How to reuse property fetched using Reflection

private static string GenerateStr<T>(IList<T> obj, string propName)
{
  string str = string.Empty;
  foreach(var o in obj)
  {
      str += o.GetType().GetProperty(propName).GetValue(o, null); 
          //is there a way to only call above line once, then call
          // str =+ o.myStrProp over the course of the iteration?

  }
  return str;
}

Is there a way to be able to reuse the fetched property to refrain from relying on Reflection to do it again for me. Thanks!