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c#linqexceptiondictionary
Moleman
Moleman

Reputation: 87

Catching exception in ToDictionary call

I have simple LINQ statement which splits a string and then throws the values into a dictionary. The problem is that rarely the dictionary already has an existing key of the same value so an exception is thrown and the the value of "dict" remains empty. 

dict = lines.Select(l => l.Split('|')).ToDictionary(d => d[0], d => d[1]);

Is there a way to modify the LINQ statement to check if the dictionary already has the key before inserting it or to catch the exception but continue writing the rest of the values into the dictionary? I tried putting a try block around the line and it catches the exception but results in no elements being added so the dictionary remains empty.

Upvotes: 4

Views: 2851

Answers (3)

Hamlet Hakobyan
Hamlet Hakobyan

Reputation: 33381

If you need dictionary which holds one value per key you can use this:

var dict1 = lines
          .Select(l => l.Split('|'))
          .GroupBy(s => s[0])
          .ToDictionary(d => d.Key, d => d.First()[1]);

or you can use this, if you want Dictionary<string,IEnumerable<string>> which holds keys and corresponding values as IEnumerable<string>

var dict2 = lines
           .Select(l => l.Split('|'))
           .GroupBy(s => s[0])
           .ToDictionary(d => d.Key, d => d.Select(r => r[1]));

Upvotes: 0

Joachim Isaksson
Joachim Isaksson

Reputation: 180917

You could always just use GroupBy to create a group per key, and just pick the first value per key to the dictionary;

var dict = lines.Select(x => x.Split('|'))
                .GroupBy(x => x[0], x => x[1])
                .ToDictionary(x => x.Key, x => x.First());

Upvotes: 3

Oded
Oded

Reputation: 499002

Do not use ToDictionary but a regular foreach and test the keys.

Break the query from the conversion to a dictionary.

var splits = lines.Select(l => l.Split('|'));

var dict = new Dictionary<string,string>();
foreach(var item in splits)
{
   if(!dict.ContainsKey(item[0]))
       dict.Add(item[0], item[1]);
}

Upvotes: 5

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