If you are trying to insert all the records that you have in your datatable than iterate through those records while calling the stored procedure . In your submit event you are inserting values from your textboxes which will be the last one you have on your web page when you hit the submit button.
for (int i = 0; i < GridView1.Rows.Count; i++)
{
string Name =GridView1.Rows[i].Cells[0].Text.Trim();
....
....
InsertMyRecord(Name,...
}
Put your SQL code in a separate procedure and pass values to it(This is not essential but just a recommendation to make your code bit elegant).