C#

public bool TryGetCategory(string value, out string category)
{
    category = null;
    if (this.ContainsValue(value))
    {
        // Iterating through the key value pair to look for it's key
        foreach (KeyValuePair<string, string> pair in this)
        {
            if (pair.Value == value)
            {
                // We found a match. So assigning category
                category = pair.Key;
                return true;
            }
        }
    }
    return false;
}

d@nish wrote:

DictionaryEntry class

N a v a n e e t h wrote:

It's a structure, not a class

d@nish wrote:

There is method GetKeyForItem in KeyedCollectionClass

N a v a n e e t h wrote:

Do you mean putting another dictionary instance which is not visible to outside of class.

N a v a n e e t h wrote:

Will it be an performance overhead if collection is big ?

Guffa wrote:

as a dictionary uses about 20 bytes

[StructLayout(LayoutKind.Sequential)]
private struct Entry {
    public int hashCode;
    public int next;
    public TKey key;
    public TValue value;
}

S. Senthil Kumar wrote:

have two dictionaries, one keyed on your key and one keyed on your value.

S. Senthil Kumar wrote:

you could simply pack the key along with the value, internally (i.e Dictionary> [Wink] . That way, when you iterate through values and find a value, you can get the associated key right away.