Lazy<T> is a powerful feature in the .NET Framework that allows you to defer the creation of an object until it’s actually needed. This can be incredibly useful when working with large or expensive objects, as it allows you to avoid the performance overhead of creating the object until it’s actually needed. In this post, we’ll take a look at how to use Lazy<T> in C# and explore some of the pros and pitfalls to watch out for.

Creating a Lazy<T> object

Creating a Lazy<T> object is very simple in C#. To create a new instance of a Lazy<T> object, you simply need to provide a delegate that will be used to create the object when it’s needed. Here’s an example:

Lazy<string> lazyString = new Lazy<string>(() => "Hello, World!");

In this example, we’re creating a new Lazy<string> object and providing a lambda expression that will be used to create the string “Hello, World!” when the object is accessed for the first time.

Accessing the Lazy<T> object

Accessing the Lazy<T> object is just as simple as creating it. When you first access the object, the delegate you provided when creating the object will be executed to create the actual object. Here’s an example of accessing the lazyString object we created in the previous example:

string greeting = lazyString.Value;
Console.WriteLine(greeting); // Output: "Hello, World!"

In this example, we’re accessing the Value property of the lazyString object, which will execute the delegate we provided when creating the object and return the resulting string.

Pros of using Lazy<T>

There are several advantages to using Lazy<T> in your code:

Improved performance

One of the biggest advantages of using Lazy<T> is that it can help improve the performance of your code. By deferring the creation of an object until it’s actually needed, you can avoid the performance overhead of creating the object prematurely.

Reduced memory usage

Lazy<T> can also help reduce memory usage in your application. If you have an object that’s only used occasionally, you can use Lazy<T> to avoid creating the object until it’s actually needed. This can help reduce the overall memory usage of your application.

Simplified code

Using Lazy<T> can also simplify your code. Instead of having to manually check whether an object has been created and create it if it hasn’t, you can simply create a Lazy<T> object and access its Value property when you need the object.

Pitfalls to watch out for

While Lazy<T> can be a powerful tool in your programming arsenal, there are some pitfalls to watch out for:

Thread safety

By default, Lazy<T> is not thread-safe. If you’re using Lazy<T> in a multi-threaded application, you’ll need to take steps to ensure that the object is created only once and that all threads have access to the same object.

Overhead

Using Lazy<T> can introduce some overhead into your code. If you’re creating a large number of Lazy<T> objects, this overhead can start to add up and impact the overall performance of your application.

Exceptions

If the delegate you provide to Lazy<T> throws an exception, the exception will be thrown the first time the Value property is accessed. This can make it difficult to handle exceptions that occur during object creation.

In sum, Lazy<T> is a powerful feature in the .NET Framework that can help improve the performance and memory usage of your applications.