error ในการ search ข้อมูลครับ ไม่ทราบว่าเป็นข้อมูลแบบ ไหน ต้องโค๊ดดักอย่างไรครับ

 private void search()
        {

            if (conn.State == ConnectionState.Closed)
                conn.Open();
            SqlDataAdapter sda = new SqlDataAdapter(
            "select (materials.id),(materials.private_code),(materials.mat_code),(materials.serial),(materials.name),(materials.unit_name),(materials.description),(materials.remark),isnull(mat_onhands.quantity,0) as quantity FROM materials LEFT JOIN mat_onhands ON materials.id=mat_onhands.material_id where (materials.mat_group_id like'" + P_group.SelectedValue + "%' and materials.mat_category_id like'" + P_category.SelectedValue + "%' and(materials.name like'" + text_search.Text + "%' or materials.serial like'" + text_search.Text + "%') )"
           , conn);
            DataTable dt = new DataTable();
            sda.Fill(dt);
            dataGridView1.Rows.Clear();
            foreach (DataRow item in dt.Rows)
            {
                int n = dataGridView1.Rows.Add();
                dataGridView1.Rows[n].Cells[0].Value = item["private_code"].ToString();
                dataGridView1.Rows[n].Cells[1].Value = item["mat_code"].ToString();
                dataGridView1.Rows[n].Cells[2].Value = item["serial"].ToString();
                dataGridView1.Rows[n].Cells[3].Value = item["name"].ToString();
                dataGridView1.Rows[n].Cells[4].Value = item["unit_name"].ToString();
                dataGridView1.Rows[n].Cells[5].Value = item["description"].ToString();
                dataGridView1.Rows[n].Cells[6].Value = item["remark"].ToString();
                dataGridView1.Rows[n].Cells[7].Value = item["quantity"].ToString();        
            }
            conn.Close();
            if (dataGridView1.Rows.Count == 0)
            {
                MessageBox.Show("No Material Data ", "Result", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            text_search.Clear();
            text_search.Focus();
        }

text_search.Text = (text_search.Text == "'")? "":text_search.Text;

MessageBox.Show("select (materials.id),(materials.private_code),(materials.mat_code),(materials.serial),(materials.name),(materials.unit_name),(materials.description),(materials.remark),isnull(mat_onhands.quantity,0) as quantity FROM materials LEFT JOIN mat_onhands ON materials.id=mat_onhands.material_id where (materials.mat_group_id like'" + P_group.SelectedValue + "%' and materials.mat_category_id like'" + P_category.SelectedValue + "%' and(materials.name like'" + text_search.Text + "%' or materials.serial like'" + text_search.Text + "%') )")

private string S(string txt)
        {
                return "\'" + txt.Replace("\'", "\'\'") + "\'";
        }
private void search()
{
       string Sqlcmd;
       SqlCmd=" select * from TableName where field1=" + S(txtsearch.text);
}

private void text_search_TextChanged(object sender, EventArgs e)
        {
            text_search.Text = (text_search.Text.Substring(0, 1) == "'") ? text_search.Text.Substring(1, text_search.Text.Length-1) : text_search.Text;
            text_search.Text = (text_search.Text.Substring(text_search.Text.Length-1, 1) == "'") ? text_search.Text.Substring(0, text_search.Text.Length-1) : text_search.Text;
        }

private void text_search_TextChanged(object sender, EventArgs e)
        {
            string[] cri = new string[] { "'", "เ", "ห", "ี", "้", "ย" };
            foreach (string s in cri)
            {
                text_search.Text = (text_search.Text.Substring(0, 1) == s) ? text_search.Text.Substring(1, text_search.Text.Length - 1) : text_search.Text;
                text_search.Text = (text_search.Text.Substring(text_search.Text.Length - 1, 1) == s) ? text_search.Text.Substring(0, text_search.Text.Length - 1) : text_search.Text;
            }
        }