（代码完成）组合两个任务列表（表格）以显示总结果

Question

Today I'm trying to achieve something that I'm having difficulties with the code-completion. I'm trying to combine two tasks (which are from different types).

Before reaching here, I've tried several scenarios.... Using WhenAll to combine Tasks (which I cannot do this since both tasks are different).

The last part of the code (last 3 lines) are not correct and I'll ask if someone can take a look on this:) (Also if the method arguments are okay for this matter). All I want is to return the list of the total rows combined by the two tasks.

Thanks in advance! (Code is below)

public async Task<(ApplyPerfectMatches, ApplyNonPerfectMatches)>
                GetMatchesAsync(string currentUser)
            {
                // Perfect Matches
                var listPerfectMatches = _context.ApplyPerfectMatches
                    .Where(x => x.IdEmailInvestor == currentUser)
                     // Use AsNoTracking to disable EF change tracking
                     // Use ToListAsync to avoid blocking a thread
                     .AsNoTracking().ToListAsync();
    
                // Determine Total matches vs. Limit matches per user
                int totalMatches = _context.ApplyPerfectMatches.Where(x => x.IdEmailInvestor == currentUser).Count();
                int totalMatchesBy10 = totalMatches / 10;
    
                // n(n-1)/2 + 2 (n = 1...n+1 => 2, 3, 5, 8, 12, 17, 23, 30...)
                int limitMatches = totalMatches < 10 ? 3 : (totalMatchesBy10 * (totalMatchesBy10 - 1) / 2) + 2;
    
                var submitDate = _context.ApplyPerfectMatches
                    .Where(x => x.IdEmailInvestor == currentUser)
                    .OrderByDescending(x => x.DtSubmitInvestor)
                    .Select(x => x.DtSubmitInvestor)
                    .FirstOrDefault();
    
                int days = (DateTime.Now - submitDate).Days;
    
                if (days > 3)
                {
                    listPerfectMatches = _context.ApplyPerfectMatches
                    .Where(x => x.IdEmailInvestor == currentUser)
                    .Take(limitMatches)
                     // Use AsNoTracking to disable EF change tracking
                     // Use ToListAsync to avoid blocking a thread
                     .AsNoTracking().ToListAsync();
                }
                else
                {
                    listPerfectMatches = _context.ApplyPerfectMatches
                    .Where(x => x.IdEmailInvestor == currentUser)
                    .Take(3)
                     // Use AsNoTracking to disable EF change tracking
                     // Use ToListAsync to avoid blocking a thread
                     .AsNoTracking().ToListAsync();
                }            
    
                // Total Matches (Perfect + Non-Perfect Matches)
                var listNonPerfectMatches = _context.ApplyNonPerfectMatches
                    .Where(x => x.IdEmailInvestor == currentUser)
                     // Use AsNoTracking to disable EF change tracking
                     // Use ToListAsync to avoid blocking a thread
                     .AsNoTracking().ToListAsync();
    
    
                var finalResult = listPerfectMatches.Result.Concat(listNonPerfectMatches.Result).ToList();           
    
                //await Task.WhenAll(tasks);
                //return tasks.SelectMany(t => t.Result).ToList();
            }

Update (I don't mind the negative votes but if someone needs help, that same person might be confused with the problem...):

result = await _context.ApplyTotalMatches
                // Only get entries for the current logged in user
                .Where(x => x.IdEmailInvestor == currentUser && x.UnionSetOrder == 1)
                .Take(limitMatches)
                .Concat(_context.ApplyTotalMatches
                .Where(x => x.IdEmailInvestor == currentUser && x.UnionSetOrder == 2))
                // Use AsNoTracking to disable EF change tracking
                // Use ToListAsync to avoid blocking a thread
                .AsNoTracking().ToListAsync();

Answer 1

You have to await a Task object. This "unwraps" the result:

public async (List<ApplyPerfectMatches> PerfectMatches, List<ApplyNonPerfectMatches> NonApplyPerfectMatches) GetMatchesAsync(string currentUser)
{
  List<ApplyPerfectMatches> listPerfectMatches = await _context.ApplyPerfectMatches
    .Where(x => x.IdEmailInvestor == currentUser)
    .Take(3)
    .AsNoTracking()
    .ToListAsync();

  List<ApplyNonPerfectMatches> listNonPerfectMatches = await _context.ApplyNonPerfectMatches
    .Where(x => x.IdEmailInvestor == currentUser)
    .AsNoTracking()
    .ToListAsync();

  return (listPerfectMatches, listNonPerfectMatches);   
}

async Task Run()
{
  (List<ApplyPerfectMatches> PerfectMatches, List<ApplyNonPerfectMatches> NonApplyPerfectMatches) result = await GetMatchesAsync("Admin");
}

Directly accessing Task.Result can cause a deadlock. QueryableExtensions.ToListAsync is an asynchronous method. Asynchronous methods always return a Task<T> or Task and must be awaited using await in order to execute asynchronously.

Answer 2

First, you need to define a new class:

public class GetMatchesResult {
   public string IdEmailInvestor { set; get; }
   public bool IsPerfectMatch { set; get; }
   ... rest of properties/columns go here
}

Since your method is defined as

async Task<(ApplyPerfectMatches, ApplyNonPerfectMatches)>

you need to change it to:

async Task<List<GetMatchesResult>> GetMatches

Now, you need to update the queries to:

 // Perfect Matches
 var listPerfectMatches = await _context.ApplyPerfectMatches
     .Where(x => x.IdEmailInvestor == currentUser)
     .Select(x => new GetMatchesResult {
         IdEmailInvestor = x.IdEmailInvestor,
         IsPerfectMatch = true,
         ... rest of properties go here
     })
     // Use ToListAsync to avoid blocking a thread
     .ToListAsync();
                     

You need to do the same with the listNonPerfectMatches, but set the IsPerfectMatch to false.

In the end, you can do:

return listPerfectMatches.Concat(listNonPerfectMatches);