Add validation to prevent updates with duplicate national codes

src/CMSMicroservice.Application/UserCQ/Commands/UpdateUser/UpdateUserCommandHandler.cs

@@ -1,5 +1,7 @@
 using CMSMicroservice.Domain.Events;
+
 namespace CMSMicroservice.Application.UserCQ.Commands.UpdateUser;
+
 public class UpdateUserCommandHandler : IRequestHandler<UpdateUserCommand, Unit>
 {
     private readonly IApplicationDbContext _context;
@@ -11,16 +13,19 @@ public class UpdateUserCommandHandler : IRequestHandler<UpdateUserCommand, Unit>
 
     public async Task<Unit> Handle(UpdateUserCommand request, CancellationToken cancellationToken)
     {
-        var entity = await _context.Users
-            .FirstOrDefaultAsync(x => x.Id == request.Id, cancellationToken) ?? throw new NotFoundException(nameof(User), request.Id);
-        if (!string.IsNullOrWhiteSpace(request.NationalCode) && entity.NationalCode == request.NationalCode)
+        if (!string.IsNullOrWhiteSpace(request.NationalCode) &&
+            _context.Users.Any(a => a.NationalCode == request.NationalCode))
         {
             throw new Exception("کد ملی تکراری است");
         }
+
+        var entity = await _context.Users
+                         .FirstOrDefaultAsync(x => x.Id == request.Id, cancellationToken) ??
+                     throw new NotFoundException(nameof(User), request.Id);
         request.Adapt(entity);
         _context.Users.Update(entity);
         entity.AddDomainEvent(new UpdateUserEvent(entity));
         await _context.SaveChangesAsync(cancellationToken);
         return Unit.Value;
     }
-}
+}