该 System.Lazy<T> 类简化了执行延迟初始化和实例化对象的工作。 通过延迟初始化对象，可以避免在不需要时创建它们，或者可以推迟其初始化，直到首次访问它们。 有关详细信息，请参阅 延迟初始化。
Example 1
以下示例演示如何使用 Lazy<T>. 初始化值。 假设可能并不需要这个惰性变量，这取决于某些其他代码是否将变量设置为someCondition、true或false。
Dim someCondition As Boolean = False
Sub Main()
'Initialize 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 might or might 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;
// Initialize 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);
}, LazyThreadSafetyMode.ExecutionAndPublication);
// Do some work that might or might not set someCondition to true...
// Initialize the data only if necessary.
if (someCondition)
{
if (_data.Value > 100)
{
Console.WriteLine("Good data");
}
}
Example 2
以下示例演示如何使用 System.Threading.ThreadLocal<T> 类初始化仅对当前线程上的当前对象实例可见的类型。
// Initialize a value per thread, per instance.
ThreadLocal<int[][]> _scratchArrays =
new(InitializeArrays);
static int[][] InitializeArrays() => [new int[10], new int[10]];
// Use the thread-local data.
int i = 8;
int[] tempArr = _scratchArrays.Value[i];
'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
