C# - Parsing partial dates in different formats

Question

Hi there.
For use in a search method i would like to parse partial dates in different formats. I want to enable the user to search for day and month or month and year or also day and month and year.

But the more problematic thing is that i want do this in all possible date formats depending on the country, the user is in. It's a ASP.NET page and i can use the CultureInfo and therefore also the CultureInfo.DateTimeFormat.

Do you have any idea, how to do something like that? I think it would be great that a british person could search 16/05, while an american could enter 05/16 or a german could use 16.05 to find a result from the 16th of may.

I think it could be possible to use the DateTimeFormat.ShortDatePattern. But how could i use it to get day, month and year out of them?

I think of a use like

public void GetDateParts(string SearchStr, out int? day, out int? month, out int? year)

Thanks to anyone who can help me with this.

Answer 1

You can define a number of input formats and then impose one of them(based on info about the user) in your forms. Something like:

"Enter date(DD-MM):_ - _" for british

"Enter date(MM-DD):_ - _" for american

etc...

Answer 2

Like most of you mentioned, i think i will choose a method with a datepicker or dropdowns. But for those who are interested in another solution:

I thought about the different formats for a while and found that they are very similar in most cases. So i wrote a method that returns the best matching version of more often used patterns. So 'd.m.y.' -> 'd.m.y' or 'd/m y' -> 'd/m/y'.

public static string SimplifyDateFormat(DateTimeFormatInfo DTFI)
{
    StringBuilder SB = new StringBuilder(DTFI.ShortDatePattern.ToLower());

    SB.Replace("m y", "m/y").Replace(" 'г.'", "").Replace(" ", "").Replace("dd", "d")
    .Replace("mm", "m").Replace("yyyy", "y").Replace("yy", "y");

    if (SB[SB.Length - 1] == '.') SB.Remove(SB.Length - 1, 1);
    return SB.ToString();
}

This reduces the amount of possible formats from 26 to these 8:

• d/m/y
• d.m.y
• d-m-y
• y/m/d
• y.m.d
• y-m-d
• m/d/y
• m.d.y

These are only 3 different formats for parsing via regex if you use [\/.-] for the seperators.

P.S. Still doesn't fix the problem with partial dates. But search with full date for all cultures is possible.