I have completed working through the eCommerce module and I've been on this error for 2 days. Everything seems to work fine, adding, editing departments, products, etc.

But when clicking "Add to Shopping Cart" button (btnAddToCart_Click), I get the exception below.

Any suggestion on why this is thrown is appreciated ?
/************************************************** ******/
Source File: ShoppingCart.aspx.cs Line: 45

Exception Details: System.FormatException: Input string was not in a correct format.

Source Error:
Line 43: // display the subtotal and the total amounts
Line 44: lblSubtotal.Text = this.FormatPrice(this.Profile.ShoppingCart.Total);
--> Line 45: lblTotal.Text = this.FormatPrice(this.Profile.ShoppingCart.Total +
Line 46: Convert.ToDecimal(ddlShippingMethods.SelectedValue ));
/************************************************** ******/

Please IGNORE my problem. But maybe it'll help bring insight

I found the problem, it had nothing to do with the code. As I mentioned I added department and products. What I didn't add was "Shipping Methods". Therefore leaving it 'null' and unable to Convert.ToDecimal. Adding a Shipping Method with an amount fixed it.