Postman and ASP.NET MVC POST returns null

postman-mvc-post-returns-null.md

If you are using Postman or manually calling your ASP.NET MVC REST api, and getting a null coming through this could be for various reasons:

[Route("Post")]
[HttpPost)
public string Post([FromBody] MyModel model)
{
   // do something with model
}

public class MyModel
{
    public Guid? Id { get;set; }
}

// Posted JSON:
{
    "Id" : ""
}

• [FromBody] is required for HttpPost
• This also enables Swagger (NSwag) calls to be tried out correctly, however it sees everything as a string.
• NSwag needs [Route] attributes to recognise your method
• NSwag errors can be found out by looking at its JSON file.
• Postman needs Content-Type: application/json and a Raw body
• Your model properties need to be nullable if they are optional
• Your model needs a parameterless constructor.