Each expression returns a value that depends only on the operands of the expression, and no expression has any side effects.
每个表达式仅根据其操作数来返回值，并且都不会产生副作用。
If model data referenced by a value binding expression is no longer available or has changed prior to the component tree being restored, it can result in portions of the tree being dropped.
如果一个值绑定表达式引用的模型数据不再可用，或者在组件树被恢复之前发生了更改，那么组件树的一些部分将被撤销。
In the case where a retrieved column has a value of SQL NULL, then no XPath variable reference expression is assigned to such a value.
如果检索到的列值为SQLNULL，那么不会给此类值分配任何XPath变量引用表达式。
In the case where a retrieved column has a value of SQL NULL, then no XPath variable reference expression is assigned to such a value.
如果检索到的列值为SQLNULL，那么不会给此类值分配任何XPath变量引用表达式。
应用推荐