DropDownList綁定顯示問題！ ——轉

DropDownList綁定顯示問題！
這是一個DropDownList網上註冊選擇所在地的DropDownList一共有兩個DropDownList一個是省一個是市連動反映選擇省自己 列出市但是我想讓它在瀏覽的時候美觀一些在DropDownList加上“請選擇省”和“請選擇市”
我是這樣加的但是出錯
this.car_dq1.Items.Insert(0,new   ListItem( "——請選擇省—— ", " "));
出錯內容是：sdr=cmdCity.ExecuteReader();着句話出錯！
說“=”號附近有語法錯誤！請高手看看！

china是省表名
china_id是省編號
china_name是省名稱字段

city是市表名
city_id市編號
china_id是外鍵
city_name市名稱

car_dq1是省的DropDownList
car_dq2是市的DropDownList


private   void   Page_Load(object   sender,   System.EventArgs   e)
{
if(!IsPostBack)
{
SqlConnection   con=carlhb.createConnection();
con.Open();
SqlCommand   cmd=new   SqlCommand( "select   *   from   china ",con);
SqlDataReader   sdr=cmd.ExecuteReader();
this.car_dq1.DataSource=sdr;
this.car_dq1.DataTextField= "china_name ";
this.car_dq1.DataValueField= "china_id ";
this.car_dq1.DataBind();
this.car_dq1.Items.Insert(0,new   ListItem( "——請選擇省—— ", " "));
sdr.Close();

SqlCommand   cmdCity=new   SqlCommand( "select   *   from   city   where   china_id= "+this.car_dq1.SelectedValue,con);
sdr=cmdCity.ExecuteReader();
this.car_dq2.DataSource=sdr;
this.car_dq2.DataTextField= "city_name ";
this.car_dq2.DataValueField= "city_id ";
this.car_dq2.DataBind();
this.car_dq2.Items.Insert(0,new   ListItem( "——請選擇市—— ", " "));
sdr.Close();
con.Close();
}

private   void   car_dq1_SelectedIndexChanged(object   sender,   System.EventArgs   e)
{
string   china_id=this.car_dq1.SelectedValue;
SqlConnection   con=carlhb.createConnection();
con.Open();
SqlCommand   cmd=new   SqlCommand( "select   *   from   city   where   china_id= "+china_id,con);
SqlDataReader   sdr=cmd.ExecuteReader();
this.car_dq2.DataSource=sdr;
this.car_dq2.DataTextField= "city_name ";
this.car_dq2.DataValueField= "city_id ";
this.car_dq2.DataBind();
}