C#3.0中自動(dòng)屬性和對(duì)象初始化器
作者：藍(lán)之風(fēng)
C#3.0中定義屬性更加方便，不用再在像之前的版本那樣的繁瑣，需要先定義存儲(chǔ)數(shù)據(jù)的字段，然后再定義屬性器，現(xiàn)在只需要定義屬性器就可以了,其它有編譯器自動(dòng)為我們完成，就可以省去定義字段時(shí)需要的那些時(shí)間；在對(duì)象初始化的時(shí)候我們可在對(duì)象構(gòu)造時(shí)實(shí)現(xiàn)對(duì)象屬性的初始化工作，和集合初始化類(lèi)似。
1.匿名屬性
定義屬性如下：
public class Employee
{
public int Id { get; set; }
public string Name { get; set; }
public string Sex { get; set; }
public int Age { get; set; }
public string BirthDate { get; set; }
}
在C#3.0 之前的寫(xiě)法如下：
public class Employee
{
private int _id;
private string _name;
private string _sex;
private int _age;
private string _birthDate;public int Id
{
get { return _id; }
set { _id = value; }
}
public string Name
{
get { return _name; }
set { _name = value; }
}
public string Sex
{
get { return _sex; }
set { _sex = value; }
}
public int Age
{
get { return _age; }
set { _age = value; }
}
public string BirthDate
{
get { return _birthDate; }
set { _birthDate = value; }
}
}
僅從代碼量上就前者比后者減少了2/3的代碼，這對(duì)提高效率是顯而易見(jiàn)的，那么這些代碼都到哪里去了呢？其實(shí)那些額外的代碼都是由編譯器為我們完成的，編譯器會(huì)將那些我們“省去"的代碼編譯成托管IL代碼的時(shí)候補(bǔ)進(jìn)去，兩者中代碼在最終生成的IL代碼的體積是差不多的。
上圖中的IL代碼中我們看到了
2.對(duì)象初始化器，原來(lái)的對(duì)象初始化都要進(jìn)行先創(chuàng)建構(gòu)造方法，然后才能進(jìn)行成員的相關(guān)操作，C#3.0 提供了對(duì)象成員的直接初始化的能力，和初始化一個(gè)集合或者是數(shù)組一樣來(lái)初始化對(duì)象。
相面來(lái)看，通過(guò)對(duì)象初始化器對(duì)上面的的Employee類(lèi)進(jìn)行進(jìn)行調(diào)用：
Employee employee = new Employee { Id = 1, Name = "藍(lán)之風(fēng)", Age = 24, BirthDate = "1984-10-21", Sex = "男" }; BirthDate = "1984-10-21", Sex = "男" }; |
就是對(duì)象的初始化，看到代碼很簡(jiǎn)潔，輸出的結(jié)果如下：
在C#3.0之前的做法是：
Employee employee = new Employee(); |
或者通過(guò)重載構(gòu)造方法的方式來(lái)初始化這些屬性，二者的達(dá)到的效果是相同的，但是前者使用起來(lái)方便了些，代碼量減少了許多，這個(gè)過(guò)程是怎么完成的呢？其實(shí)C#本身并沒(méi)有太大的變化，這些都是在語(yǔ)法上的一些改變，使得編寫(xiě)代碼的時(shí)候更方便效率更高，把一些編譯器可以推斷出來(lái)完成的工作讓編譯器來(lái)做了，編譯器在編譯程序的時(shí)候?qū)⑽覀儧](méi)有實(shí)現(xiàn)的代碼替我們實(shí)現(xiàn)來(lái)生成IL代碼的：
method private hidebysig static void Main(string[] args) cil managed
{
.entrypoint
// 代碼大小 175 (0xaf)
.maxstack 2
.locals init ([0] class CS30.Employee employee,
[1] class CS30.Employee '<>g__initLocal0')
IL_0000: nop
IL_0001: newobj instance void CS30.Employee::.ctor()
IL_0006: stloc.1
IL_0007: ldloc.1
IL_0008: ldc.i4.1
IL_0009: callvirt instance void CS30.Employee::set_Id(int32)
IL_000e: nop
IL_000f: ldloc.1
IL_0010: ldstr bytearray (DD 84 4B 4E CE 98 ) // ..KN..
IL_0015: callvirt instance void CS30.Employee::set_Name(string)
IL_001a: nop
IL_001b: ldloc.1
IL_001c: ldc.i4.s 24
IL_001e: callvirt instance void CS30.Employee::set_Age(int32)
IL_0023: nop
IL_0024: ldloc.1
IL_0025: ldstr "1984-10-21"
IL_002a: callvirt instance void CS30.Employee::set_BirthDate(string)
IL_002f: nop
IL_0030: ldloc.1
IL_0031: ldstr bytearray (37 75 ) // 7u
IL_0036: callvirt instance void CS30.Employee::set_Sex(string)
IL_003b: nop
IL_003c: ldloc.1
IL_003d: stloc.0
IL_003e: ldstr bytearray (16 7F F7 53 3B 00 7B 00 30 00 7D 00 ) // ...S;.{.0.}.
IL_0043: ldloc.0
IL_0044: callvirt instance int32 CS30.Employee::get_Id()
IL_0049: box [mscorlib]System.Int32
IL_004e: call void [mscorlib]System.Console::WriteLine(string,
object)
IL_0053: nop
IL_0054: ldstr bytearray (D3 59 0D 54 3A 00 7B 00 30 00 7D 00 ) // .Y.T:.{.0.}.
IL_0059: ldloc.0
IL_005a: callvirt instance string CS30.Employee::get_Name()
IL_005f: call void [mscorlib]System.Console::WriteLine(string,
object)
IL_0064: nop
IL_0065: ldstr bytearray (74 5E 84 9F 3A 00 7B 00 30 00 7D 00 ) // t^..:.{.0.}.
IL_006a: ldloc.0
IL_006b: callvirt instance int32 CS30.Employee::get_Age()
IL_0070: box [mscorlib]System.Int32
IL_0075: call void [mscorlib]System.Console::WriteLine(string,
object)
IL_007a: nop
IL_007b: ldstr bytearray (1F 75 E5 65 3A 00 7B 00 30 00 7D 00 ) // .u.e:.{.0.}.
IL_0080: ldloc.0
IL_0081: callvirt instance string CS30.Employee::get_BirthDate()
IL_0086: call void [mscorlib]System.Console::WriteLine(string,
object)
IL_008b: nop
IL_008c: ldstr bytearray (27 60 2B 52 3A 00 7B 00 30 00 7D 00 ) // '`+R:.{.0.}.
IL_0091: ldloc.0
IL_0092: callvirt instance string CS30.Employee::get_Sex()
IL_0097: call void [mscorlib]System.Console::WriteLine(string,
object)
IL_009c: nop
IL_009d: ldstr bytearray (F7 8B 09 63 FB 4E 0F 61 2E 95 E7 7E ED 7E 2E 00 // ...c.N.a...~.~..
2E 00 2E 00 ) // ....
IL_00a2: call void [mscorlib]System.Console::WriteLine(string)
IL_00a7: nop
IL_00a8: call string [mscorlib]System.Console::ReadLine()
IL_00ad: pop
IL_00ae: ret
} // end of method Program::Main【編輯推薦】
責(zé)任編輯：彭凡
來(lái)源：
cnblogs
