Some basics :
1) A dictionary or hashtable is a structure for storing information referenced by a key.
Dictionary<string,string> dic = new Dictionary<string,string>();
dic.Add("somestringkey","value associated with key");
dic["someotherkey"] = "another value for that key";
string val = dic["somestringkey"];
2) To create a keyvalue store in RaptorDB of type hash for storing strings up to 255 chars in a file named storage (with various extensions for indexes etc.).
RaptorDB.RaptorDB rap = RaptorDB.RaptorDB.Open("storage", 255, false, INDEXTYPE.HASH);
rap.Set("somestringkey","value associated with key");
string val = "";
if(rap.Get("somestringkey", out val))
{
}
3) From your description of your requirements you want to save MD5 hash codes for filenames
dic.Add("c:\\path\\filename.ext","123123134123123");