avoid saving empty rows into database

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C#

i use the code below to save data into sql database. each row is given a unique number (IDENTITY) it works alright but always saves the last row on the gridview which does not contain any data. HOW do i prevent this

code

for (int i = 0; i < dgvCategory.Rows.Count; i++)
                        {
                            StrQuery = @"INSERT INTO CategorynA VALUES ('" + this.txtCategory.Text + "', '" + dgvCategory.Rows[i].Cells["clmActivity"].Value + "');";
                            comm.CommandText = StrQuery;
                            conn.Open();
                            comm.ExecuteNonQuery();
                            conn.Close();
                        }