Returning the existence of a key in a dict by searching key substring

Question

I have a dictionary of string people (key) and string addresses (value). I want to have an if statement that returns true if any key in my dictionary contains the substring 'anders'. Is there any way to do this? I have tried dict.ContainsKey("anders") but that just returns true if any key is explicitly named 'anders'. I would like it to return true even if the key is anderson or andersen. I know this is a pretty strange case but i need it for a purpose.

Thanks

M.Babcock · Answer 1 · 2012-03-12T18:27:59.090

6

You'll have to iterate over the collection and check each one. The LINQ Any method makes this fairly simple:

dict.Keys.Any(k => k.Contains("anders"))

edited Mar 12 '12 at 18:27

answered Mar 12 '12 at 18:21

M.Babcock

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score 2 · Answer 2 · edited May 23 '17 at 12:33

2

Everyone has already pointed out the obvious (and correct) Any method, but one note: Using String.Contains as the predicate will only return true if the case of the substring is also correct. To do a case-insensitive search, use a simple Regex:

dict.Keys.Any(x => Regex.IsMatch(x, "(?i)anders"));

Or use IndexOf with the StringComparison argument (as in Case insensitive 'Contains(string)'):

dict.Keys.Any(x => x.IndexOf("anders", StringComparison.InvariantCultureIgnoreCase) >= 0);

edited May 23 '17 at 12:33

Community

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answered Mar 12 '12 at 18:35

Joshua Honig

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@M.Babcock I had already updated my answer when I saw your comment :) – Joshua Honig Mar 12 '12 at 18:41
The string comparison is less important than the iteration, in my opinion, but you make an excellent point. – Randolpho Mar 12 '12 at 19:33

score 1 · Answer 3 · answered Mar 12 '12 at 18:21

1

var pair = dict.FirstOrDefault(kvp => kvp.Key.Contains("anders"));

answered Mar 12 '12 at 18:21

SLaks

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score 1 · Accepted Answer · answered Mar 12 '12 at 18:23

There is no "wildcard search" for dictionary keys. In order to do this type of search, you are going to lose the O(constant) search that a dictionary gives you.

You'll have to iterate over the keys of the dictionary and look for those that contain the substring you require. Note that this will be an O(n*X) iteration, where n is the number of keys and X is the average size of your key string.

There's a nifty one-liner that will help:

bool containsKey = myDictionary.Keys.Any(x => x.Contains("mySubString"));

But it's a heavy operation.

score 0 · Answer 5 · answered Mar 12 '12 at 18:21

0

if(dict.Keys.Any(k=>k.Contains("anders")))
{
    //do stuff
}

answered Mar 12 '12 at 18:21

Călin Darie

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score 0 · Answer 6 · answered Mar 12 '12 at 18:23

You can iterate the keys of the dictionary and check each if it contains the string:

bool found = false;
foreach (string key in dict.Keys)
{
    if (key.Contains("anders"))
    {
        found = true;
        break;
    }
}

or using LINQ:

bool found = dict.Keys.Any(key => key.Contains("anders"));

Returning the existence of a key in a dict by searching key substring

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