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Editorial Team
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Asked: 2026-06-10T20:38:42+00:00

I am using System.Web.Helpers.Json to deserialize some JSON into dynamic in NET 4. The

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I am using System.Web.Helpers.Json to deserialize some JSON into dynamic in NET 4. The following line fails with this error: TypeInitializationException: Attempt by method 'System.Web.Helpers.Json..cctor()' to access method 'System.Web.Helpers.Json.CreateSerializer()' failed.

var json = Json.Decode(response);

The response is lengthy but valid JSON. What could be the matter here? I have tried LINQPad with a short handcrafted JSON and it worked. Is this a configuration issue of some sort?

[EDIT]

Here is the actual sample JSON. It appears the content is pretty much irrelevant. When this is run in a brand new Console application or LINQPad, it works as expected. But if you try to run the same code from a brand new Windows Forms application, it barfs with the above error.

var json = Json.Decode("{\"r\":{\"0\":{\"id\":\"2\"},\"1\":{\"id\":\"33\"}}}");

[EDIT2]

Actually, it turns out this has nothing to do with project types. The exception is thrown if the project is being debugged. If it is simply run, the exception does not occur. Strange, eh?

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1 Answer

  1. Editorial Team

    I forgot about this question and I found my answer in the meantime. I think it was somewhere on Microsoft’s Connect site but I am not sure. So let’s share it now.

    Basically, in order to workaround this problem you need to make sure “Enable the Visual Studio hosting process” is unchecked in your project’s settings under Debug. I am not sure why it’s happening but this is definitely a way to “fix” it. I stopped searching for answers once I found out about this. It was good enough for me.

    Settings / Debug

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