call、callvirt和calli指令用于完成方法调用，有何区别呢？
1）call使用静态调度，也就是根据引用类型的静态类型来调度方法。call指令根据引用变量的类型来调用方法，因此通常用于调用非虚方法。
2）callvirt使用虚拟调度，也就是根据引用类型的动态类型来调度方法；callvirt指令根据引用变量指向的对象类型来调用方法，执行时会递归的调用给自己知道堆栈溢出，从而实现了在运行时的动态绑定，因此通常用于调用虚方法。
3）calli又称间接调用，是通过函数指针来执行方法调用的。与call和callvirt相对应的（直接调用）
Father类
public class Father
{
public void DoWork()
{
Console.WriteLine("Father.DoWork()");
} public virtual void DoVirtualWork()
{
Console.WriteLine("Father.DoVirtualWork()");
} public virtual void DoVirtualAll()
{
Console.WriteLine("Father.DoVirtualAll()");
}
}
Son类
public class Son:Father
{
public static void DoStaticWork()
{
Console.WriteLine("Son.DoStaticWork()");
} public new void DoWork()//new表示对父类的阻断
{
Console.WriteLine("Son.DoWork()");
} public new virtual void DoVirtualWork()
{
Console.WriteLine("Son.DoVirtualWork()");
} public override void DoVirtualAll()
{
base.DoVirtualAll();
Console.WriteLine("Son.DoVirtualAll()");
}
}
GrandSon类
public class GrandSon:Son
{
public override void DoVirtualWork()
{
base.DoVirtualWork();
Console.WriteLine("GrnadSon.DoVirtualWork()");
} public override void DoVirtualAll()
{
base.DoVirtualAll();
Console.WriteLine("GrandSon.DoVirtualAll()");
}
}
Prgram.cs
class Program
{
static void Main(string[] args)
{
Father son = new Son();
son.DoWork();
son.DoVirtualWork(); Son.DoStaticWork(); Father aGrandSon = new GrandSon();
aGrandSon.DoWork();
aGrandSon.DoVirtualWork();
aGrandSon.DoVirtualAll(); Console.ReadLine();
}
}
输出结果
IL代码
.method private hidebysig static void Main(string[] args) cil managed
{
.entrypoint
// 代码大小 61 (0x3d)
.maxstack 1
.locals init ([0] class ConsoleApplication1.Father son,
[1] class ConsoleApplication1.Father aGrandSon)
IL_0000: nop
IL_0001: newobj instance void ConsoleApplication1.Son::.ctor()
IL_0006: stloc.0
IL_0007: ldloc.0
IL_0008: callvirt instance void ConsoleApplication1.Father::DoWork()
IL_000d: nop
IL_000e: ldloc.0
IL_000f: callvirt instance void ConsoleApplication1.Father::DoVirtualWork()
IL_0014: nop
IL_0015: call void ConsoleApplication1.Son::DoStaticWork()
IL_001a: nop
IL_001b: newobj instance void ConsoleApplication1.GrandSon::.ctor()
IL_0020: stloc.1
IL_0021: ldloc.1
IL_0022: callvirt instance void ConsoleApplication1.Father::DoWork()
IL_0027: nop
IL_0028: ldloc.1
IL_0029: callvirt instance void ConsoleApplication1.Father::DoVirtualWork()
IL_002e: nop
IL_002f: ldloc.1
IL_0030: callvirt instance void ConsoleApplication1.Father::DoVirtualAll()
IL_0035: nop
IL_0036: call string [mscorlib]System.Console::ReadLine()
IL_003b: pop
IL_003c: ret
} // end of method Program::Main