how to set selected value from database in combobox c#

private void Form1_Load(object sender, EventArgs e)
        {
cn.con.Open();
            DataTable dt = new DataTable();
            string sql = "SELECT * FROM STUDENTMAS";
            SqlDataAdapter da = new SqlDataAdapter(sql, cn.con);

            da.Fill(dt);
            dataGridView2.AutoGenerateColumns = false;
            dataGridView2.DataSource = dt;
            cn.con.Close();
        }

 

 

 

private void dataGridView2_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {

// load category comboBox2 =================================================

 

DB_CONNECTION cn = new DB_CONNECTION();
            cn.con.Open();
            cn.cmd.Connection = cn.con;
            cn.cmd.CommandText = "SELECT ID,NAME FROM CATEGORYTB ";
            System.Data.SqlClient.SqlDataReader dr;
            dr = cn.cmd.ExecuteReader();
            if (dr.HasRows)
            {
                combobox_id.Items.Clear();
                while (dr.Read())
                {
                    ComboboxItem item = new ComboboxItem();
                    item.Text = dr["NAME"].ToString();
                    item.Value = dr["ID"].ToString();
                    comboBox2.Items.Add(item);
                }
            }
            cn.con.Close();

 

//===================================================================

 

 // How to load category comboBox2 with a value of category field in studentmas table.

 

 // I try several processes, but not load

 

//comboBox1.SelectedIndex = comboBox1.FindStringExact(dataGridView2.Rows[e.RowIndex].Cells["ID"].Value.ToString());
 //comboBox1.SelectedValue = dataGridView2.Rows[e.RowIndex].Cells["ID"].Value.ToString();
 //comboBox1.SelectedIndex = comboBox1.Items.IndexOf(dataGridView2.Rows[e.RowIndex].Cells["ID"].Value.ToString());

}

 

 

Database table (categoryTB):

id	name	status_flag
C1	General	Y
C2	SC	Y
C3	ST	Y
C4	OBC	Y

 

DatabaseTable(studentmas) :

roll_no	name	session	semester	category
R1	Rahit	Autumn	2021	C1
R2	Rahon	Spring	2021	C1
R3	Smith	Spring	2021	C3
R5	Alam	Autumn	2021	C2

 

 

 

 Please help