今天在 WekeRoad.ActionPack里面看到如下

ApplyConfig(config, ref regexIgnoreCase, ConfigurationPropertyName.REGEX_IGNORE_CASE);


private static void ApplyConfig(System.Collections.Specialized.NameValueCollection config, ref string parameterValue, string configName)
        {
            if (config[configName] != null)
            {
                parameterValue = config[configName].ToString();
            }
        }

注意他 ref string---据我所知首先string 是引用类型,本身是按引用传递的~~那为什么他么这样写那
-------------------
于是我做了测试

   public static void s(String s)
       {
           Console.Write(s);
       }

     public static void s1(ref String s)
       {
           Console.WriteLine(s);
      
       }

.method public hidebysig static void  s1(string& s) cil managed
{
  // 代码大小       10 (0xa)
  .maxstack  8
  IL_0000:  nop
  IL_0001:  ldarg.0
  IL_0002:  ldind.ref=Loads an object reference as a type O (object reference) onto the evaluation stack indirectly
//--加载一个对象的引用他的类型被看作是跟0一样的 这个类型(对象引用) 在 这个堆栈上
  IL_0003:  call       void [mscorlib]System.Console::WriteLine(string)
  IL_0008:  nop
  IL_0009:  ret
} // end of method MyProcessClass::s1
- -这样多做一步对引用类型来说没什么好处哈哈..我估计这里写错了呵呵
--在做压力测试的时候-两种写发所用时间相同- -0

----------------------------于是我对值类型的又测试了下

 public static void s123(cc1 c)
       {

           Console.WriteLine(c.c);
       }

.method public hidebysig static void  s123(valuetype Process_Sample.MyProcessClass/cc1 c) cil managed
{
  // 代码大小       15 (0xf)
  .maxstack  8
  IL_0000:  nop
  IL_0001:  ldarga.s   c =Load an argument address, in short form, onto the evaluation stack.
                                  ldarga.s xx，即，读出参数xx的地址并压栈

 IL_0003:  ldfld      int32 Process_Sample.MyProcessClass/cc1::c
  IL_0008:  call       void [mscorlib]System.Console::WriteLine(int32)
  IL_000d:  nop
  IL_000e:  ret
} // end of method MyProcessClass::s123

 public static void s1234(ref cc1 c)
       {

           Console.WriteLine(c.c);
       }

  s123(c22);
      
  IL_0033:  ldloc.2//--ldloc.2=Loads the local variable at index 2 onto the evaluation stack.
//--加载变量
  IL_0034:  call       void Process_Sample.MyProcessClass::s123(valuetype Process_Sample.MyProcessClass/cc1)
  IL_0039:  nop

    s1234(ref c22);

  IL_003a:  ldloca.s   c22 //--ldloca.s=Loads the address of the local variable at a specific index onto the evaluation stack, short form.--加载地址
  IL_003c:  call       void Process_Sample.MyProcessClass::s1234(valuetype Process_Sample.MyProcessClass/cc1&)
  IL_0041:  nop