DataGrid View selection and export

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C#

As my project goes, I have a windows form with text boxes which will take sql id,sql ip, password,database name and sql query as input and will display data on a gridview and export the same to a csv file. Now the issue I am facing is I have to add another button which will export only the selected rows to csv file. The button which I have coded exports the whole data to csv. Can anyone please help me out with the code snippet for the second button which will export selected rows from grid view. Its really urgent. Thanks