Question

I’ve got a whole host of values stored in a .net 2.0 hashtable. What I would really like to find is a way to, essentially, do a SQL select statement on the table.

Meaning, I’d like to get a list of keys whose associated values match a very simple text pattern (along the lines of ‘starts with a number’.)

The final goal will be to remove these records from the hashtable for further processing.

I’ve been beating my head against this for a while now, and I can’t seem to come up with anything.

Any ideas?

(On the off chance this matters: due to the realities of this project, any 3rd party widgets or upgrading to a more recent version of .net are off the table.)

Answer 1

You could use a regex against every key in the hashtable. This is very dirty but it works:

    static void Main(string[] args)     {         Hashtable myhashtable = new Hashtable();         myhashtable.Add('Teststring', 'Hello');         myhashtable.Add('1TestString1', 'World');         myhashtable.Add('2TestString2', 'Test');          List<String> newht = new List<String>;          //match all strings with a number at the front         Regex rx = new Regex('^[1-9]');         foreach (string key in myhashtable.Keys)         {             if (rx.IsMatch(key) == true)             {                 newht.Add(key);             }         }          //Loop through all the keys in the new collection and remove them from         //them from the main hashtable.         foreach (string key in newht)         {             myhashtable.Remove(key);         }     } 

EDIT: And just for fun, here is the LINQ version (sorry I just had too).

            Hashtable myhashtable = new Hashtable();             myhashtable.Add('Teststring', 'Hello');             myhashtable.Add('1TestString1', 'World');             myhashtable.Add('2TestString2', 'Test');              Regex rx = new Regex('^[1-9]');             var k = (from string key in myhashtable.Keys                      where rx.IsMatch(key)                      select key).ToList();              k.ForEach(s => myhashtable.Remove(s)); 

EDIT: I have just added list of sting rather then a hashtable, I couldn’t remember which .net version had generic lists in it ***slaps forehead