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You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. 
You write the following code segment. (Line numbers are included for reference only.) 

the TextBox control is data-bound to an instance of the Contact class.  
You need to ensure that the Contact class contains a business rule to ensure that the ContactName property is not empty or NULL.
You also need to ensure that the TextBox control validates the input data. 
Which two actions should you perform?（）

唐代佛学盛行对诗歌创作艺术上最消极的影响是（）。 以禅法入诗。 以禅语入诗。 以禅趣入诗。 以禅境入诗。 中国第一位大力写作五言诗的文人是（） 曹植。 曹丕。 曹操。 阮籍。 You are the network administrator for your company. The network consists of a single Active Directory domain. All servers run Windows Server 2003. You need to update six high-visibility servers with critical updates by using Windows Server Update Services （WSUS）. You approve all of the updates. You need to ensure that the updates are applied within one hour. What should you do？（） On the WSUS server， type the gpupdate /force command at the command prompt.。 On the WSUS server， type the wuauclt /detectnow command at the command prompt.。 On each of the six servers， type the gpupdate /force command at the command prompt.。 On each of the six servers， type the wuauclt /detectnow command at the command prompt.。 财务杠杆率大于1，表明公司基期的息税前利润不足以支付当期债息。 招标人事先经过考察和筛选，将投标邀请书发给某些特定的法人或者组织，邀请其参加投标的这种招标方式叫（） 公开招标。 邀请招标。 自行招标。 委托招标。

You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. 
You write the following code segment. (Line numbers are included for reference only.) 

the TextBox control is data-bound to an instance of the Contact class.  
You need to ensure that the Contact class contains a business rule to ensure that the ContactName property is not empty or NULL.
You also need to ensure that the TextBox control validates the input data. 
Which two actions should you perform?（）