C#•13mo ago

✅ How to parse this weird API ?

I have a very akward thing to do and I d'ont know if there is a clean way to do it. In a REST API, there is two string fields attributeName and attributeValue (for example { "attributeName" : "isAllowed" , " attributeValue" : "true"} and { "attributeName" : "productType" , " attributeValue" : "A50"} , in the API this is modelled by the following class N.B: the "attribute" here have nothing to do with any .NET vocabulary, it's just a name, think of it like "foo" or "bar"

public record ApiCommand
{
    public string? AttributeName {get; init;}
    public string? AttributeValue {get; init;} 
}

public record ApiCommand
{
    public string? AttributeName {get; init;}
    public string? AttributeValue {get; init;} 
}

In my Domain I have a class with all possible properties

public record Porduct 
{
    public bool? IsAllowed {get; init;}
    public ProductType? ProductType {get; init;} // ProductType is an enum
    // There are other properties as well
}

public record Porduct 
{
    public bool? IsAllowed {get; init;}
    public ProductType? ProductType {get; init;} // ProductType is an enum
    // There are other properties as well
}

what I need to do is, depending on the AttributeName and AttributeValue given in the API, I want to create an instance of Product which has all everything equal to null except for the property for which we were given the name and value in AttributeName and AttributeValue. (there is always a single one) For exemple { "attributeName" : "isAllowed" , " attributeValue" : "true"} would result in a product Instance with product.IsAllowed = true and product.ProductType = null (and other fields will be null as well) Another example, { "attributeName" : "productType" , " attributeValue" : "A50"} would result in product Instance with product.IsAllowed = null and product.ProductType = A50 (and other fields will be null as well)

64 Replies

LazyGuard•13mo ago

. my attempt is something that i find very ugly:, it's something like this:

produt = new Product() // an instance where everything is null;
if (model.AttributeName.toLower() == "isallowed") 
{
  if (model.AttributeValue == "true")
  {
    return new product with {IsAllowed = true}
  }
  else if (model.AttributeValue == "false")
  {
    return new product with {IsAllowed = false}
  }
  //else return some error 
}
// other ifs for other properties like productType

produt = new Product() // an instance where everything is null;
if (model.AttributeName.toLower() == "isallowed") 
{
  if (model.AttributeValue == "true")
  {
    return new product with {IsAllowed = true}
  }
  else if (model.AttributeValue == "false")
  {
    return new product with {IsAllowed = false}
  }
  //else return some error 
}
// other ifs for other properties like productType

for 10 properties to handle, it will be a huge mess :/ Any help ?

sibber•13mo ago

make a method in ApiCommand that maps to Product btw, ApiCommand is what we call a data transfer object (DTO), and the conventional way to name it is ProductDTO oh wait i think i misunderstood you

daysleeper•13mo ago

https://learn.microsoft.com/en-us/dotnet/csharp/advanced-topics/reflection-and-attributes/ try reflection maybe can help

Attributes and reflection

Use attributes to associate metadata or declarative information with code in C#. An attribute can be queried at run time by using reflection. Reflection provides objects that describe assemblies, modules, and types in C#. If your code includes attributes, reflection enables you to access them.

sibber•13mo ago

ApiCommand returns the value of a single property for a product? thats not what they mean by attribute

LazyGuard•13mo ago

yeah, attribute belongs to a domain vocabulary, that have nothing to do with the meaning of an attribute in C# 😆 I will edit my Original post to be more clear

sibber•13mo ago

LazyGuard•13mo ago

yup ApiCommand always have the name and value of a signle property of product

sibber•13mo ago

what a shitty api so that means you need to query the endpoint for each property of Product?

LazyGuard•13mo ago

no it's more complicated I tried to create a simple example to be able to communicate what I need to do unfortunately I don't have the ability to change the ApiCpmmand you can think of it as a product will always have everything null except for one property

sibber•13mo ago

i dont see how thats different from what i said

daysleeper•13mo ago

i understand that. reflection can help you access metadata like

  var type = typeof(Model);
  var properties = type.GetProperties();
  foreach(var property in properties)
  {
    var propertyName = property.Name; (that's where you can compare them or something)
    // do something
  }

  var type = typeof(Model);
  var properties = type.GetProperties();
  foreach(var property in properties)
  {
    var propertyName = property.Name; (that's where you can compare them or something)
    // do something
  }

sibber•13mo ago

im aware at that point i didnt understand op's question but yeah that could be useful, although i still dont fully understand what op is trying to do lol

LazyGuard•13mo ago

The endpoind is a POST. When the body has { "attributeName" : "isAllowed" , " attributeValue" : "true"} it would result in creating a Product Instance with product.IsAllowed = true and product.ProductType = null (and all other properties will be null as well). That instance will then be saved in the Db

sibber•13mo ago

ah and you just need to set this one property in your model

LazyGuard•13mo ago

yup everytime it's just one property

sibber•13mo ago

do you make the post req in the same app? obviously, that was a stupid question lol i meant to ask, how do you make the post requeist how do you provide attributeName

LazyGuard•13mo ago

it's exposed by my app to the users who have some client coded

sibber•13mo ago

wait youre writing the api? so youre recieving the post request? the ApiCommand instance?

