How to create Single Custom Action Filter in asp.net core to validate GET & POST request parameters?

Question

Want to create 'Custom Action Filter' in asp.net core, which basically performs some validation logic on the incoming GET & POST request related input parameters then throw validation exception if validation fails or allow the execution to proceed further on validation success.

Is it possible to create one single 'Custom Action Filter' to validate GET & POST request parameters with out using 'if else'(like sample mentioned below)? As you all know usually parameter comes as part of query string for GET request whereas parameter comes as part of request body for POST request

Considering SRP principle, I don't want to create input parameter validation code as part of controller/action logic code.

I can't use Model validation in my case.

public class MyModel 
{
  public string id{ get; set; }

  public string orderId{ get; set; }
}

    [HttpPost]
    public async Task<IActionResult> Login([FromBody] MyModel model)
    {
    }


    [HttpGet]
    public async Task<IActionResult> GetAsync(string id, string orderId)
    {
    }

   public class Validate : ActionFilterAttribute
   {
    public override async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)

    { 
      if (context.HttpContext.Request.Method == "GET" )
        {
           //consider parameters from query string
           //parameter validation logic
        }

        if (context.HttpContext.Request.Method == "POST" )
        {
           //consider parameters from body
           //parameter validation logic
        }           

     }
   }