一. C# 原始代码和直接结果
测试 C# 代码：
class Program
{
static void Main(string[] args)
{
A c1 = new C();
c1.Foo(); C c2 = new C();
c2.Foo(); Console.ReadKey();
}
}
class A
{
public virtual void Foo()
{
Console.WriteLine("Call on A.Foo()");
}
}
class B : A
{
public override void Foo()
{
Console.WriteLine("Call on B.Foo()");
}
}
class C : B
{
public new void Foo()
{
Console.WriteLine("Call on C.Foo()");
}
}
运行结果：
二. IL程序编译的IL代码执行结果
IL 代码：
.assembly extern mscorlib
{
auto
}
.assembly MyTest{}
.module MyTest.exe .class public A
{
.method public specialname void .ctor()
{
ldarg.0
call instance void [mscorlib]System.Object::.ctor()
ret
} .method public newslot virtual void Foo()
{
ldstr "Call on A.Foo()"
call void [mscorlib]System.Console::WriteLine(string)
ret
}
}
.class public B extends A
{
.method public specialname void .ctor()
{
ldarg.0
call instance void A::.ctor()
ret
} .method public virtual void Foo()
{
ldstr "Call on B.Foo()"
call void [mscorlib]System.Console::WriteLine(string)
ret
}
}
.class public C extends B
{
.method public specialname void .ctor()
{
ldarg.0
call instance void B::.ctor()
ret
} .method public void Foo()
{
ldstr "Call on C.Foo()"
call void [mscorlib]System.Console::WriteLine(string)
ret
}
}
.method public static void Main()
{
.entrypoint
.locals (class A v_0,class C v_1)
newobj instance void C::.ctor()
stloc.0
ldloc.0
callvirt instance void A::Foo()
newobj instance void C::.ctor()
stloc.1
ldloc.1
callvirt instance void C::Foo()
call valuetype [mscorlib]System.ConsoleKeyInfo [mscorlib]System.Console::ReadKey()
pop
ret
}
运行结果：
三. 用 Call 代替 CallVirt 的 IL
IL 代码：
.assembly extern mscorlib
{
auto
}
.assembly MyTest{}
.module MyTest.exe .class public A
{
.method public specialname void .ctor()
{
ldarg.0
call instance void [mscorlib]System.Object::.ctor()
ret
} .method public newslot virtual void Foo()
{
ldstr "Call on A.Foo()"
call void [mscorlib]System.Console::WriteLine(string)
ret
}
}
.class public B extends A
{
.method public specialname void .ctor()
{
ldarg.0
call instance void A::.ctor()
ret
} .method public virtual void Foo()
{
ldstr "Call on B.Foo()"
call void [mscorlib]System.Console::WriteLine(string)
ret
}
}
.class public C extends B
{
.method public specialname void .ctor()
{
ldarg.0
call instance void B::.ctor()
ret
} .method public void Foo()
{
ldstr "Call on C.Foo()"
call void [mscorlib]System.Console::WriteLine(string)
ret
}
}
.method public static void Main()
{
.entrypoint
.locals (class A v_0,class C v_1)
newobj instance void C::.ctor()
stloc.0
ldloc.0
call instance void A::Foo()
newobj instance void C::.ctor()
stloc.1
ldloc.1
call instance void C::Foo()
call valuetype [mscorlib]System.ConsoleKeyInfo [mscorlib]System.Console::ReadKey()
pop
ret
}
运行结果：
四. 结论
如果使用 Call 的话，它会简单粗暴的指针调用代码，即 A 中的 Foo 方法的代码进行执行。