引用类型参数传递测试

引用类型参数传递测试（内容主要来自MSDN)

更详细的说明请参照MSDN"传递参数"

1.通过值传递引用类型
    例如传递数组change(string[] str),这种方式可以改变数组的值，相当于使用了ref,但是它和ref还是有区别的,这时如果使用new重新定义数组的维数，则改变是local的，不会影响到函数change以外的str
2.通过引用传递引用类型
    这种传递是明确使用ref,例如change(ref string[] str),这种方式和上面唯一的区别在于即使在函数内使用new重新定义数组也会影响到被引用的原始值,也就是change以外的str也随着change的改变而改变，是绝对的指针引用方式

以下是我的总结
-------------------------
3.对象是通过引用传递的,相当于前面使用ref
4.你可以在对象引用前加ref,这种调用和3的结果是一样的
5.对结构类型的参数是通过值传递的,函数内的改变不会影响函数外的原始值
6.接口相当于对象也是通过引用传递的,他的情况和3完全相同

具体测试代码如下:
-------------------------
using System;
using System.Data;
using System.Data.SqlClient;

namespace ConsoleApplication1
{
 class Class1
 {
  [STAThread]
  static void Main(string[] args)
  {
   //1.通过值传递引用类型
   Console.WriteLine("1.通过值传递引用类型");
   TestValueRef tvr = new TestValueRef();
   tvr.Test();

   //2.通过引用传递引用类型
   Console.WriteLine("2.通过引用传递引用类型");
   TestValueRefByRef tvrbr = new TestValueRefByRef();
   tvrbr.Test();

   //3.交换字符串

   //4.测试传递对象是否是引用类型
   Console.WriteLine("4.测试传递对象是否是引用类型");
   TestTest2 t = new TestTest2();
   t.Test();
   
   //5.测试传递结构是否是引用类型
   Console.WriteLine("5.测试传递结构是否是引用类型");
   TestStruct testStruct = new TestStruct();
   testStruct.Test();

   //6.测试传递接口是否是引用类型
   Console.WriteLine("6.测试传递接口是否是引用类型");
   TestInterface testInterface = new TestInterface();
   testInterface.Test();

   Console.Read();
  }
 }
 class TestValueRef
 {
  public void Test()
  {
   string[] str = new string[5]{"1","2","3","4","5"};
   print(str,"原始数据");
   change(str);
   print(str,"更改结束");
  }
  private void change(string[] str)
  {
   str[0] = "333";
   print(str,"更改数组的一个值");
   str = new string[6]{"0","1","2","3","4","5"};
   print(str,"更改函数内改变数组的维数");
  }
  private void print(string[] str,string strMsg)
  {
   Console.WriteLine();
   Console.WriteLine(strMsg);
   foreach (string s in str)
   {
    Console.WriteLine(s);
   }
  }
 }

 class TestValueRefByRef
 {
  public void Test()
  {
   string[] str = new string[5]{"1","2","3","4","5"};
   print(str,"原始数据");
   change(ref str);
   print(str,"更改结束");
  }
  private void change(ref string[] str)
  {
   str[0] = "333";
   print(str,"更改数组的一个值");
   str = new string[6]{"0","1","2","3","4","5"};
   print(str,"更改函数内改变数组的维数");
  }
  private void print(string[] str,string strMsg)
  {
   Console.WriteLine();
   Console.WriteLine(strMsg);
   foreach (string s in str)
   {
    Console.WriteLine(s);
   }
  }
 }
 class TestObjectRef
 {
  public string strTest = "this is a test";
 }
 class TestTest2
 {
  public void Test()
  {
   TestObjectRef o = new TestObjectRef();
   Console.WriteLine(o.strTest);
   Change(ref o);
   Console.WriteLine(o.strTest);
  }
  public void Change(ref TestObjectRef o)
  {
   o.strTest = "change object";
   Console.WriteLine(o.strTest);
  }
 }
 struct MyStruct
 {
  public string str1;
  public string str2;
  public string str3;
 }
 class TestStruct
 {
  public void Test()
  {
   MyStruct myStruct = new MyStruct();
   myStruct.str1 = "str1";
   myStruct.str2 = "str2";
   myStruct.str3 = "str3";
   print(myStruct,"更改前");
   Change(myStruct);
   print(myStruct,"更改后");
  }
  public void Change(MyStruct myStruct)
  {
   myStruct.str1 = "change1";
   myStruct.str2 = "change2";
   myStruct.str3 = "Change3";
   print(myStruct,"更改中");
  }
  public void print(MyStruct myStruct,string strMsg)
  {
   Console.WriteLine();
   Console.WriteLine(strMsg);
   Console.WriteLine(myStruct.str1);
   Console.WriteLine(myStruct.str2);
   Console.WriteLine(myStruct.str3);
  }
 }
 class TestInterface
 {
  public  void Test()
  {
   SqlCommand cmd =new SqlCommand();
   cmd.CommandText = "test";
   Console.WriteLine(cmd.CommandText);
   IDbCommand Icmd = (IDbCommand)cmd;
   Change(Icmd);
   Console.WriteLine(cmd.CommandText);
  }
  public void Change(IDbCommand iDb)
  {
   iDb.CommandText = "change";
   Console.WriteLine(iDb.CommandText);
  }
 }
}