What Does the `=>` Syntax Mean in C#?

Deeply explore the mysterious '=>' syntax in C#

Have you ever encountered the mysterious '=>' syntax in C# code and wondered what it means? Let’s demystify it and explore its diverse uses.

This convoluted notation, called the lambda operator, has been an integral part of the C# language since version 3.0. Originally used in lambda expressions, it provides a neat alternative to anonymous methods. These expressions provide a compact way to define a function without explicitly declaring its full signature.

For example, the following code creates a lambda expression using the '=>' syntax:

<code class="language-c#">Func<Person, string> nameProjection = p => p.Name;</code>

This expression is equivalent to the following anonymous method:

<code class="language-c#">Func<Person, string> nameProjection = delegate (Person p) { return p.Name; };</code>

In both cases, the delegate accepts a Person as parameter and returns its Name property as a string.

However, the '=>' syntax really shines in C# 6 and above. It is used for expression body members, greatly simplifying your code by allowing you to define properties and methods using concise expressions.

Consider the following example:

<code class="language-c#">// 表达式主体属性
public int IsValid => name != null && id != -1;

// 表达式主体方法
public int GetHashCode() => id.GetHashCode();</code>

These expressions provide a more concise way to define the behavior of properties and methods without lengthy blocks of code.

To further expand your knowledge, please refer to the following resources:

• Difference between anonymous methods (C# 2.0) and lambda expressions (C# 3.0)
• What is Lambda?
• C# Lambda expression, why should I use it?

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