AV0006: Invalid API version month

Cause

An API version expressed an invalid month.

Rule Description

When an API version is expressed as a date, the specified month must be valid.

Consider the following code:

[ApiController]
[ApiVersion(2026, 13, 1)]
[Route("[controller]")]
public class ExampleController : ControllerBase
{
    [HttpGet]
    public IActionResult Get() => Ok();
}

The month 13 is not a valid API version. The month must be between 1 and 12. This would not detected until runtime.

How to Fix Violations

Update the API version to be well-formed.

[ApiController]
[ApiVersion(2026, 1, 1)]
[Route("[controller]")]
public class ExampleController : ControllerBase
{
    [HttpGet]
    public IActionResult Get() => Ok();
}

When to Suppress Warnings

It is never safe to suppress this rule because a runtime exception will be thrown when the attribute is initialized.