Push records from one model array to another model array with conditions

Question

I have below two models:

TrackList:

public int id { get; set; }
public string name { get; set; }
public int apr_by { get; set; }
public int reg_by { get; set; }

TrackListMain:

public int id { get; set; }
public string name { get; set; }
public string status { get; set; }

Suppose I would get the below records from DB in the model array TrackList by executing:

var dbArray = await _SQLHelper.GetRecords<TrackList>("[TASKLIST]", parameters);

id	name	apr_by	reg_by
1	aaa	1	1
2	bbb	2	null
3	ccc	null	3
4	ddd	null	null

Now I need to push each record to the model array TrackListMain based on these conditions:

foreach dbArray => {
    if (`dbArray.apr_by` == null && `reg_by` == null), push to `TrackListMain` and update `status` field with `null`
    if `dbArray.apr_by` !=null, push to `TrackListMain` and update `status` field with `AB`
    if `dbArray.reg_by` !=null, push to `TrackListMain` and update `status` field with `RB`
}

And my resultant array IEnumerable<TrackListMain> mainArray should contain data with the below format:

id	name	status
1	aaa	AB
1	aaa	RB
2	bbb	AB
3	ccc	RB
4	ddd	null

Can you help me to achieve this in C# either by using LINQ?

Answer 1

For LINQ approach,

1. Filter data by conditions (3 sets) and decorate the output result.

2. Combine 3 set of data into one with .Union().

3. Order the result by Id.

List<TrackListMain> result = (dbArray.Where(x => x.Apr_By == null && x.Reg_By == null)
                                 .Select(x => new TrackListMain
                                         {
                                             Id = x.Id,
                                             Name = x.Name,
                                             Status = null
                                         })
                            )
                            .Union(dbArray.Where(x => x.Apr_By != null)
                                 .Select(x => new TrackListMain
                                         {
                                             Id = x.Id,
                                             Name = x.Name,
                                             Status = "AB"
                                         })
                            )
                            .Union(dbArray.Where(x => x.Reg_By != null)
                                 .Select(x => new TrackListMain
                                         {
                                             Id = x.Id,
                                             Name = x.Name,
                                             Status = "RB"
                                         })
                            )
                            .OrderBy(x => x.Id)
                            .ToList();

Demo @ .NET Fiddle