request.Specialization, request.JobStatus);
-        }
-        catch (Exception)
-        {
-            throw;
-        }
-        #endregion
-
-        #region Add to DB
         try
         {
-            _employeesRepository.Create(employee);
+            _employeesRepository.Create(employeeResult.Value);
             await _unitOfWork.SaveChangesAsync();
         }
-        catch (Exception)
+        catch (Exception exp)
         {
-            throw;
+            // For debugging
+            //return Result.Failure(new Error("Persistence.UnableToSaveTransaction", exp.Message));
+
+            // For deployment
+            return Result.Failure(Domain.Errors.PersistenceErrors.UnableToCompleteTransaction);
         }
-        #endregion
 
+        return Result.Success();
     }
 }

Clinics.Backend/Domain/Errors/PersistenceErrors.cs

+using Domain.Shared;
+
+namespace Domain.Errors;
+
+public static class PersistenceErrors
+{
+    public static Error UnableToCompleteTransaction =>
+        new("Persistence.UnableToCompleteTransaction", "حدثت مشكلة عند الاتصال مع قاعدة البيانات");
+}

Clinics.Backend/Persistence/UnitOfWork/UnitOfWork.cs

@@ -21,7 +21,7 @@ public class UnitOfWork : IUnitOfWork
         catch (Exception)
         {
             // TODO: Log errors using ILogger
-            //throw;
+            throw;
         }
     }
 }

Clinics.Backend/Presentation/Controllers/EmployeesController.cs

@@ -20,7 +20,9 @@ public class EmployeesController : ControllerBase
     [HttpPost]
     public async Task<IActionResult> Create(CreateEmployeeCommand command)
     {
-        await _sender.Send(command);
-        return Ok();
+        var result = await _sender.Send(command);
+        if (result.IsSuccess)
+            return Created();
+        else return BadRequest(result.Error.Message);
     }
 }