Question

I’m converting a comma separated list of strings into a dictionary using C# in ASP.NET (by omitting any duplicates):

string str = "1,2, 4, 2, 4, item 3,item2, item 3"; //Just a random string for the sake of this example

and I was wondering which method is more efficient?

1 – Using try/catch block:

Dictionary<string, string> dic = new Dictionary<string, string>();

string[] strs = str.Split(',');
foreach (string s in strs)
{
    if (!string.IsNullOrWhiteSpace(s))
    {
        try
        {
            string s2 = s.Trim();
            dic.Add(s2, s2);
        }
        catch
        {
        }
    }
}

2 – Or using ContainsKey() method:

string[] strs = str.Split(',');
foreach (string s in strs)
{
    if (!string.IsNullOrWhiteSpace(s))
    {
        string s2 = s.Trim();
        if (!dic.ContainsKey(s2))
            dic.Add(s2, s2);
    }
}

EDIT. Thank you everyone who participated!

A very interesting find. If you look at the answer provided by dtb below, he proposed two methods of using hashSet. I’ll dub them over here:

Method 1:

var hashSet = new HashSet<string>(from s in str.Split(',')
                           where !string.IsNullOrWhiteSpace(s)
                           select s.Trim()); 

Method 2:

var hashSet = new HashSet<string>();
foreach (string s in str.Split(','))
{
     if (!string.IsNullOrWhiteSpace(s))
     {
         hashSet.Add(s.Trim());
     }
}

I asked him which method is faster performance-wise, and interestingly enough, method 2 is faster. Here’s the timing done using the Stopwatch class by running each method in a Release build for 1,000,000 times in a loop:

Method 1: 1,440 ms average
Method 2: 1,124 ms average

Answer 1

If you need a set and not a dictionary, I recommend you use the HashSet<T> Class:

HashSet<T> Class

Represents a set of values.

A set is a collection that contains no duplicate elements, and whose elements are in no particular order.

---

var hashSet = new HashSet<string>(from s in str.Split(',')
                                  where !string.IsNullOrWhiteSpace(s)
                                  select s.Trim());

or equally

var hashSet = new HashSet<string>();
foreach (string s in str.Split(','))
{
    if (!string.IsNullOrWhiteSpace(s))
    {
        hashSet.Add(s.Trim());
    }
}