Globalization Project To Convert Website Into French?

I am working with globalization project to convert website into french.In ProductData.cs page I have function called GetProductDetails as below.

public static Product GetProductDetails(int productId)
{
Product product = null; [code]...

All this work fine when CountryCode is 'US' and language culture is 'en-US'.But when I change to language culture to 'fr-FR' through internet explorer it shows error in ProductDetails.cs page that ''object instance not set to reference"

DataAccess.cs used in above code is as follow.

public static product GetProducgDetails(int productId)
{
Product product = ProductData.GetProductDetails(productId);
return product;
}

.How can I remove error I am getting in Productdetails.cs page