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);
    }
}