如何在asp net core 5 controller（用于POST方法）中阻止无效的json请求参数

Question

I'm creating an api in asp net core 5 and cannot figure this one out.

When sending this (via a POST call) to the Api it works as expected (200 is returned):

{
    "existingParameterName1": "value1",
    "existingParameterName2": "value2"
}

When sending this I want to block it and return 400 - Bad request

{
    "existingParameterName1": "value1",
    "existingParameterName2": "value2",
    "nonExistingParameterName": "value3"
}

The post handler method in the controller looks like this:

public class MyRequestType
{
    public string ExistingParameterName1 { get; set; }
    public string ExistingParameterName2 { get; set; }

}

[HttpPost]
public async Task<MyResponseType> Post([FromBody] MyRequestType request)
{
    // when getting here the request has been converted to MyRequestType with 
    // only existingParameterName1 and existingParameterName2 (no nonExistingParameterName)
    // How do I detect if there is any non valid parameters in the request?
    
    // the handling code here...
}

I have tried to do an actionfilter for this and also tried to change MyRequestType to object. Both ways could work but feels wrong. Gut feeling says there is a better way to do this. What is the proper way to do this?

Answer 1

Normally, API should ignore the extra input parameters and process with the passed and required one.

but as you are looking something to implement and want to return the "Bad Request" in case of extra passed parameters.

Not sure about the Asp.Net Core, but works with Asp.Net WebApi you can do this in ModelBinder, just impelement IModelBinder and add your logic there.

IModelBinder is responsible to transform and pass your input json to Action method parameters.