1. 禁止在一個類的靜態構造函數中訪問另一個類中的靜態成員。
猜下下面這段程序的輸出結果：
using System;using System.Threading;namespace TypeConstructorLock
{
class Class1
{
[STAThread] public static void Main(string[] args) { Thread threadA = new Thread(new ThreadStart(TouchStatic1)); threadA.Name = "Thread A"; Thread threadB = new Thread(new ThreadStart(TouchStatic2)); threadB.Name = "Thread B"; threadA.Start(); threadB.Start(); threadA.Join(); threadB.Join();
} static void TouchStatic1() { string s = Static1.Message; } static void TouchStatic2() { string s = Static2.Message; } } class Static1 { static Static1() { Console.WriteLine("Begin Static1 .cctor on thread {0}", Thread.CurrentThread.Name); Thread.Sleep(5000); Console.WriteLine("//Static1 has a message from Static2: {0}", Static2.Message); message = "Hello From Static1"; Console.WriteLine("Exit Static1 .cctor on thread {0}", Thread.CurrentThread.Name); } static public string Message { get { return message; } } static string message = "blank"; } class Static2 { static Static2() { Console.WriteLine("Begin Static2 .cctor on thread {0}", Thread.CurrentThread.Name); Thread.Sleep(5000); Console.WriteLine("//Static2 has a message from Static1: {0}", Static1.Message); message = "Hello From Static2"; Console.WriteLine("Exit Static2 .cctor on thread {0}", Thread.CurrentThread.Name); } static public string Message { get { return message; } } static string message = "blank"; }
}執行結果：
E:CSC>staticlock.exeBegin Static1 .cctor on thread Thread ABegin Static2 .cctor on thread Thread B//Static2 has a message from Static1: blankExit Static2 .cctor on thread Thread B//Static1 has a message from Static2: Hello From Static2Exit Static1 .cctor on thread Thread A
留意上面的“//static2 has a message from static1:black”，里面取得的字符串值是“blank”，而不是“Hello From Static1”，我們不能確定兩個靜態構造函數中的兩條message賦值語句誰已經執行或沒有執行! 這里要記住一條規則：禁止在一個類的靜態構造函數中訪問另一個類中的靜態成員(Avoid touching the static members of another type from within a type constructor)。雖然我們很少情況下會寫出上面這種代碼，但一旦寫出來了，這種錯誤將很難調試，我們要牢記這樣準則。
2. 如果靜態構造函數中有異常(用E描述)拋出，則CLR會對E進行包裝，重新拋出一個System.TypeInitializationException異常，而把E作為該異常的InnerException。在進行程序設計時，我們一定要保證在類的靜態構造函數不能有異常拋出!
3. C#中不支持子類繼承父類的靜態成員，但卻可以通過子類類名來訪問父類的靜態成員!
反射靜態成員的示例：
using System;using System.Reflection;namespace Reflection{ class Class1 { [STAThread] static void Main(string[] args) { Type type; object result; PropertyInfo[] properties; object instance = null; object[] index = null; type = typeof(Static1); properties = type.GetProperties(BindingFlags.Static | BindingFlags.Public); result = properties[0].GetValue(instance, index);//注意：訪問內的靜態成員，這里傳入的是null Console.WriteLine(result.ToString()); type = typeof(Static2); properties = type.GetProperties(BindingFlags.Static | BindingFlags.Public | BindingFlags.FlattenHierarchy);//如果不運用FlattenHierarchy，則返回空數組。 /*FlattenHierarchy：指定應返回層次結構上的公共靜態成員和受保護的靜態成員。 * 不返回繼承類中的私有靜態成員。靜態成員包括字段、方法、事件和屬性。不返回嵌套類型。 * * FlattenHierarchy告訴CLR將基類Static1的靜態屬性也算在內！ * C#中不支持子類繼承父類的靜態成員，但卻可以通過子類類名來訪問父類的靜態成員！ * e.g.:我們可以通過訪問Static2.Message來訪問Static1.Message * */ result = properties[0].GetValue(instance, index); Console.WriteLine(result.ToString()); Console.WriteLine(Static2.Message); } } class Static1 { static public string Message { get { return message; } } static string message = "Hello World 1"; } class Static2 : Static1{}}執行結果：
E:CSC>refstatic.exeHello World 1Hello World 1
參考：http://msdn.microsoft.com/msdnmag/issues/05/01/StaticsinNET/default.aspx
浙公網安備 33010602011771號