sql error - missing a (;) at the end of sql statement
INSERT INTO photoDB(fileNames)
VALUES('" + Path.GetFileName(fileName) + "')
ON DUPLICATE KEY UPDATE fileNames = 1

SqlConnection conn = new SqlConnection("ConnectionString");

SqlCommand command = new SqlCommand();
command.Connection = conn;
command.CommandText = "INSERT INTO photoDB (fileNames) VALUES(@fileName) ON DUPLICATE KEY UPDATE fileNames = 1;";
command.Parameters.Add(new SqlParameter("@filename", System.Data.SqlDbType.VarChar).Value = Path.GetFileName(fileName));
command.ExecuteNonQuery();