insert method - Input string was not in a correct format error

I am trying to insert data from the gridview into my database table "art_port".  I am only inserting one column from the gridview into my database table.  When I execute the insert method, it throws a exception error -->  Input string was not in a correct format.
I have verified that my insert statement matches my fieldnames as my 'art_port' table's fieldnames.  

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