System.Lazy<T> 类简化了执行对象的延迟初始化和实例化的工作。 通过以延迟方式实例化对象，可避免在根本不需要的情况下必须创建所有的对象，或者可以将对象的初始化延迟到第一次访问它们的时候。 有关更多信息，请参见延迟初始化。
示例
下面的示例演示如何使用 Lazy<T> 初始化值。 假定延迟变量可能不是必需的，具体取决于将 someCondition 变量设置为 true 或 false 的一些其他代码。
Dim someCondition As Boolean = False
Sub Main()
'Initializing a value with a big computation, computed in parallel
Dim _data As Lazy(Of Integer) = New Lazy(Of Integer)(Function()
Dim result =
ParallelEnumerable.Range(0, 1000).
Aggregate(Function(x, y)
Return x + y
End Function)
Return result
End Function)
' do work that may or may not set someCondition to True
' ...
' Initialize the data only if needed
If someCondition = True Then
If (_data.Value > 100) Then
Console.WriteLine("Good data")
End If
End If
End Sub
static bool someCondition = false;
//Initializing a value with a big computation, computed in parallel
Lazy<int> _data = new Lazy<int>(delegate
{
return ParallelEnumerable.Range(0, 1000).
Select(i => Compute(i)).Aggregate((x,y) => x + y);
}, LazyExecutionMode.EnsureSingleThreadSafeExecution);
// Do some work that may or may not set someCondition to true.
// ...
// Initialize the data only if necessary
if (someCondition)
{
if (_data.Value > 100)
{
Console.WriteLine("Good data");
}
}
下面的示例演示如何使用 System.Threading.ThreadLocal<T> 类来初始化仅对当前线程上的当前对象实例可见的类型。
'Initializing a value per thread, per instance
Dim _scratchArrays =
New ThreadLocal(Of Integer()())(Function() InitializeArrays())
' use the thread-local data
Dim tempArr As Integer() = _scratchArrays.Value(i)
' ...
End Sub
Function InitializeArrays() As Integer()()
Dim result(10)() As Integer
' Initialize the arrays on the current thread.
' ...
Return result
End Function
//Initializing a value per thread, per instance
ThreadLocal<int[][]> _scratchArrays =
new ThreadLocal<int[][]>(InitializeArrays);
// . . .
static int[][] InitializeArrays () {return new int[][]}
// . . .
// use the thread-local data
int i = 8;
int [] tempArr = _scratchArrays.Value[i];
请参见
参考
System.Threading.LazyInitializer