c# - Override property on IEnumerable object -

i have object:

var child = mapper.map<list<childviewmodel>>( model.childdata ); 

and return this:

return new outputviewmodel   {       childdata = child   };  

but in middle need perform change in 1 of child property, tried this:

var dummy = child.select(e => e.number = formatnumber(e.number, e.mask)); 

so when return outputviewmodel job done, have number property formatted, there better way because don't :(

why not make read-only property has number formatted?

public class outputviewmodel {     public decimal number { get; set; }     public object mask { get; set; }     public string numberformatted      {         { return formatnumber(number, mask); }     } }