Question

quandry is – which of the following two method performs best
Goal – get an object of type Wrapper ( defined below )
criteria – speed over storage
no. of records – about 1000- about 2000, max about 6K
Choices – Create Object on the fly or do a lookup from a dictionary
Execution speed – called x times per second

NB – i need to deliver the working code first and then go for optimization hence if any theorists can provide glimpses on behind the scene info, that’ll help before i get to the actual performance test possibly by eod thu

Definitions –

class Wrapper  
{  
   public readonly DataRow Row;  
   public Wrapper(DataRow dr)  
   {  
      Row = dr;  
   }  
   public string ID { get { return Row["id"].ToString(); } }  
   public string ID2 { get { return Row["id2"].ToString(); } }  
   public string ID3 { get { return Row["id3"].ToString(); } }  
   public double Dbl1 { get { return (double)Row["dbl1"]; } }  
   // ... total about 12 such fields !  
}  
Dictionary<string,Wrapper> dictWrappers;  

Method 1

Wrapper o = new Wrapper(dr);  
/// some action with o
myMethod( o );

Method 2

Wrapper o;    
if ( ! dictWrappers.TryGetValue( dr["id"].ToString(), out o ) )    
{    
    o = new Wrapper(dr);    
    dictWrapper.Add(o.ID, o);    
}    

/// some action with o    
myMethod( o );    

Answer 1

The first one would be faster, since it isn’t actually doing a lookup, it is just doing a simple allocation and an assignment.

The two segments of code are not nearly equivalent. In function however, because Method 1 could create many duplicates.