C＃区别铸造和as？ [英] C# difference between casting and as?
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问题描述
Possible Duplicate:
What is the difference between the following casts in c#?
之间的区别是什么？
在C＃中，转换对象或使用作为关键字有区别吗？希望这段代码会说明我的意思...
In C#, is a there difference between casting an object or using the as keyword? Hopefully this code will illustrate what I mean...
String text = "Hello hello";
Object obj = text;
String originalCast = ((String)obj).ToUpper();
String originalAs = (obj as String).ToUpper();
感谢
:)
推荐答案
as $ c> InvalidCastException 。相反，如果转换失败（它会给你一个 NullReferenceException 如果 obj 在你的示例中不是一个 string ）。
as will never throw a InvalidCastException. Instead, it returns null if the cast fails (which would give you a NullReferenceException if obj in your example were not a string).
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