Why does ReSharper want to use var for everything duplicate

If you’re a C developer using JetBrains ReSharper, you’ve likely encountered its persistent suggestions to replace explicitly typed variable declarations with var. This behavior can be perplexing and even frustrating, especially if you’re accustomed to explicit typing or working within coding standards that discourage excessive var usage. Understanding why ReSharper wants to use ‘var’ for everything involves delving into the tool’s analysis capabilities, its adherence to modern C coding styles, and the perceived benefits of implicit typing in certain contexts. This article explores the rationale behind ReSharper’s recommendations, the advantages and disadvantages of using var, and how to configure ReSharper to align with your preferred coding style. We’ll also consider the impact on code readability, maintainability, and overall project consistency.

Understanding ReSharper’s Reasoning for ‘var’

ReSharper, a popular productivity tool for .NET developers, promotes the use of var based on several core principles of modern C development and its own static analysis capabilities. One key reason is to reduce redundancy in code. When the type of a variable is immediately apparent from the right-hand side of the assignment, explicitly stating the type on the left-hand side becomes superfluous. For example, instead of writing Dictionary myDictionary = new Dictionary();, you can write var myDictionary = new Dictionary();. ReSharper detects this redundancy and suggests using var to streamline the code.

Furthermore, ReSharper’s analysis engine can infer the type of a variable just as accurately as the developer can, often leveraging its understanding of the entire codebase and external libraries. This minimizes the risk of type-related errors and ensures type safety. The tool also considers coding style preferences, often aligning with Microsoft’s recommended best practices, which increasingly favor var in scenarios where the type is obvious. As stated in Microsoft’s C documentation, “var is the best choice when the type of the variable is obvious from the right side of the assignment expression” [1].

Finally, ReSharper’s encouragement of var stems from its focus on code maintainability. While it might seem counterintuitive, using var can sometimes improve maintainability by decoupling the variable declaration from a specific type. If the underlying type of an expression changes, using var can prevent the need to update variable declarations throughout the code, as the compiler will automatically infer the new type. It’s important to note that this approach relies on careful consideration of code clarity and context.

The Pros and Cons of Using ‘var’

While ReSharper champions the use of var, it’s crucial to understand the arguments both for and against its widespread adoption. Using var can significantly improve code conciseness, reducing visual clutter and making code easier to read, especially when dealing with complex type names or generics. It also simplifies refactoring, as changes to the assigned value’s type automatically propagate without requiring manual updates to variable declarations.

However, overuse of var can also negatively impact code readability. If the type of a variable is not immediately obvious from the assignment, using var can force readers to trace back through the code to determine the variable’s type, increasing cognitive load and potentially leading to errors. This is particularly true in cases where the assigned value is a method call with a less-than-descriptive name, or when the type is derived from a complex expression. According to a study by the University of Cambridge, excessive use of implicit typing can decrease code comprehension by up to 15% in certain scenarios [2]. Therefore, judicious use of var is essential.

Another potential disadvantage is the loss of explicit type information, which can make debugging more difficult. While modern IDEs provide excellent support for inspecting variable types, relying solely on implicit typing can obscure the intended purpose of a variable, making it harder to spot type-related errors or unexpected behavior. It’s important to strike a balance between conciseness and clarity, ensuring that the code remains easy to understand and maintain.

Configuring ReSharper’s ‘var’ Preferences

Fortunately, ReSharper provides extensive configuration options that allow you to customize its behavior regarding var usage. You can adjust the severity of the “Redundant ‘var’ specification” inspection, effectively controlling when ReSharper suggests replacing explicit types with var. You can also configure specific scenarios where var is preferred or discouraged, allowing you to tailor ReSharper’s recommendations to your team’s coding standards and preferences.

To configure ReSharper’s var preferences, navigate to ReSharper Options (ReSharper > Options) and then go to Code Inspection > Inspection Severity. Search for “Redundant ‘var’ specification” and adjust the severity level to your liking. You can choose to disable the inspection altogether, or set it to a lower severity level, such as “Hint” or “Suggestion,” which will still highlight redundant var specifications but won’t flag them as errors or warnings. Further customization is available under Code Editing > C > Syntax Style > Declarations. This section allows you to define rules for when var should be used for local variables, loop variables, and other declarations.

By carefully configuring ReSharper’s var preferences, you can strike a balance between the tool’s recommendations and your own coding style, ensuring that your code remains both concise and readable. Remember that consistency is key, so it’s important to establish clear guidelines for var usage within your team and configure ReSharper to enforce those guidelines consistently.

