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Asked: 2026-05-12T23:11:45+00:00

I can’t seem to find any solution to this within SO so here goes.

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I can’t seem to find any solution to this within SO so here goes.

I have a call to a WebMethod within the C# of my page like this;

$.ajax({
    type: "POST",
    url: "MyWebPage.aspx/jQueryMyWebMethod",
    data: "{FamilyType:'" + $('.HdnFamilyType').val() + "'}",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function(msg) {
        var obj = eval('(' + msg + ')');
    }
});

In the code behind I create an object, serialise it and return it like this;

LHCRequiredFormViewModel fvm = new LHCRequiredFormViewModel();
DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(LHCRequiredFormViewModel));
MemoryStream ms = new MemoryStream( );
ser.WriteObject(ms, fvm);
return Encoding.Default.GetString(ms.ToArray());

However, in the Javascript when I do the eval I get the error;

Expected ‘]’;

At the point of returning the serialised object from C# the data looks like; 

"{\"<IsApplicantLHCRequired>k__BackingField\":true,\"<IsPartnerLHCRequired>k__BackingField\":false}"    string

I should mention that the project was .Net 2.0 and I was simply returning a serialised object w/out all the JSON guff and it worked fine.

So I then converted to 3.5 and the problem began. It’s then that I used the JsonSerializer but am still getting exactly the same error.

Anyone know what’s going on and how to fix it?

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1 Answer

  1. Editorial Team

    A long time ago I had a problem similar to this. Unfortunately it was so long ago that I can’t remember how I ended up fixing it. I just know that the root cause was going from old version of .NET to 3.5.

    If my memory serves me correctly try these:
    Try using a different de-serializer on the client. Such as Json Parse from http://www.json.org/json_parse.js

    If that still doesn’t work. Try a different serializer on the server. Json.NET is free and provides a lot of control over how you want to serialize your data: http://www.codeplex.com/Json

    Or maybe I just needed to set the MimeType for the request to be text only instead of HTML.

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