c#中out和ref使用小结
1、out必须在函数体内初始化,在外面初始化没意义。也就是说,out型的参数在函数体内不能得到外面传进来的初始值。
2、ref必段在函数体外初始化。
3、两都在函数体的任何修改都将影响到外面
ref是传递参数的地址,out是返回值,两者有一定的相同之处,不过也有不同点。
使用ref前必须对变量赋值,out不用。
out的函数会清空变量,即使变量已经赋值也不行,退出函数时所有out引用的变量都要赋值,ref引用的可以修改,也可以不修改。
区别可以参看下面的代码:
2、ref必段在函数体外初始化。
3、两都在函数体的任何修改都将影响到外面
ref是传递参数的地址,out是返回值,两者有一定的相同之处,不过也有不同点。
使用ref前必须对变量赋值,out不用。
out的函数会清空变量,即使变量已经赋值也不行,退出函数时所有out引用的变量都要赋值,ref引用的可以修改,也可以不修改。
区别可以参看下面的代码:
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using system;
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class testapp
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{
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static void outtest(out int x, out int y)
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{/离开这个函数前,必须对x和y赋值,否则会报错。
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/y = x;
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/上面这行会报错,因为使用了out后,x和y都清空了,需要重新赋值,即使调用函数前赋过值也不行
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x = 1;
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y = 2;
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}
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static void reftest(ref int x, ref int y)
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{
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x = 1;
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y = x;
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}
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public static void main()
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{
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/out test
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int a,b;
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/out使用前,变量可以不赋值
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outtest(out a, out b);
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console.writeline("a={0};b={1}",a,b);
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int c=11,d=22;
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outtest(out c, out d);
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console.writeline("c={0};d={1}",c,d);
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/ref test
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int m,n;
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/reftest(ref m, ref n);
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/上面这行会出错,ref使用前,变量必须赋值
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int o=11,p=22;
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reftest(ref o, ref p);
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console.writeline("o={0};p={1}",o,p);
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}
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}
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