使用對象初始值設(shè)定項初始化對象
可以使用對象初始值設(shè)定項以聲明方式初始化類型對象，而無需顯式調(diào)用類型的構(gòu)造函數(shù)。
下面的示例演示如何將對象初始值設(shè)定項用于命名對象。編譯器通過先訪問默認(rèn)實例構(gòu)造函數(shù)然后處理成員初始化處理對象初始值設(shè)定項。因此，如果默認(rèn)構(gòu)造函數(shù)在類中聲明為 private，那么需要公共訪問權(quán)的對象初始值設(shè)定項將失敗。
下面的示例演示如何使用對象初始值設(shè)定項初始化新的 StudentName 類型。
public class Program{ public static void Main() { // Declare a StudentName by using the constructor that has two parameters. StudentName student1 = new StudentName("Craig", "Playstead"); // Make the same declaration by using an object initializer and sending // arguments for the first and last names. The default constructor is // invoked in processing this declaration, not the constructor that has // two parameters. StudentName student2 = new StudentName { FirstName = "Craig", LastName = "Playstead", }; // Declare a StudentName by using an object initializer and sending // an argument for only the ID property. No corresponding constructor is // necessary. Only the default constructor is used to process object // initializers. StudentName student3 = new StudentName { ID = 183 }; // Declare a StudentName by using an object initializer and sending // arguments for all three properties. No corresponding constructor is // defined in the class. StudentName student4 = new StudentName { FirstName = "Craig", LastName = "Playstead", ID = 116 }; System.Console.WriteLine(student1.ToString()); System.Console.WriteLine(student2.ToString()); System.Console.WriteLine(student3.ToString()); System.Console.WriteLine(student4.ToString()); }} 這段的輸出是：
Craig 0Craig 0183Craig 116
public class StudentName{ // The default constructor has no parameters. The default constructor // is invoked in the processing of object initializers. // You can test this by changing the access modifier from public to // private. The declarations in Main that use object initializers will // fail. public StudentName() { } // The following constructor has parameters for two of the three // properties. public StudentName(string first, string last) { FirstName = first; LastName = last; } // Properties. public string FirstName { get; set; } public string LastName { get; set; } public int ID { get; set; } public override string ToString() { return FirstName + " " + ID; }} 下面的示例演示如何使用集合初始值設(shè)定項初始化一個 StudentName 類型集合。請注意，集合初始值設(shè)定項是一系列由逗號分隔的對象初始值設(shè)定項。
List<StudentName> students = new List<StudentName>(){ new StudentName {FirstName="Craig", LastName="Playstead", ID=116}, new StudentName {FirstName="Shu", LastName="Ito", ID=112}, new StudentName {FirstName="Gretchen", LastName="Rivas", ID=113}, new StudentName {FirstName="Rajesh", LastName="Rotti", ID=114}};
使用集合初始值設(shè)定項初始化字典
Dictionary<TKey, TValue> 包含鍵/值對集合。 它的 Add 方法采用兩個參數(shù)，一個用于鍵，另一個用于值。 若要初始化 Dictionary<TKey, TValue> 或其 Add 方法采用多個參數(shù)的任何集合，請將每組參數(shù)括在大括號中，如下面的示例所示。
示例
在下面的代碼示例中，使用 StudentName 類型的實例初始化一個 Dictionary<TKey, TValue>。
class StudentName{ public string FirstName { get; set; } public string LastName { get; set; } public int ID { get; set; }}class CollInit{ Dictionary<int, StudentName> students = new Dictionary<int, StudentName>() { { 111, new StudentName {FirstName="Sachin", LastName="Karnik", ID=211}}, { 112, new StudentName {FirstName="Dina", LastName="Salimzianova", ID=317}}, { 113, new StudentName {FirstName="Andy", LastName="Ruth", ID=198}} };} 請注意集合的每個元素中的兩對大括號。 最內(nèi)層的大括號括起了 StudentName 的對象初始值，而最外層的大括號括起了將要添加到 studentsDictionary<TKey, TValue> 中的鍵/值對的初始值。 最后，字典的整個集合初始值括在一對大括號內(nèi)。