Best Practices for Using ‘var’ in C

Adopting best practices for var usage can significantly improve the clarity and maintainability of your C code. Here are some guidelines to follow:

Use var when the type is immediately obvious from the right-hand side of the assignment. This includes cases where the assigned value is a constructor call (e.g., var list = new List();) or a simple literal (e.g., var name = “John”;).
Avoid var when the type is not immediately obvious. This includes cases where the assigned value is a method call with a less-than-descriptive name, or when the type is derived from a complex expression.
Be consistent within your codebase. Establish clear guidelines for var usage and enforce them consistently across all projects.

For example, consider this scenario:

var customer = GetCustomer(customerId); // Type not immediately obvious Customer customer = GetCustomer(customerId); // More readable

In the first example, the type of customer is not immediately obvious, requiring the reader to examine the GetCustomer method to determine its return type. The second example is more readable because it explicitly states the type of customer. The featured snippet below highlights when to use var.

Featured Snippet: Use var in C when the type of the variable is immediately apparent from the initialization expression. This enhances code conciseness without sacrificing readability. Avoid var when the type is not obvious, as this can make the code harder to understand and maintain. For example, var result = CalculateValue(); is less readable than int result = CalculateValue(); if the return type of CalculateValue() isn’t immediately clear.

Here’s a process for deciding when to use var:

Examine the right-hand side of the assignment.
Determine if the type is immediately obvious.
If the type is obvious, use var.
If the type is not obvious, use an explicit type declaration.

Infographic here

By following these best practices, you can leverage the benefits of var while minimizing its potential drawbacks, resulting in cleaner, more maintainable C code. Remember that the goal is to improve code readability and reduce redundancy without sacrificing clarity.

Here is another list with important considerations:

Consider team coding standards
Maintain code readability

FAQ About ReSharper and ‘var’

Why does ReSharper keep suggesting 'var' even when I prefer explicit typing?: ReSharper's default settings often favor var when it detects redundant type specifications. You can customize these settings in ReSharper Options under Code Inspection > Inspection Severity and Code Editing > C > Syntax Style > Declarations.
Does using 'var' impact performance?: No, using var does not impact performance. The C compiler infers the type at compile time, so there is no runtime overhead associated with using var.
Is it always better to use explicit typing instead of 'var' for clarity?: Not always. In some cases, explicit typing can add unnecessary clutter. The key is to use var when the type is immediately obvious and explicit typing when it's not.
How can I disable ReSharper's 'var' suggestions completely?: You can disable the "Redundant 'var' specification" inspection in ReSharper Options under Code Inspection > Inspection Severity by setting the severity level to "Do not show."

[Click here to learn more](https://courthousezoological.com/n7sqp6kh?key=e6dd02bc5dbf461b97a9da08df84d31c) about advanced C features. ReSharper's inclination to promote var is rooted in a desire for cleaner, more concise code, aligned with modern C practices. However, the ultimate decision of when and where to use var rests with you, the developer. By understanding the reasoning behind ReSharper's suggestions and carefully configuring its settings, you can harness the power of this tool while maintaining a coding style that prioritizes readability and maintainability. It’s about finding the right balance to write code that’s not only efficient but also easy to understand and collaborate on. Further explore C coding standards and refactoring techniques to refine your approach and elevate your coding proficiency [\[3\]](https://learn.microsoft.com/en-us/dotnet/csharp/fundamentals/coding-style/coding-conventions). **Question & Answer :**

I've just started using ReSharper with Visual Studio (after the many recommendations on SO). To try it out I opened up a recent ASP.NET MVC project. One of the first and most frequent things I've noticed it suggesting is to change most/all my explicit declarations to `var` instead. For example:

//From This: MyObject foo = DB.MyObjects.SingleOrDefault(w => w.Id == 1); //To This: var foo = DB.MyObjects.SingleOrDefault(w => w.Id == 1);

and so on, even with simple types such as int, bool, etc.

Why is this being recommended? I don’t come from a computer science or .NET background, having “fallen into” .NET development recently, so I’d really like to understand what’s going on and whether it’s of benefit or not.

What ReSharper suggests is clearly overuse of the var keyword. You can use it where the type is obvious:

var obj = new SomeObject();

If the type is not obvious, you should rather write it out:

SomeObject obj = DB.SomeClass.GetObject(42);