关于DropDownList的怪问题

      DropDownList数据绑时，设置某个项被择，代码如下：

ddlMagazine.Items.FindByValue(_detail[0].MagazineCode).Selected = true;//一种Value查找
ddlMagazine.Items.FindByText(Doker.Biz.Magazine.MagazineRule.GetMagazineName(_detail[0].MagazineCode)).Selected = true;//另一种Text查找

运行如上代码时，ddlMagazine已经绑定了数据。
运行时出现以上错误：

Cannot have multiple items selected in a DropDownList.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Web.HttpException: Cannot have multiple items selected in a DropDownList.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

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Version Information: Microsoft .NET Framework Version:2.0.50727.42; ASP.NET Version:2.0.50727.42

解决的办法有两种：
      1.DropDownList数据绑时，设置某个项被择前，加如下代码：

ddlMagazine.ClearSelection();

      设置某项被选择的所以代码如下：

ddlMagazine.ClearSelection();//清除当前的选择
                            ddlMagazine.Items.FindByValue(_detail[0].MagazineCode).Selected = true;//设置选择例

      2.另一种通过SelectedIndex设置被选择的项，代码如下：

ddlMagazine.SelectedIndex = ddlMagazine.Items.IndexOf(ddlMagazine.Items.FindByValue(_detail[0].MagazineCode));

以上两种方法都是比较常见绑定DropDownList的某项被选择！

DropDownList绑定时，默认的是选择第一项为选择项，ddlMagazine.ClearSelection()可以清除选择项,然后重新设置选择项。