目录摘要：文章内容：引言：1.判php断NULL值：2.处理NULL值：3.避免NULL值的问题：4.注意事项和最佳实践：摘要：
In the case where Dictionary<object, object> myDictionary happens to contain a single item, what is the best way to retrieve the value object (if I don\'t care about the key) ?
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