cefsharp/CefSharp · error · ArgumentNullException

request

Error message

request

What it means

ArgumentNullException(nameof(request)) from the UrlRequest(IRequest request, IUrlRequestClient urlRequestClient, IRequestContext requestContext) constructor in the CefSharp wrapper. Creating an out-of-context URL request requires a non-null IRequest; null fails immediately. The request is unwrapped (request.UnWrap()) before being handed to the core constructor, so it must be a valid wrapper instance.

Source

Thrown at CefSharp.Core/UrlRequest.cs:45

        {

        }

        /// <summary>
        /// Create a new URL request that is not associated with a specific browser or frame.
        /// Use <see cref="IFrame.CreateUrlRequest(IRequest, IUrlRequestClient)"/> instead if you want the
        /// request to have this association, in which case it may be handled differently.
        /// For requests originating from the browser process: It may be intercepted by the client via <see cref="IResourceRequestHandler"/>  or <see cref="ISchemeHandlerFactory"/>.
        /// POST data may only contain only a single element of type PDE_TYPE_FILE or PDE_TYPE_BYTES.
        /// </summary>
        /// <param name="request">request</param>
        /// <param name="urlRequestClient">url request client</param>
        /// <param name="requestContext">request context associated with this requets.</param>
        public UrlRequest(IRequest request, IUrlRequestClient urlRequestClient, IRequestContext requestContext)
        {
            if (request == null)
            {
                throw new ArgumentNullException(nameof(request));
            }

            if (urlRequestClient == null)
            {
                throw new ArgumentNullException(nameof(urlRequestClient));
            }

            urlRequest = new CefSharp.Core.UrlRequest(request.UnWrap(), urlRequestClient, requestContext?.UnWrap());
        }

        /// <inheritdoc/>
        public bool ResponseWasCached
        {
            get { return urlRequest.ResponseWasCached; }
        }

        /// <inheritdoc/>
        public IResponse Response

View on GitHub (pinned to 16bc6e0711)

Solutions

1. Construct the IRequest first (e.g. via frame.CreateRequest() or Cef.UiThreadRunFactory) and pass the non-null reference.
2. Where possible prefer IFrame.CreateUrlRequest(IRequest, IUrlRequestClient) which associates the request with a frame and avoids manual construction.
3. Guard the call site: skip UrlRequest creation if request is null and log the upstream source.
4. Enable nullable reference types and annotate so the compiler flags the null.

Example fix

// before
var req = new UrlRequest(maybeNullRequest, client, ctx); // ArgumentNullException

// after
if (maybeNullRequest == null)
    throw new InvalidOperationException("IRequest not yet materialised for this UrlRequest.");
var req = new UrlRequest(maybeNullRequest, client, ctx);

if (request == null) throw new InvalidOperationException("IRequest not materialised.");
var req = new UrlRequest(request, client, ctx);

public static bool IsUsableRequest(IRequest r) => r != null;

try { return new UrlRequest(request, client, ctx); }
catch (ArgumentNullException ex) when (ex.ParamName == "request")
{ /* construct the request first or skip */ throw; }

When it happens

Trigger: Calling new UrlRequest(null, client, ctx); passing an IRequest obtained from a handler before it is materialised; reusing a request object after it was disposed so it surfaces as null via a helper.

Common situations: Building a custom UrlRequest from a resource request handler and forgetting to construct the IRequest; refactor where the request is now lazily created; code that assumes a callback always supplies a non-null IRequest.

Related errors

• otherRequestContext
• requestContextHandler
• settings
• other
• {prop.Name} is required

AI-assisted analysis of cefsharp/CefSharp@16bc6e0711 (2026-08-13). Data as JSON: /api/errors/569151089ed21ac4. Report an issue: GitHub.