LazyGuard•13mo ago

yup

sibber•13mo ago

ah alright, you have 2 options: 1. use reflection 2. write a source gen id go with 1 in your case

LazyGuard•13mo ago

😢 I feel that it's very shitty

sibber•13mo ago

its not its made for things like this thats what a lot of serializers use actually theres a third option re design your api

LazyGuard•13mo ago

I can't :(, it's designed by some """"""tech lead""""""" :/

sibber•13mo ago

oof welp reflection it is

LazyGuard•13mo ago

If it was me I would go with something that mirror Product in the Api :/

sibber•13mo ago

yes thats what sane people would do unless im missing some context

LazyGuard•13mo ago

if I try to do this using reflection, can't see how this is helpful :/

 var type = typeof(Model);
  var properties = type.GetProperties();
  foreach(var property in properties)
  {
    var propertyName = property.Name; //(that's where you can compare them or something)
    // do something
  }

 var type = typeof(Model);
  var properties = type.GetProperties();
  foreach(var property in properties)
  {
    var propertyName = property.Name; //(that's where you can compare them or something)
    // do something
  }

(it's the message posted by @daysleeper00 ) ah, Model here is Product ? I thought it was ApiCommand

daysleeper•13mo ago

you can first validate fields by searching for them and then invoke a method like UpdateFields() where invoke property.SetValue(). i think its pretty easy if you research a bit about reflection

sibber•13mo ago

well what you want to do is get the property named ApiCommand.attributeName

sibber•13mo ago

https://learn.microsoft.com/en-us/dotnet/api/system.type.getproperty?view=net-7.0

Type.GetProperty Method (System)

Gets a specific property of the current Type.

LazyGuard•13mo ago

but i still need to compare apiCommand.AttributeName with property.Name for every preperty in properties. = Product.GetProperties() right ?

sibber•13mo ago

no read the doc i sent GetProperty returns null if the property doesnt exist actually maybe that would be faster if you cache the property infos

LazyGuard•13mo ago

still can't see how to use it 😆 , something like product.GetProperty("isAllowed") won't help me the input is ApiCommand. and not the Product

daysleeper•13mo ago

read about reflection first and when you understand how it works you will get this done trust me

LazyGuard•13mo ago

okay !

sibber•13mo ago

did you read this?

Pobiega•13mo ago

How many properties are there? Are they likely to change in the future?

sibber•13mo ago

this is in a post endpoint theyre recieving an ApiCommand instance, and they want to create a Product and set the property that is in ApiCommand thats the TLDR

Pobiega•13mo ago

I'm aware.

sibber•13mo ago

Pobiega•13mo ago

I'm asking for how many properties there are on Product

sibber•13mo ago

Pobiega•13mo ago

if its a low number, and not likely to change, a reflection based approach seems overkill

sibber•13mo ago

oh yeah if its low enough you could switch on ApiCommand.balblaName idk why i didnt think of that

Pobiega•13mo ago

actually, a source generator would be a very cool solution.. and also very likely massively overkill in terms of effort 😄 exactly

LazyGuard•13mo ago

there is ~15 properties

Pobiega•13mo ago

alright. thats... doable on a switch, but might not feel very clean.

LazyGuard•13mo ago

I did but not sure I fully understand it :/. It lacks some examples

sibber•13mo ago

look at the last overload

sibber•13mo ago

this one https://learn.microsoft.com/en-us/dotnet/api/system.type.getproperty?view=net-7.0#system-type-getproperty(system-string)

Type.GetProperty Method (System)

Gets a specific property of the current Type.

LazyGuard•13mo ago

i guess I need to do something like

var property = Product.GetProperty(apiCommand.AttributeName)
// then something like product.property = apiCommand.AttributeValue, not sure about the syntax, I guess there will be some method to do something like this

var property = Product.GetProperty(apiCommand.AttributeName)
// then something like product.property = apiCommand.AttributeValue, not sure about the syntax, I guess there will be some method to do something like this

Pobiega•13mo ago

the second part will have nasty syntax.. something like property.SetValue(product, value); where value is a correctly typed variable holding the parsed content from AttributeValue string, just shove it in. int/bool etc? gotta parse

sibber•13mo ago

typeof(Product).GetProperty although caching the property infos and querying them might be a faster approach, if you care about performance you should benchmark it first tho

LazyGuard•13mo ago

yeah that feels like a very strange syntax yup, I also need to parse strings to properly tyed stuff what do you mean by caching it ?

sibber•13mo ago

storing it somewhere and accessing it not using reflection to get all the properties every time

LazyGuard•13mo ago

Okay, I will give reflection a try, then benchmark it and then maybe cache it in some config file (app.settings for instance)

sibber•13mo ago

dont cache it in a config file that wouldnt work anyway cache it in the class youre doing that in

Pobiega•13mo ago

you'd set up a dictionary or similar, between your string (property name) and the propertyinfo and calculate that once, at startup because reflection is expensive (time-wasting) so doing it once and then storing the results is good practice

sibber•13mo ago

oh right thats a better idea

LazyGuard•13mo ago

what do you mean by "propertyInfo" ?

sibber•13mo ago

look at what this returns

Pobiega•13mo ago

Thats the type you get from typeof(T).GetProperty

LazyGuard•13mo ago

Oh yeah I see, it's still using relfection by only once using some static field to store the result thanks folks

Accord•13mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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✅ How to parse this weird API ?