Question

now I can not get the correct information

   List<HeaderHelper> h = pr.Actual_View();
   foreach (TemplateHeader t in pr.TemplateView()) 
   {
      var v= h.Where(z => z.Country == t.Pais 
                       && z.dia == t.diaTotal 
                       && z.Segment == t.Segmento).FirstOrDefault();
   }

The

    pr.Actual_View()

is a class method for a list containing the following fields:

• Country (string)
• dia (int)
• Segment (string)

The

    pr.TemplateView()

is a class method for list containing the same fields and same datatype

the list t may contain more information than the list h, so I need to filter the list h with several criteria, but when I run the code does not correctly filter the list, returning a null.

Answer 1

If v is null, that suggests that none of the values in t matched your Where clause, so FirstOrDefault returned the default value of TemplateHeader, which is null.

Without more information or sample data we’ve got absolutely no way of knowing why none of the values in t matched, but that’s what the null value of v indicates.