Problem inserting a record to database

SqlConnection cnn = new SqlConnection(cs.constring());
SqlDataAdapter adapter = new SqlDataAdapter();

string sql = "insert into tblstudent (sno,s_name,gender,age,birthday,civil_status,place_of_birth,address,citizenship,religion,blood_type,mobile,telephone,email,father,f_occupation,mother,m_occupation,guardian,g_relationship,g_address,g_mobile,admission_date) values('" + txtsno.Text + "','" +
   txtname.Text + "','" + cbogender.Text + "','" + txtage.Text + "','" + dtpbirthday.Text + "','" + cbostatus.Text + "','" + txtplaceofbirth.Text + "','" + txtaddress.Text + "','" + txtcitizenship.Text + "','" + txtreligion.Text + "','" + txtbloodtype.Text + "','" + txtmobile + "','" +
   txttel.Text + "','" + txtemail.Text + "','" + txtfather.Text + "','" + txtfoccupation.Text + "','" + txtmother.Text + "','" + txtmoccupation + "','" + txtguardian.Text + "','" + txtrelationship.Text + "','" + txtgaddress + "','" + txtgmobile.Text + "','" + dtpadmission.Text + "')";

if (MessageBox.Show("do you want to save?", "choose an option", MessageBoxButtons.YesNo) == DialogResult.Yes)
{
    try
    {
        cnn.Open();
        adapter.InsertCommand = new SqlCommand(sql, cnn);
        adapter.InsertCommand.ExecuteNonQuery();
        MessageBox.Show("record saved !! ");
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.ToString());
    }
}
else
{

}