Preview
Name Surname Marital status Age Birthday Employed
Joe Crosswave Married 32 1/5/1992 False
Merry Lisel Widowed 42 5/6/1982
Henry Crux Single 30 11/19/1994 True
Cody Jurut 50 8/11/1974 False
Simon Scranton Single 35 10/10/1989
Leena Laurent Divorced 20 7/1/2004 False
Ode Cosmides Married 54 4/17/1970 True
Diandra Mizner Single 21 8/20/2003 False
Pete Cassel Married 23 3/13/2001 False
Nicky Tremblay Married 32 1/5/1992 True
Mary Cassel Married 25 7/10/1999 True
Average 33
View 

@model IQueryable<Person>

@(Html
    .Grid(Model)
    .Build(columns =>
    {
        columns.Add(model => model.Name).Titled("Name");
        columns.Add(model => model.Surname).Titled("Surname");
        columns.Add(model => model.MaritalStatus).Titled("Marital status");

        columns.Add(model => model.Age).Titled("Age");
        columns.Add(model => model.Birthday).Titled("Birthday").Formatted("{0:d}");
        columns.Add(model => model.IsWorking).Titled("Employed");
    })
    .UsingFooter("_GridFooter")
)
_GridFooter partial view 

@model IGrid<Person>

<tr>
    <td colspan="3"><b>Average</b></td>
    <td><b>@(Model.Rows.Average(row => row.Model.Age))</b></td>
    <td></td>
    <td></td>
</tr>