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

C# best practices for member variable initialization

When initializing class member variables in C#, developers often need to choose between declaring and initializing them or assigning values ​​in the default constructor. This article explores best practices for this decision, exploring potential performance implications and style preferences.

Performance considerations

In terms of performance, there is no significant difference between initializing member variables in the declaration versus initializing them in the constructor. Field initializers are actually implemented as constructor logic, executed before any "base" or "this" constructor calls.

Style and Convenience

Constructor methods allow initialization with automatically implemented properties, which is not possible with field initializers. However, many developers prefer field initializers because they allow localized property management and make it easy to find where variables are assigned values.

For example, consider the following code:

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

Using this approach, all assignments and getters are kept in one place, reducing the need to search for initialization elsewhere.

When to use constructor-based initialization

However, constructor-based initialization is required when performing complex logic or using constructor parameters. Additionally, when multiple constructors are present, it is best to use constructor-based initialization to ensure consistent initialization.

Note: Field initialization in constructor

It is important to note that when using multiple constructors, field initializers are only called directly in the constructor that calls the base constructor. Other constructors rely on the base constructor to handle field initialization.

Conclusion

While there is no performance trade-off, the choice between initializing member variables in a declaration versus initializing them in a constructor often comes down to style preference. Field initializers provide localized property management and easy access, while constructor-based initialization allows automated implementation and control of complex logic. Developers should choose the method that best suits their specific needs as well as code readability and maintainability.

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