如何：了解向方法传递结构和向方法传递类引用之间的区别（C# 编程指南）

本示例演示在向方法传递结构时，传递的是该结构的副本，而在传递类实例时，传递的是一个引用。

本示例的输出表明：当向 ClassTaker 方法传递类实例时，只更改类字段的值。但是向 StructTaker 方法传递结构实例并不更改结构字段。这是因为向 StructTaker 方法传递的是结构的副本，而向 ClassTaker 方法传递的是对类的引用。

示例

class TheClass
{
public string willIChange;
}

struct TheStruct
{
public string willIChange;
}

class TestClassAndStruct
{
static void ClassTaker(TheClass c)
{
c.willIChange = "Changed";
}

static void StructTaker(TheStruct s)
{
s.willIChange = "Changed";
}

static void Main()
{
TheClass testClass = new TheClass();
TheStruct testStruct = new TheStruct();

testClass.willIChange = "Not Changed";
testStruct.willIChange = "Not Changed";

ClassTaker(testClass);
StructTaker(testStruct);

Console.WriteLine("Class field = {0}", testClass.willIChange);
Console.WriteLine("Struct field = {0}", testStruct.willIChange);

// Keep the console window open in debug mode.
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
}
}
/* Output:
Class field = Changed
Struct field = Not Changed
*/