Suggestion for a business logic

We have no idea what "Some" products require a price or where this information is stored in your application. Write code in the controller that looks up the product to figure out if the product requires a price or not. If a price is required but the client did not send the price then add an error message to the ModelState.

ModelStateDictionary.AddModelError Method

ModelState.AddModelError("Price", "A price is required for this product");

thank you, I will check it out and let you know.

Hi @Cenk

Some product codes must be sent with quantity and price. How can I associate price with related products?

This is a design issue.

After user enter/select the product codes, you can load the related price based on the product codes (need another endpoint to get the price based on the product code). Then you can select the price, in this scenario, the product and price are related.

Or if you don't want to use above method, you could use a textbox to display the price, and when submit the form, send the product code with the price and quantity. Then, in the API action method, do something based on the produce code, quantity and price.

No matter using which kind of methods, you have to add a price property in the RequestDto model.

How to make the price required for related product codes in the DTO?

Do you mean you want to add a conditional validation, validate the price based on the product codes? If that is the case, you might need to add Custom validation, refer the following threads:

Validate when not empty

Conditional remote validation in Razor Pages

Best regards,
Dillion

Can I use the model state in the service layer instead of the controller?

ModelState.AddModelError("Price", "A price is required for this product");

Here is the controller:

[Route("purchase")]
        public async Task<IActionResult> PurchaseGame([FromForm] RequestDto game)
        {
            if (!ModelState.IsValid) return BadRequest(ModelState);

           
            var gameConfirmResponse = game.productCode switch
            {
                var x when razerGameList.Contains(x) =>
                    //Call Razer
                    await _services.RazerPurchase(game),
                var y when zulaGameList.Contains(y) =>
                   //Call Zula
                   await _services.ZulaPurchase(game),
                var z when ezpinGameList.Contains(z) =>
                   //Call Ezpin
                   await _services.EzpinPurchase(game),

                _ => //Call Stock
                    await _services.RazerPurchase(game),

            };

And here is the service layer I want to make validation;

private async Task<HttpResponseMessage?> EzpinPurchase (RequestDto requestDto)
        {
            
          
            //ProductCode Conversion
            var productCode = _unitOfWork.ProductCodeRepository.GetByCode(p =>
                p.clientCode == requestDto.productCode);
            if (productCode != null)
            {
                requestDto.productCode = productCode.gameCode;
            }

A better approach would be doing this validation with data annotations or something in the DTO. Is there any chance? Some sort of conditional validation. Forgot to mention, the price property is not mandatory either.

public class RequestDto
    {
        [Required(ErrorMessage = "Please add Product Code to the request.")]
        [MaxLength(15, ErrorMessage = "The product code can not be more than 15 characters")]
        public string productCode { get; set; }

        [Required(ErrorMessage = "Please add Quantity to the request.")]
        [Range(1, 100, ErrorMessage = "The quantity must be added.(quantity = 1)")]
        public int quantity { get; set; }
        [SwaggerSchema(ReadOnly = true)]
        public string? shopNo { get; set; }
        [SwaggerSchema(ReadOnly = true)]
        public string? safeNo { get; set; }
        [SwaggerSchema(ReadOnly = true)]
        public string? cashierNo { get; set; }
        [SwaggerSchema(ReadOnly = true)]
        public string? clientTrxRef { get; set; }
        public string? price { get; set; }

    }