How to calculate total cart value from knockout mvc cart sample - asp.net-mvc

Question

I am trying to get my head around knockout mvc framework. I am looking at the sample of a shopping cart and trying to figure out:
How to calculate total cost
Where to add client side business rules (such as discounts and vouchers)
To calculate subtotal the code reads
#using (lines.If(m => m.ProductId != -1))
{
using (var product = lines.With(m => ko.Model.DataBase[m.CategoryId].Products[m.ProductId]))
{
#product.Html.Span(m => "\\$" + m.Price)
}
}
When I try to get the total from there I usually end up with a compiler exception or NullReferenceException in run time. For example
#using (lines.If(m => m.ProductId != -1))
{
using (var product = lines.With(m => ko.Model.Categories[m.CategoryId].Products[m.ProductId]))
{
#product.Html.Span(m => "\\$" + (lines.Model.Quantity * m.Price))
#{double total = lines.Model.Quantity * m.Price;}
}
}
Gives me
Compiler Error Message: CS1501: No overload for method 'Write' takes 0
arguments
Seems like I am doing it wrong. Would anyone point me in a right direction?

Answer 1

Have you tried removing the # symbol from the start of each line? I'm sure once you open a razor code block, you don't need to keep prepending every line with #. Also, not sure why the 'double total' line is wrapped in {}?
#using (var product = lines.With(m => ko.Model.Categories[m.CategoryId].Products[m.ProductId]))
{
product.Html.Span(m => "\\$" + (lines.Model.Quantity * m.Price));
double total = lines.Model.Quantity * m.Price;
}