C# Member Variable Initialization: Declaration vs. Constructor – Which is Best?

C# best practices for member variable initialization

When declaring class member variables in C#, you can choose to initialize them at declaration time or initialize them in the default constructor. Although both methods initialize variables, there are subtle differences and advantages and disadvantages between them.

Performance impact

In terms of performance, there is no significant difference between initializing a variable at declaration time and initializing it in the constructor. In both cases, the value is assigned during object instantiation.

Grammar considerations

Initializing variables directly at declaration time allows for a concise and localized way of keeping relevant variables and their values ​​in the class definition. However, this method does not support automatically implemented properties.

Constructor-based initialization

Constructor-based initialization provides flexibility for more complex scenarios. It allows:

• Customized initialization logic based on constructor parameters
• Handle situations where multiple constructors exist and fields must be initialized consistently

Personal Preference

The preferred method often comes down to personal style and code readability. Some developers prefer the clarity and simplicity of initializing variables directly at declaration time. Others may prefer constructor-based initialization for its flexibility and consistency across multiple constructors.

Example

Here are examples of both methods:

When declaring:

<code class="language-csharp">private readonly List<SomeClass> items = new List<SomeClass>();
public List<SomeClass> Items { get { return items; } }</code>

in constructor:

<code class="language-csharp">public Bar()
{
  // 自定义初始化逻辑
  Foo = "";
}</code>

Conclusion

Ultimately, best practices depend on specific needs and preferred coding style. Both approaches are valid, but understanding the nuances allows you to make an informed decision based on your project's needs.

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