adding new row to new row to webgrid in mvc 4

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MVC4

I have few textboxes followed by webgrid. Textboxes like suppliername,age ,address.
webgrid each consist of dropdown for category,dropdown for product,textbox for productvlaue and discount.

now the problem is when click on save button,save action is getting called but the model fields are empty.The next problem how to add new row to webgrid without losing previous values using model concept not by jquery's append method for table.