How can I reduce this method without using the If condition?

Question

I'm trying to use the entity framework to filter my GET method... Using the if the condition it's working

 public async Task<List<TimeEntryViewModel>> Get(TimeEntryFilter filter)
        {
            var result = await _readRepository
                .FindByCondition(x => x.IsApproved == true)
                .Include(x => x.Task)
                .Include(x => x.Account)
                .Select(x => new TimeEntryViewModel
                {
                    AccountName = x.Account.Name,
                    Date = x.Date,
                    StartTime = x.StartTime,
                    FinishTime = x.FinishTime,
                    InternalId = x.InternalId,
                    TaskId = x.TaskId,
                    TaskName = x.Task.Name,
                    CreatedBy = x.CreatedBy,
                    CustomerName = x.Task.Project.ServiceOrder.Customer.Name
                }).ToListAsync().ConfigureAwait(false);

            if  (filter.AccountName != null || 
                (filter.StartDate.HasValue && filter.FinishDate.HasValue && (filter.StartDate <= filter.FinishDate)) ||
                (filter.TaskName != null) ||
                (filter.CustomerName != null) ||
                (filter.InternalId != null))
                result = result.Where(x => 
                                        (x.AccountName.ToString().Contains(filter.AccountName)) &&
                                        (x.Date >= filter.StartDate && x.Date <= filter.FinishDate) &&
                                        (x.CustomerName.ToString().Contains(filter.CustomerName)) &&
                                        (x.TaskName.ToString().Contains(filter.TaskName)) &&
                                        (x.InternalId.ToString().Contains(filter.InternalId.ToString()))).ToList();

            return result;
        }

But I imagine that there is a way to improve this method without using if

I'd had already tried to do that (Just filter account name to show) But returned Internal Server Error

var result = await _readRepository
                .FindByCondition(x => x.IsApproved == true)
                .Where(x => string.IsNullOrEmpty(filter.AccountName) || x.Account.Name.ToString().Contains(filter.AccountName))
                .Include(x => x.Task)
                .Include(x => x.Account)
                .Select(x => new TimeEntryViewModel
                {
                    Id = x.Id,
                    AccountName = x.Account.Name,
                    Date = x.Date,
                    Description = x.Description,
                    StartTime = x.StartTime,
                    FinishTime = x.FinishTime,
                    InternalId = x.InternalId,
                    OnSite = x.OnSite,
                    IsApproved = x.IsApproved,
                    IsBillable = x.IsBillable,
                    TaskId = x.TaskId,
                    TaskName = x.Task.Name,
                    CreatedBy = x.CreatedBy,
                    CustomerName = x.Task.Project.ServiceOrder.Customer.Name
                }).ToListAsync().ConfigureAwait(false);

Okay Guys EDIT1: In my second sample, using InternalId instead of Account.Name

.Where(x => (string.IsNullOrEmpty(filter.InternalId.ToString())) || x.InternalId.ToString().Contains(filter.InternalId.ToString()))

it worked.... I believe that I'm having trouble to work with something that is a foreign key in my table...

score 1 · Answer 1 · answered Dec 17 '19 at 14:51

1

There is a very interesting way to mass multiple bool values (contains or not etc) with only one value. It's called bit bitwise operations. Here: Most common C# bitwise operations on enums you can find different approachs to this "technique".

answered Dec 17 '19 at 14:51

Iavor Orlyov

512
1
4
15

Christos · Answer 2 · 2019-12-17T14:57:44.073

It returned null because you don't check if Account property is null.

 AccountName = x.Account.Name

So the above will throw a Null Reference Exception.

A way to avoid this, it is to use the null conditional operator:

AccountName = x.Account?.Name

You can follow the same approach also for properties like:

Task.Name
Task.Project.ServiceOrder.Customer.Name

And access them safely, by using the same operator, like below:

Task?.Name
Task?.Project?.ServiceOrder?.Customer?.Name

Based on the above you can follow the way you have already followed for AccountName property, but you have also at the same time to use the null conditional operator.

If I change to the second way, I got the error An expression tree lambda may not contain a null propagating operator. — Ravel Sbrissa Okada, Dec 17 '19 at 15:59

score 1 · Answer 3 · answered Dec 17 '19 at 14:58

1

It looks like you need && operator:

.Where(x => string.IsNullOrEmpty(filter?.AccountName) 
    && x?.Account?.Name.ToString().Contains(filter.AccountName))

because when you use || operator, then you can get NullReferenceException in the second part of your expression in Where:

x?.Account?.Name.ToString().Contains(filter.AccountName))

answered Dec 17 '19 at 14:58

StepUp

36,391
15
88
148

But in this way, I won't get the right SQL expression – Ravel Sbrissa Okada Dec 17 '19 at 15:55

score 0 · Accepted Answer · answered Dec 17 '19 at 16:50

Okay, apparently, my problem was .Where(x => string.IsNullOrEmpty(filter.AccountName) || x.Account.Name.ToString().Contains(filter.AccountName)) after x.Account.Name I can't use ToString()... I don't know exactly why, but now works without the if condition

public async Task<List<TimeEntryViewModel>> GetApproved(TimeEntryFilter filter)
        {
            var result = await _readRepository
                .FindByCondition(x => x.IsApproved == true)
                .Include(x => x.Task)
                .Include(x => x.Account)
                .Where(x => 
                            (string.IsNullOrEmpty(filter.InternalId.ToString()) || x.InternalId.ToString().Contains(filter.InternalId.ToString())) &&
                            (string.IsNullOrEmpty(filter.AccountName) || x.Account.Name.Contains(filter.AccountName)) && 
                            (string.IsNullOrEmpty(filter.CustomerName) || x.Task.Project.ServiceOrder.Customer.Name.Contains(filter.CustomerName)) &&
                            (string.IsNullOrEmpty(filter.TaskName) || x.Task.Name.Contains(filter.TaskName)))
                .Select(x => new TimeEntryViewModel
                {
                    Id = x.Id,
                    AccountName = x.Account.Name,
                    Date = x.Date,
                    Description = x.Description,
                    StartTime = x.StartTime,
                    FinishTime = x.FinishTime,
                    InternalId = x.InternalId,
                    OnSite = x.OnSite,
                    IsApproved = x.IsApproved,
                    IsBillable = x.IsBillable,
                    TaskId = x.TaskId,
                    TaskName = x.Task.Name,
                    CreatedBy = x.CreatedBy,
                    CustomerName = x.Task.Project.ServiceOrder.Customer.Name
                }).ToListAsync().ConfigureAwait(false);

            return result;
        }

If anyone knows why it's working, I'll be thankful

How can I reduce this method without using the If condition?

4 Answers4