combobox not working with sql connection reader : 

    `

private void comboBox45_SelectedIndexChanged(object sender, EventArgs e)
        {

           
            baglanti.Open();
            string str = "select * from satilikkonutlar where ilanbasligi='" + comboBox45.Text.Trim() + "";
            SqlCommand com = new SqlCommand(str, baglanti);

            SqlDataReader reader = com.ExecuteReader(); ``           
            while (reader.Read())
            {
                textBox4.Text = reader["fiyat"].ToString();
            }
            reader.Close();
            baglanti.Close();
    enter code here

reader not working help me guys ty.