Get Dictionary key by value

[=?Utf-8?B?THVpZ2k=?=]

Hi all,
having a dictionary of <int, string(C# 2.0) is there a way to retrieve the
key for a specific value (of type string)?
Obviously I populate the Dictionary with not duplicated strings.

Thanks a lot.
--
Luigi

[Marc Gravell]

Re: Get Dictionary key by value

Probably the easiest option here is to loop over the pairs;

public static int? FindKey(
this IDictionary<int , stringlookup,
string value)
{
foreach (var pair in lookup)
{
if (pair.Value == value)
return pair.Key;
}
return null;
}

Which you can then call via:

Dictionary<int, stringlookup = new Dictionary<int,
string>(); // etc
int? value = lookup.FindKey( "abc");
if (value.HasValue )
{
Console.WriteLi ne("Found it: " + value.Value);
}

Marc

[Mark Rae [MVP]]

Re: Get Dictionary key by value

"Luigi" <ciupazNoSpamGr azie@inwind.itw rote in message
news:585E7C1B-FD1C-4641-AE1F-D6F3A84DA3F7@mi crosoft.com...

having a dictionary of <int, string(C# 2.0) is there a way to retrieve
the
key for a specific value (of type string)?

http://www.google.co.uk/search?hl=en&rlz=1T4GZEZ_en-GBGB252GB252&q=%22C%23%22+Dictionary+find+key+by+value&meta=

--
Mark Rae
ASP.NET MVP

http://www.markrae.net

[Jon Skeet [C# MVP]]

Re: Get Dictionary key by value

Luigi <ciupazNoSpamGr azie@inwind.itw rote:

having a dictionary of <int, string(C# 2.0) is there a way to retrieve the
key for a specific value (of type string)?
Obviously I populate the Dictionary with not duplicated strings.

No - a dictionary is a one way mapping. If you want to be able to map
both ways, you need two dictionaries.

--
Jon Skeet - <skeet@pobox.co m>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon.skeet
C# in Depth: http://csharpindepth.com

[OD]

Re: Get Dictionary key by value

Hi all,

having a dictionary of <int, string(C# 2.0) is there a way to retrieve the
key for a specific value (of type string)?
Obviously I populate the Dictionary with not duplicated strings.
>
Thanks a lot.

dictionnaries are "one way". you'll have to iterate or use a second
dictionnary.

You said you're using C# 2.0, so just to show you what C#3.0 can bring,
you can simplify your code using a Linq query like this (case
insensitive search of string "two" in a dictionnary "dic"
dictionnary<int ,string>) :

var key = (from k in dic where string.Compare( k.Value, "two", true) ==
0 select k.Key).FirstOrD efault();
Console.WriteLi ne(key);

--


OD___

https://www.e-naxos.com