[InfoPath] Form XPathNavigator Request Failed

Request Failed Infopath Form

Dim ABC As XPathNavigator = Me.MainDataSource.
Dim nodeABC As XPathNavigator = ABC.SelectSingleNode("/my:myFields/my:abc", Me.NamespaceManager)

How to solve it? / 如何解决？
1. Go to Tools -> Form Options
2. Click Security and Trust link in left pane, then select the radio "Full Trust" in right hand pane.

1. 去 Tools -> Form Options
2. 点击 Security and Trust, 然后打勾 "Full Trust", 完成