.NET WebApi Parameter 绑定可选参数

Question

I have a REST API built in .NET WebApi. I have created a custom parameter binding attribute for extracting a value from HTTP headers. There are scenarios where the header may or may not be present on the request, so I would like to be able to do something like the following to treat the header as an optional parameter.

public IHttpActionResult Register([FromBody] RegistrationRequest request, [FromHeaderAuthorization] string authorization = null)
{

This works fine when I call the endpoint with the authorization header included. When calling the endpoint without the header however I get the following error message:

The request is invalid.', MessageDetail='The parameters dictionary does not contain an entry for parameter 'authorization' of type 'System.String'

I have been searching to try and determine if it is possible to treat a parameter as optional in this way and have found some mixed results. It appears that in C# 8.0 I could achieve this using a nullable reference type, but Visual Studio indicates that 8.0 is currently in preview and thus not really an option for me. That said, I haven't really been able to find anything else that indicates whether this type of thing is possible or not.

My question is, is it possible to treat this header parameter as optional or do I need to go about this differently?

Answer 1

I ended up abandoning the header parameter and going in a slightly different direction.

I had already created a class to extend HttpRequestMessage to do things like get the IP of the client calling the endpoint, I ended up adding a method to handle checking for the existence of the header and retrieving the necessary identity information as needed.

public static class HttpRequestMessageExtensions
{
    private const string HttpContext = "MS_HttpContext";
    private const string RemoteEndpointMessage = "System.ServiceModel.Channels.RemoteEndpointMessageProperty";

    /* Method body excluded as irrelevant */
    public static string GetClientIpAddress(this HttpRequestMessage request) { ... }

    /** Added this method for handling the authorization header. **/
    public static Dictionary<string, string> HandleAuthorizationHeader(this HttpRequestMessage request)
    {
        Tenant tenant = new Tenant();
        IEnumerable<string> values;
        request.Headers.TryGetValues("Authorization", out values);
        string tenantConfig = ConfigurationUtility.GetConfigurationValue("tenantConfig");

        if (null != values)
        {
            // perform actions on authorization header.
        }
        else if(!string.IsNullOrEmpty(tenantConfig))
        {
            // retrieve the tenant info based on configuration.
        }
        else
        {
            throw new ArgumentException("Invalid request");
        }

        return tenant;
    }
}

Answer 2

We had the similar situation ( ASP .NET Core 6 ) where Header Parameter always considered as mandatory by the framework even though we assigned a default value ( range variable).

public async Task<IActionResult> GetMessages(
            [EmailAddress(ErrorMessage = "Invalid Mailbox Address")][FromRoute][Required] string mailbox,
            [FromRoute][Required] string folderId,
            [FromQuery] GetMessageBodyParameter getMessageBodyParameter,
            [FromHeader] string range = "0-9")

And we flagged the variable as nullable ( string? range ) and it is working fine now.

public async Task<IActionResult> GetMessages(
            [EmailAddress(ErrorMessage = "Invalid Mailbox Address")][FromRoute][Required] string mailbox,
            [FromRoute][Required] string folderId,
            [FromQuery] GetMessageBodyParameter getMessageBodyParameter,
            [FromHeader] string? range = "0-9")