关于数据类型转换的补充知识

is（检查对象是否与给定类型兼容）

object o = new object();
2

o = "hello";
3

System.Console.WriteLine("\"hello\"-string->{0}", o is string);
4

o = 123;
5

System.Console.WriteLine("123-string->{0}", o is string);
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System.Console.WriteLine("123-String->{0}", o is String);
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System.Console.WriteLine("123-int->{0}", o is int);
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System.Console.WriteLine("123-Int32->{0}", o is Int32);
9

System.Console.WriteLine("123-Int16->{0}", o is Int16);
10

DateTime d = DateTime.Now;
11

System.Console.WriteLine("Now-DateTime->{0}", d is DateTime);
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string dd = "2006-01-01";
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System.Console.WriteLine("\"2006-01-01\"-DateTime->{0}", dd is DateTime);

as（用于在兼容的引用类型之间执行转换）

//as只用于引用类型
2

object o = new object();
3

o = "hello";
4

System.Console.WriteLine(o as string);
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o = 123;
6

System.Console.WriteLine(o as string);
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System.Console.WriteLine(o as String);
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//System.Console.WriteLine(o as int); as对值类型无效
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//System.Console.WriteLine(o as Int32); as对值类型无效
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//System.Console.WriteLine(o as Int16); as对值类型无效
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//DateTime d = DateTime.Now; as对值类型无效
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//System.Console.WriteLine(d as DateTime); as对值类型无效
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//string dd = "2006-01-01"; as对值类型无效
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//System.Console.WriteLine(dd as DateTime); as对值类型无效

checked/unchecked（对整型算术运算和显式转换启用溢出检查，否则算术运算回绕）
还记得我们前面对byte的一个转换吧，再看看下面，你就有更深的理解

byte b = 100;
2

System.Console.WriteLine((byte)(b + 200));//不抛出异常
3

System.Console.WriteLine(checked((byte)(b + 200)));//抛出异常
4

System.Console.WriteLine(unchecked((byte)(b + 200)));//不抛出异常