Question

I have a simple interface with methods such as

     bool TryGetValue(string key, out string value);
     bool TryGetValue(string key, out int value);
     bool TryGetValue(string key, out double value);
     bool TryGetValue(string key, out DateTime value);
     // only value types allowed 

     //with the implementation based on dictionary<string, object> 
     bool TryGetValue(string key, out string value)
     {
        object rc;
        if ( dict.TryGetValue(key, out rc) )
        {
            value = rc.ToString();
            return true;
        }

        value = null;
        return false;
     }

Looks like a perfect case for generics as

     bool TryGetValue<T>(string key, out T value) where T: ValueType;

except not able to work out the func implementation, anyone ?

UPDATE – the following does not compile, i’d like to avoid creating multiple TryGet… funcs !

     bool TryGetValue<T>(string key, out T value)
     {
         return dict.TryGetValue(key, out value) ;
     }

Answer 1

Try this:

public bool TryGetValue<T>(string key, out T value) where T : struct
{
  object obj;
  var result = dict.TryGetValue(key, out obj);
  value = (T)obj;
  return result;
}

It’ not pretty, but deals with the limitations of out…maybe someone can shorten it even more? If so please comment…always up to learn new ways.