Should sumarize totals's column with blank rows as null or 0

Hi!

When I make a filter its stuggs or block. Doesnt do the filter. I realize that the my Totals's column have some blank rows. Then how can I do to considerate all blank rows as null or "0".

conn.Open();

OleDbCommand cmd = conn.CreateCommand();

cmd.CommandType = CommandType.Text;

cmd.CommandText = "select * from cadastramento where year= ?";

var param1 = new OleDbParameter("@year", OleDbType.VarChar); // use actual type of 'name' here

param1.Value = cbxYear.Text; // or whatever

cmd.Parameters.Add(param1);

cmd.ExecuteNonQuery();

DataTable dt = new DataTable();

OleDbDataAdapter da = new OleDbDataAdapter(cmd);

da.Fill(dt);

conn.Close();

dGVCons.DataSource = dt;

this.dGVCons.RowsDefaultCellStyle.BackColor = Color.AliceBlue;

this.dGVCons.AlternatingRowsDefaultCellStyle.BackColor = Color.Beige;

int sum = 0;

for (int i = 0; i < dGVCons.Rows.Count; ++i)

{

sum += Convert.ToInt32(dGVCons.Rows[i].Cells["total_Clothes"].Value);

lblTotalClothes.Text = " " + sum.ToString();

int sum1 = 0;

for (int i1 = 0; i1 < dGVCons.Rows.Count; ++i1)

{

sum1 += Convert.ToInt32(dGVCons.Rows[i1].Cells["total_Shoes"].Value);

lblTotalShoes.Text = " " + sum1.ToString();