c# auto mapper how to add auto-increment property to destination projection?

Question

We have source object "StockBase" and destination object as "StockDTO". While mapping "StockBase" to "StockDTO", we want to add a property that would give the index of collection ie auto increment by 1 in the "StockDTO" object.

For example "StockBase" has properties like Name, Owner, Color, Warranty.

While "StockDTO" has properties like Name, Owner + we want add Auto-increment-id that would give us rank of that Stock in collection starting from 1 and incremented by 1.

I read this but is there any better way to do this when mapping list to list without duplicating things in aftermap?

Answer 1

The only way to prevent iterating collection more than once that I could think of, would be something like this:

public class A {  }

public class B { public int Index { get;set; } }

var colA = new List<A>();
var colB = colA.Select((a, ix) => 
{
   var b = Mapper.Map<B>(a);
   b.Index = ix + 1;
   return b;
});

So, code iterates only once through the collection, and uses Mapper and its mapping profiles, in addition auto incremented property is assigned during projection.

Note: Usually, you will not use static Mapper class, rather you will use injected IMapper instance.