Question 85710 in ASP.NET Question posted in
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In ASP.NET WebApi, my entire POST model becomes null if a GUID property is invalid

I have this model

public class FooModel
{
  public Guid ReferenceId { get; set; } // <-- this is the important part
  public string SomeValue { get; set; }
}

And I have this controller endpoint

[HttpPost]
[ProducesResponseType(200)]
public async Task<IActionResult> SaveFoo([FromBody] FooModel model, CancellationToken ct)
{
  await _fooManager.SaveFoo(model, ct);
  return Ok();
}

My problem

If the client POSTS a json that looks like this with an invalid GUID for referenceId, The entire model object received is null.

{
  "referenceId": "some-invalid-guid!",
  "someValue": "some valid value"
}

My desired outcome

I want the object that the endpoint receives to not be null, and contain the other values that were assigned. The referenceId GUID would be either null or empty.

What I tried

I tried making the Guid nullable. Example: public Guid? ReferenceId { get; set; }

However this did not work. I imagine there is some de-serialization setting I need to change somewhere in my WebApi project, but I don’t know where.

Tags:

2

Answers


  1. 0

    I recommend declaring ReferenceId as a string instead of Guid. Then use
    Guid.TryParse to validate ReferenceId after the post.

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  2. 0

    the only way to fix it is to use JsonElement as input parameter (or JObject if you use Newtonsoft.Json)

    [HttpPost]
 public async Task<IActionResult> SaveFoo([FromBody] JsonElement element, CancellationToken ct)
{
    string referenceId = element.GetProperty("ReferenceId").GetString();

    if(Guid.TryParse(referenceId, out var referenceGuid))
   {
     FooModel model = element.Deserialize<FooModel>();
      //... your code
   }
     
}

    Newtonsoft

    [HttpPost]
 public async Task<IActionResult> SaveFoo([FromBody] JsonObject obj, CancellationToken ct)
{
   string referenceId = (string) obj["ReferenceId"];

    if(Guid.TryParse(referenceId, out var referenceGuid))
   {
     FooModel model = jObj.ToObject<FooModel>();
      //... your code
   }
     
}
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