how to insert data from combo box to sql database in connected mode?

private void button1_Click(object sender, EventArgs e)
     {

         using (SqlConnection con =
                new SqlConnection(@"Data Source=IT-DEV2\SQLEXPRESS;Initial Catalog=test;Integrated Security=True"))
         {
             con.Open();
             using (SqlCommand cmd = new SqlCommand("INSERT INTO dbo.cate (cate_id) values (@cate_id )", con))
             {
                 cmd.Parameters.AddWithValue("@cate_id", comboBox1.SelectedValue );

                 cmd.ExecuteNonQuery();
             }
         }

     }

cmd.Parameters.Add(new SqlParameter("@dept",SqlDbType.Int));
command.Parameters["@dept"].Value = comboBox_dept.SelectedValue;