C# For loop with if statement

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

    conn.Open();
    OleDbCommand cmd2 = new OleDbCommand();
    cmd2 = conn.CreateCommand();
    cmd2.CommandText = @"SELECT [Location] FROM [Barcodes] WHERE [Barcode] = '" + DGStock.Rows[i].Cells["Location"].Value + "'";
    cmd2.ExecuteNonQuery();
    conn.Close();


    if (DGStock.Rows[i].Cells["Location"].Value == "[Location]")
    {
        conn.Open();
        OleDbCommand cmd3 = new OleDbCommand();
        cmd3 = conn.CreateCommand();
        cmd3.CommandText = @"UPDATE [Barcodes] SET [Location] = '" + DGStock.Rows[i].Cells["Location"].Value + "' WHERE [Barcode] = '" + DGStock.Rows[i].Cells["Barcode"].Value + "'";
        cmd3.ExecuteNonQuery();
        conn.Close();                    
    }
    else
    {                   
        conn.Open();
        //string query =
        OleDbCommand cmd = new OleDbCommand();
        cmd = conn.CreateCommand();
        cmd.CommandText = @"INSERT INTO [Barcodes] (Location, Barcode) Values ('" + DGStock.Rows[i].Cells["Location"].Value + "','" + DGStock.Rows[i].Cells["Barcode"].Value + "')";
        cmd.ExecuteNonQuery();
        conn.Close();
    }

}