我在panel控件里面有checkbox控件,現在我要后臺遍歷checkbox的值,請問下面這樣做為什么會有錯誤呢,應該怎么樣做才行呢?        foreach (Control c in sheshi.Controls)        {            CheckBox cb = ( CheckBox)c;            if (cb.Checked)                ht.SheBei += "," + cb.Text;        }