.net: Adding dictionary item - check if it exists or allow exception?

user_112194 0
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I'm adding items to a StringDictionary and it's possible that a duplicate key will come up. This will of course throw an exception.

If the chance of duplicates is very low (ie it will rarely happen), am I better off using a Try Catch block and leaving it unhandled, or should I always do a .ContainsKey check before adding each entry?

I'm assuming that if the likelihood of duplicate keys was high, then allowing exceptions would be a poor decision as they are expensive.

Thoughts?

Edit

I used reflector on the generic Dictionary and found the following for ContainsKey and TryGetValue, as both were mentioned below.

public bool TryGetValue(TKey key, out TValue value)
{
    int index = this.FindEntry(key);
    if (index >= 0)
    {
        value = this.entries[index].value;
        return true;
    }
    value = default(TValue);
    return false;
}

And

public bool ContainsKey(TKey key)
{
    return (this.FindEntry(key) >= 0);
}

Am I missing something, or is TryGetValue doing more work than ContainsKey ?

I appreciate the responses, and for my current purpose I'm going to go with doing a ContainsKey call as the collection will be small, and the code more readable.

dictionary .net
9 Answers

This issue is a lot simpler as of now for .NET Standard 2.1+ and .NET Core 2.0+. Just use the TryAdd method. It handles all the issues you have the most graceful way.

user_77614880
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