How to map to a Dictionary object from database results using Dapper Dot Net?

If I have a simple query such as:

string sql = "SELECT UniqueString, ID  FROM Table";

and I want to map it to a dictionary object such as:

Dictionary<string, int> myDictionary = new Dictionary<string, int>();      

How would I do this with Dapper?

I assume it is something like:

myDictionary = conn.Query<string, int>(sql, new {  }).ToDictionary();

But can't figure out the proper syntax.