查看override的IL
Override示例
下面我们看一个Override的Example
namespace MyCollection{ public class MyBase { public virtual string Meth1() { return "MyBase-Meth1"; }
public virtual string Meth2() { return "MyBase-Meth2"; }
public virtual string Meth3() { return "MyBase-Meth3"; } }
class MyDerived : MyBase { // 使用 override 关键字重写虚方法 Meth1: public override string Meth1() { return "MyDerived-Meth1"; }
// 使用 new 关键字显式隐藏 // 虚方法 Meth2: public new string Meth2() { return "MyDerived-Meth2"; }
// 由于下面声明中没有指定任何关键字 // 因此将发出一个警告来提醒程序员 // 此方法隐藏了继承的成员 MyBase.Meth3(): public string Meth3() { return "MyDerived-Meth3"; } } public class VirtualExample { public static void Main() { MyDerived mD = new MyDerived(); MyBase mB = (MyBase)mD;
System.Console.WriteLine(mD.Meth1()); System.Console.WriteLine(mD.Meth2()); System.Console.WriteLine(mD.Meth3()); System.Console.WriteLine("以上为类MyDerived的显示结果！\n");
System.Console.WriteLine(mB.Meth1()); System.Console.WriteLine(mB.Meth2()); System.Console.WriteLine(mB.Meth3()); System.Console.WriteLine("以上为MyBase的显示结果！\n"); System.Console.WriteLine("按任意键退出..."); System.Console.ReadLine(); } }}运行结果
IL查看
双击查看Main方法
IL代码
.method public hidebysig static void Main() cil managed{ .entrypoint // Code size 121 (0x79) .maxstack 1 .locals init ([0] class MyCollection.MyDerived mD, [1] class MyCollection.MyBase mB) IL_0000: nop IL_0001: newobj instance void MyCollection.MyDerived::.ctor() IL_0006: stloc.0 IL_0007: ldloc.0 IL_0008: stloc.1 IL_0009: ldloc.0 IL_000a: callvirt instance string MyCollection.MyBase::Meth1()//调用的是MyBase的Meth1() IL_000f: call void [mscorlib]System.Console::WriteLine(string) IL_0014: nop IL_0015: ldloc.0 IL_0016: callvirt instance string MyCollection.MyDerived::Meth2() IL_001b: call void [mscorlib]System.Console::WriteLine(string) IL_0020: nop IL_0021: ldloc.0 IL_0022: callvirt instance string MyCollection.MyDerived::Meth3() IL_0027: call void [mscorlib]System.Console::WriteLine(string) IL_002c: nop IL_002d: ldstr bytearray (E5 4E 0A 4E 3A 4E 7B 7C 4D 00 79 00 44 00 65 00 // .N.N:N{|M.y.D.e. 72 00 69 00 76 00 65 00 64 00 84 76 3E 66 3A 79 // r.i.v.e.d..v>f:y D3 7E 9C 67 01 FF 0A 00 ) // .~.g.... IL_0032: call void [mscorlib]System.Console::WriteLine(string) IL_0037: nop IL_0038: ldloc.1 IL_0039: callvirt instance string MyCollection.MyBase::Meth1()//这里一样调用的是MyBase的Meth1() IL_003e: call void [mscorlib]System.Console::WriteLine(string) IL_0043: nop IL_0044: ldloc.1 IL_0045: callvirt instance string MyCollection.MyBase::Meth2() IL_004a: call void [mscorlib]System.Console::WriteLine(string) IL_004f: nop IL_0050: ldloc.1 IL_0051: callvirt instance string MyCollection.MyBase::Meth3() IL_0056: call void [mscorlib]System.Console::WriteLine(string) IL_005b: nop IL_005c: ldstr bytearray (E5 4E 0A 4E 3A 4E 4D 00 79 00 42 00 61 00 73 00 // .N.N:NM.y.B.a.s. 65 00 84 76 3E 66 3A 79 D3 7E 9C 67 01 FF 0A 00 ) // e..v>f:y.~.g.... IL_0061: call void [mscorlib]System.Console::WriteLine(string) IL_0066: nop IL_0067: ldstr bytearray (09 63 FB 4E 0F 61 2E 95 00 90 FA 51 2E 00 2E 00 // .c.N.a.....Q.... 2E 00 ) // .. IL_006c: call void [mscorlib]System.Console::WriteLine(string) IL_0071: nop IL_0072: call string [mscorlib]System.Console::ReadLine() IL_0077: pop IL_0078: ret} // end of method VirtualExample::Main
IL解析
我们先回头看看源程序处的main内部的“System.Console.WriteLine(mD.Meth1());”语句对应上面的 IL_000a: callvirt instance string MyCollection.MyBase::Meth1() 和 IL_0039: callvirt instance string MyCollection.MyBase::Meth1()处的一模一样，原来它执行的是MyBase类的Meth1虚方法。而Meth1方法已经在 MyDerived类中重写了，所以这两个类的对应的方法1在本质说上都一样了。
通过看这个例子，我们能更加深入地理解override的功能了。看来ILdasm的确厉害，与其你想半天不如调IL代码看看，很多问题就会迎刃而解了，拨云见日啊！
