How to: Perform Lazy Initialization of Objects

The xref:System.Lazy%601?displayProperty=nameWithType class simplifies the work of performing lazy initialization and instantiation of objects. By initializing objects in a lazy manner, you can avoid having to create them at all if they are never needed, or you can postpone their initialization until they are first accessed. For more information, see Lazy Initialization.

Example

The following example shows how to initialize a value with xref:System.Lazy%601. Assume that the lazy variable might not be needed, depending on some other code that sets the someCondition variable to true or false.

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");  
      }  
}

Example

The following example shows how to use the xref:System.Threading.ThreadLocal%601?displayProperty=nameWithType class to initialize a type that is visible only to the current object instance on the current thread.

[!code-csharpCDS#13] [!code-vbCDS#13]

dotnet/docs

How to: Perform Lazy Initialization of Objects

Example

Example

See Also