Microsoft .NET Code Analysis: Validate Arguments of Public Methods

One issue I frequently encounter while reviewing code is the lack of argument validation in public methods. As a software engineer with over 20 years of experience, I find it puzzling why this problem persists. I have emphasized the importance of addressing this issue in my discussions and written materials for a considerable period. Failing to validate arguments can result in the introduction of erroneous data into the program’s structure, thus undermining the fundamental principle of Object-Oriented Programming, encapsulation.

To illustrate this problem, consider the following code snippet:

public async Task Invoke(HttpContext context)
{
	var id = context.Request.Headers["AppId"];

	// Code removed for brevity

}

In this particular example, it is advisable to incorporate exception handling, as the task at hand cannot be successfully executed. Here is an updated version of the code, including the appropriate exception handling:

public async Task Invoke(HttpContext context)
{
	if (context is null)
	{
		throw new ArgumentNullException(nameof(context), "HTTPContext cannot be null");
	}

	var id = context.Request.Headers["AppId"];

	// Code removed for brevity

}

Here are more reasons why arguments should always be validated:

1. NullReferenceException: If a null parameter is used without validation, it can lead to a NullReferenceException at runtime when the code attempts to access members or properties of the null object.
2. Unexpected behavior: Failing to validate parameters can result in unexpected behavior or incorrect results. For example, if a method expects a non-null collection as a parameter and it receives a null value, it may not behave as intended, leading to logical errors or data corruption.
3. Security vulnerabilities: Parameter validation is crucial for security. By not validating inputs, your code may be susceptible to attacks such as injection or privilege escalation. Proper validation helps ensure that the provided data meets the required criteria, preventing potential security vulnerabilities.
4. Maintenance and debugging difficulties: Neglecting parameter validation can make code maintenance and debugging more challenging. When parameters are not validated, it becomes harder to determine the source of errors or understand why certain values are causing issues.

Failure to validate arguments is a surefire way to introduce bugs into your project. To mitigate this risk, it is highly recommended to include the following setting in your EditorConfig file.

When I setup the CA1062 code analysis in my .editorConfig it looks like this: dotnet_diagnostic.CA1062.severity = error

Summary

While reviewing the codebase for this recommendation, I came across a concerning issue. I identified a total of 700 instances in their code where arguments were not being adequately validated. This is a significant number, and it reinforces the importance of the saying, “Bad Data In, Bad Data Out.” It is crucial to address these validation gaps to ensure the integrity and reliability of the system’s output.

For further guidance and insights, I highly recommend obtaining a copy of my book, “Rock Your Code: Coding Standards for Microsoft .NET” available on Amazon.com. Additionally, to explore more performance tips for .NET, I encourage you to acquire the 3rd edition of “Rock Your Code: Code & App Performance for Microsoft .NET” also available on Amazon.com.

To analyze your code using the same settings I used in these articles, I encourage you to incorporate my EditorConfig file. It can be found at the following link: https://bit.ly/dotNetDaveEditorConfig. I update this file quarterly, so remember to keep yours up to date as well. I hope you will check out my OSS project Spargine by using this link: https://bit.ly/Spargine.

Please feel free to leave a comment below. I would appreciate hearing your thoughts and feedback.

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