The document discusses the Generic Lazy class introduced in .NET Framework 4.0, which provides support for lazy initialization. It inherits from System.Lazy<T> and is defined in the System namespace in mscorlib.dll. The Lazy<T> class has properties and constructors for lazy initialization, deferring the initialization of an object until its value is accessed. An example demonstrates initializing an int array lazily, only creating it when the Value property is first accessed.

1. GENERIC LAZY CLASS
Larry Nung

2. AGENDA
Generic Lazy class
Reference
Q & A
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3. GENERIC LAZY CLASS
 .NET Framework 4.0+
 Provides support for lazy initialization.
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4. BASIC CONCEPT
public class Lazy<T> {
private Func<T> func;
private T result;
private bool hasValue;
public Lazy(Func<T> func) {
this.func = func;
this.hasValue = false;
}
public T Value {
get {
if (!this.hasValue) {
this.result = this.func();
this.hasValue = true;
}
return this.result;
}
}
}
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5. INHERITANCE
HIERARCHY/NAMESPACE/ASSEMBLY
Inheritance Hierarchy
System.Object
System.Lazy<T>
System.Lazy<T, TMetadata>
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
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6. SYNTAX
[SerializableAttribute]
[ComVisibleAttribute(false)]
[HostProtectionAttribute(SecurityAction.LinkDemand,
Synchronization = true, ExternalThreading = true)]
public class Lazy<T>
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7. CONSTRUCTORS
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8. PROPERTIES
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9. EXAMPLE
static Lazy<int[]> _stocks = new Lazy<int[]>(() =>
{
//Initializing...
return new int[] { 2002, 2360, 0050 };
});
private static int[] m_Stocks {
get { return _stocks.Value; }
}
static void Main(string[] args) {
Console.WriteLine(string.Join(",", m_Stocks.Select((value) => {
return value.ToString();
})));
} 9

10. EXAMPLE
var lazy = new Lazy<Boolean>(() => {
Console.WriteLine("Initializing...");
System.Threading.Thread.Sleep(10000);
Console.WriteLine("Initialized...");
return true;
});
Console.WriteLine("IsValueCreated = {0}", lazy.IsValueCreated);
var sw = Stopwatch.StartNew();
Console.WriteLine("result = {0}", lazy.Value);
//Console.WriteLine("result = {0}", lazy.ToString());
Console.WriteLine("Elapsed Time = {0} ms", sw.ElapsedMilliseconds);
Console.WriteLine(new string('=', 50));
Console.WriteLine("IsValueCreated = {0}", lazy.IsValueCreated);
sw.Restart();
Console.WriteLine("result = {0}", lazy.Value);
//Console.WriteLine("result = {0}", lazy.ToString());
Console.WriteLine("Elapsed Time = {0} ms", sw.ElapsedMilliseconds);
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11. REFERENCE
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12. REFERENCE
 Lazy(T) 類別 (System)
 https://msdn.microsoft.com/zh-tw/library/dd642331.aspx
 .NET 4.0 New Feature - Generic Lazy class | Level Up -
點部落
 https://www.dotblogs.com.tw/larrynung/archive/2010/11/07/188
60.aspx
 [C#]LevelUp.Lazy | Level Up - 點部落
 https://www.dotblogs.com.tw/larrynung/2011/04/03/22246
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13. Q&A
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14. QUESTION & ANSWER
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