Check if KeyValuePair exists with LINQ's FirstOrDefault

Question

I have a dictionary of type

Dictionary

I want to return the first instance where a condition is met using

var         


        

Answer 1

I suggest you change it in this way:

var query = m_AvailableDict.Where(p => p.Value == 0).Take(1).ToList();

You can then see whether the list is empty or not, and take the first value if it's not, e.g.

if (query.Count == 0)
{
    // Take action accordingly
}
else
{
    Guid key = query[0].Key;
    // Use the key
}

Note that there's no real concept of a "first" entry in a dictionary - the order in which it's iterated is not well-defined. If you want to get the key/value pair which was first entered with that value, you'll need an order-preserving dictionary of some kind.

(This is assuming you actually want to know the key - if you're just after an existence check, Marc's solution is the most appropriate.)