Empty string not binding to Nullable Guid

Question

So, I have a model which has a Nullable<Guid> property.

public Guid? SupplierID { get; set; }

The raw body has it coming through as "SupplierID":"". But the application isn't converting it to null, and instead throws a formatting exception.

You can see in the above screenshot that the model is a little more complicated.

This is my controller end point:

[HttpPost]
public async Task<ActionResult> Update([FromBody]TemplateJSONViewModel viewModel)

Things I've tried:

If I remove the [FromBody] attribute, it doesn't bind from the body at all - even though it's a complex type and my understand was FromBody is the default - so perhaps that's a clue?

I've changed the model binding to be a string instead, and it binds fine - coming through as "".

---

What can cause this? I've not had any issues with "" binding to Null before.

Many thanks for any help, and taking the time to read!

Answer 1

The Json value is not a supported Guid format.

As the error message in the picture shows,

The GUID is formatted for a display with separators. For example: "{CD9FE4B6-AE1D-448c-B157-D9EA074726CF}"

You bind "" to SupplierID, this ""is a string format, and Guid format is also string , but the format of "" is not the Guid format, Guid format is like "CD9FE4B6-AE1D-448c-B157-D9EA074726CF". You also can set null to the SupplierID if you don't want give value to SupplierID. But you just cannot set Guid format to "".These are two different strings.