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Describe the bugUse HttpClient to post request to another site will result in exception To Reproduce
Exceptions (if any)Further technical details
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Replies: 8 comments 10 replies
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Is there a question? Blazor wasm has the same restrictions running JavaScript in the browser (it all runs in the same sandbox) |
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Are you saying that this issue is by design? I can see the same snippet works fine in Blazor server app, console app, desktop app. Can you elaborate more on why Blazor wasm doesn't work? |
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You can enable cross-origin requests provided that the server supports CORS using the following extension method |
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This looks great! So where do I place this snippet? |
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Yup. Blazor WebAssembly runs in your browser where particular security features are forced. One of them you met. If you run Blazor Server Side then your code runs (communicates other sites) at your server - which is not your browser - and send the DOM changes to your browser via SignalR. That is the difference. It is a SO article explains some details, there are might be better articles about it. |
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Thanks, very useful and clear for me. So in my issue, the only way it can work is the other site (https://login.microsoftonline.com/xxxxxxxxxxx/oauth2/token) must return response with header including Access-Control-Allow-Origin = "*", right? |
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You can use CORS in Blazor Webassembly as well as configuring other |
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Where i can add this line into my code? |
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You can use CORS in Blazor Webassembly as well as configuring other fetch options ?? How to do it. |
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Hi @javiercn ,below is my code where i am setting the default browser as CORS but still getting the same error. |
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Is the server returning the appropriate CORS headers in response? |
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Thank You @javiercn I did this via proxy. I created a Proxy API and routed my endpoint via this proxy API |
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can you please share some content how to create Proxy API. |
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Need this as well pls |
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I'm trying to get data from an IoT device and the only thing that doesn't throw is The request payload is something like: And the device replies with: However, there's no body. The device replies with 200 and if I issue the same request in Fiddler, I get the response body with the same 125 bytes length. If I set Fiddler as a proxy, I can see in Fiddler the content. |
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@paulomorgado If you are querying a different origin and they don't send back CORS requests (seems the device isn't) there's nothing you can do. Also that thing is replying with HTTP/1.0 (not even 1/1) so it's incredibly old and likely to run into all sort of weird compat issues. |
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@javiercn, what CORS headers they need to send back? |
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The CORS docs on MDN do a much better job than me at explaining this in depth https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS |
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Hi @javiercn ,below is my code where i am setting the default browser as CORS but still getting the same error.
Could you please give us your working code repo.
builder.Services.AddTransient(sp => new HttpClient(new DefaultBrowserOptionsMessageHandler(new WebAssemblyHttpHandler())
{
//DefaultBrowserRequestCache = BrowserRequestCache.NoStore,
//DefaultBrowserRequestCredentials = BrowserRequestCredentials.Omit,
DefaultBrowserRequestMode = BrowserRequestMode.Cors,
})
{
BaseAddress = new Uri(builder.HostEnvironment.BaseAddress),
});