优化后的标题：在Asp.net中动态加载DropDownList控件的数据源方法与技巧

CREATE TABLE [dbo].[mail_type]
([MailNo] [varchar] (20) COLLATE Chinese_Taiwan_Stroke_CI_AS NOT NULL,[MailType] [nvarchar] (100) COLLATE Chinese_Taiwan_Stroke_CI_AS NOT NULL,[Remark] [nvarchar] (500) COLLATE Chinese_Taiwan_Stroke_CI_AS NULL,[Status] [char] (1) COLLATE Chinese_Taiwan_Stroke_CI_AS NOT NULL
) GO

"drpMailType" runat&＃61;"server">

if (this.drpMailType.SelectedValue.Length > 0)string sqlQuery &＃61;string.Format(" AND MailType &＃61; {0}", this.drpMailType.SelectedValue.Trim());

"drpSex" runat&＃61;"server">"">--select--"男" Selected&＃61;"True">男"女">女

public DataTable GetMailTypeList(){string cmdText &＃61; "SELECT DISTINCT MailNo,MailType FROM mail_type ORDER BY MailType";SqlConnection myConnection &＃61; new SqlConnection(ConfigurationSettings.AppSettings["Key_Name"]);SqlDataAdapter myCommand &＃61; new SqlDataAdapter(cmdText, myConnection);DataSet ds &＃61; new DataSet();DataTable dt &＃61; ds.Tables["tableName"];return dt;
}

public void GetDropInfo(DropDownList obj, string firstItemText, string firstItemValue, string defValue) {obj.Items.Clear(); // 清除加载&＃xff0c;防止多次加载&＃xff0c;出现重叠的状况DataTable dt &＃61; GetMailTypeList();if (dt !&＃61; null && dt.Rows.Count > 0) {foreach (DataRow dr in dt.Rows) {obj.Items.Add(new ListItem(dr["MailNo"].ToString() &＃43; " " &＃43; dr["MailType"].ToString(), dr["MailNo"].ToString()));}}
// 设置的第一个值&＃xff0c;如“--select--”if (firstItemText !&＃61; null && firstItemValue !&＃61; null)obj.Items.Insert(0, new ListItem(firstItemText, firstItemValue));//默認值if (!string.IsNullOrEmpty(defValue) && obj.Items.FindByValue(defValue) !&＃61; null)obj.SelectedValue &＃61; defValue;
}

obj.Items.Add(new ListItem(dr["MailNo"].ToString() &＃43; " " &＃43; dr["MailType"].ToString(), dr["MailNo"].ToString()));
可以替换成
obj.Items.Add(new ListItem(string.Format("({0}) {1}", dr["MailType"].ToString(), dr["MailTypeDesc"].ToString()), dr["MailType"].ToString()));

//把SQL语句改下

string cmdText &＃61; "SELECT DISTINCT MailType FROM mail_type ORDER BY MailType";

if (dt !&＃61; null && dt.Rows.Count > 0) {obj.DataValueField &＃61; "MailType";
　 obj.DataTextField &＃61; "MailType";
　 obj.DataSource &＃61; dt.DefaultView; obj.DataBind(); }

GetMailTypeInfo(this.drpMailType, "--select--", "", null);

GetMailTypeInfo(this.drpMailType,"--select--","",this.drpMailType.SelectedValue);