Linq join - is there a better way?

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Hi,

I have to parse a date string. the year, month and day can all be in various formats (year in "yy" or "yyyy").

To get an array of valid formats, I have each date-part in a separate array. I join all of these together using the Join(this Enumerable source) linq extension. Code below:

C#

private string[] years = { "yy", "yyy" };
private string[] months = { "M", "MM" };
private string[] days = { "d", "dd" };

string[] formats
{
    get
    {
        return years.Join(
                months,
                y => 1,
                m => 1,
                (y, m) => new {y, m}
            ).Join(
                days,
                n => 1,
                d => 1,
                (n, d) => string.Join("/", n.y, n.m, d)
            ).ToArray();
    }
}

I'm sure you can see the bit I don't like. Joining tables on 1=1, bleh!

I prefer extension syntax to linq syntax, so I won't be using that, but it's popularity makes google searches all the more difficult.

So: How SHOULD I be joining these arrays?

Thanks ^_^
Andy

Posted 19-May-15 4:54am

Andy Lanng

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Richard Deeming · Accepted Answer · 2015-05-19T06:58:00

SelectMany[^] would probably be a better fit:

C#

return years
    .SelectMany(y => months, (y, m) => new { y, m })
    .SelectMany(ym => days, (ym, d) => ym.y + "/" + ym.m + "/" + d })
    .ToArray();

The equivalent query syntax would be:

C#

var query = from y in years
            from m in months
            from d in days
            select y + "/" + m + "/" + d;

return query.ToArray();