The contextual keyword 'var' may only appear within a local variable declaration issues

Question

I know what this means, and I have searched Google, and MSDN. But, how else am I going to get around this?

I have a function in my razor code inside the App_Code folder (using WebMatrix), and I get info from the database, do some calculations, then update the database with the new total.

But, how am I to pass variables to my method in the App_Code folder if it won't let me?

Here's what I've got:

EditQuantity.cshtml (root folder):

        try
        {
            Base baseClass;
            baseClass.CalculateTotalPriceInCart(Request.QueryString["PartNumber"], Request.QueryString["Description"], Session["OSFOID"], true);

            Response.Redirect("~/Cart.cshtml");
        }
        catch(Exception exmes)
        {
            message = exmes;
        }

And, Base.cs (inside App_Code folder):

using System;
using System.Collections.Generic;
using System.Web;
using System.Text;
using WebMatrix.Data;

/// <summary>
/// Summary description for ClassName
/// </summary>
public class Base
{   
    public void CalculateTotalPriceInCart(var PartNumber, var Description, var OrderId, bool IsBoxed)
    {
        var database = Database.Open("OSF");
        var query = "";
        var result = "";
        decimal price = 0.00M;

        if(IsBoxed)
        {
            // Select item.
            query = "SELECT Boxes, BoxPrice FROM Cart WHERE OrderId = '" + OrderId + "' AND PartNumber = '" + PartNumber + "' AND Description = '" + Description + "' AND IsBoxed = 1";
            result = database.Query(query);

            // Recalculate Price.
            foreach(var item in result)
            {
                price = result.Boxes * result.BoxPrice;
            }

            // Update item.
            query = "UPDATE Cart SET BoxPrice = '" + price + "' WHERE OrderId = '" + OrderId + "' AND PartNumber = '" + PartNumber + "' AND Description = '" + Description + "' AND IsBoxed = 1";
            database.Execute(query);
        }
    }
}

I've tried a few things to see if it'd work, but nope. I'm obviously doing it wrong, but this is how I do it in Desktop apps, I don't get why it'd be different here for WebPages, and how shold I go about doing this?

Thank you!