Finding Min & Max of a column for each identical value in another column

Question

I have a table in an EXCEL file as follows (I can read the excel file, thats not the problem here) -

+------------+-------+-------------+--------+-------+
|    Date    | RefNo | MasterName  | Value  | Type  |
+------------+-------+-------------+--------+-------+
| 01-01-2020 | 45    | ABC Pty Ltd | 123.45 | Sales |
| 01-01-2020 |  2    | XYZ Ltd     | 134.5  | Sales |
| 01-01-2020 | 46    | ABC Pty Ltd | 765    | Sales |
| 01-01-2020 | 47    | ABC Pty Ltd | 465.4  | Sales |
| 01-01-2020 | 3     | XYZ Ltd     | 468    | Sales |
| 01-01-2020 | S_1   | ABC Pty Ltd | 678    | Sales |
| 01-01-2020 | S_2   | XYZ Ltd     | 68     | Sales |
+------------+-------+-------------+--------+-------+

I use the following query to get the total amount against each 'Master' for each day (example table has only one day of sales) -

var query = data.GroupBy(row => new { row.Date, row.MasterName, row.Type })
    .Select(grp => new MasterAccount
    {
        Date = grp.Key.Date,
        Name = grp.Key.MasterName,
        Type = grp.Key.Type,
        Amount = grp.Sum(c => c.Value)
        MinRef = // Get minimum ref no. (type: int)
        MaxRef = // Get maximum ref no. (type: int)
    });

Note: As you can see, right now my code doesn't get the RefNo column when performing the 'GroupBy' cause if I do that, then it would create a new MasterAccount against each RefNo. And I dont want that.

I want to get the MinRef and MaxRef against each master . So in case of ' ABC Pty Ltd ' that would be 45 & 47 respectively, while ignoring the string ' S_1 '. Perhaps use TryParse to make sure that it isn't a string that cannot be converted into an int.

But I am not sure how to implement it within this code.

Answer 1

Define function which converts string to int? (null when converstion is not possible)

    private int? StrToInt(string s)
    {
        int i;
        if (int.TryParse(s, out i))
            return i;
        else
            return null;
    }

and then use it in the LINQ expression:

    MinRef = grp.Min(i => StrToInt(i.RefNo).GetValueOrDefault(0),
    MaxRef = grp.Max(i => StrToInt(i.RefNo).GetValueOrDefault(0)