Pull a Dictionary Entry using Date only

August 4, 2022

I have a dictionary of type Dictionary<DateTime, Cars>

In the sample dictionary below, is it possible to pick out the value for june 2nd using the date only as the Key?

 [0]: {[{31-May-2022 6:12:30 AM}, {Cars}]}
 [1]: {[{01-Jun-2022 8:52:10 AM}, {Cars}]}
 [2]: {[{02-Jun-2022 6:19:17 AM}, {Cars}]}
 [3]: {[{03-Jun-2022 6:27:39 AM}, {Cars}]}
 [4]: {[{04-Jun-2022 6:47:00 AM}, {Cars}]}

thanks!

>Solution :

If you already have a Dictionary that was created without that definition of "equality", then the best you can do is iterate through the keys.

You could alternatively create the dictionary with a IEqualityComparer<DateTime> class that defines "equality" as looking at the date only:

class DateEqualityComparer : IEqualityComparer<DateTime>
{
    public bool Equals(DateTime d1, DateTime d2)
    {
        if(d1.Date == d2.Date)
            return true;
        else
            return false;
    }

    public int GetHashCode(DateTime d)
    {
        return d.Date.GetHashCode();
    }
}

Note that:

This class would need to be used to create the dictionary; it could not be used after the fact
It would prevent the dictionary from having multiple DateTime key values with the same date; Adding a key with the same date but a different time would create a collision