Confusion over maxJsonLength default value

Question

I\'m hoping to get some clarification on the maxJsonLength property. Here is some background information.

I was having an issue with an AJAX response not being returned

Answer 1

There are two defaults for MaxJsonLength depending on how JavaScriptSerializer is created.

2 097 152

It is 2097152 when serializer is created directly. Relevant code is:

public class JavaScriptSerializer {
    ...
    internal const int DefaultMaxJsonLength = 2097152;        
    ...
    public JavaScriptSerializer(...) {
        ...
        MaxJsonLength = DefaultMaxJsonLength;
    }
}

102 400

It is 102400 when serializer is created by ASP.NET MVC (or older). Relevant code is:

public sealed class ScriptingJsonSerializationSection : ConfigurationSection {
    ...
    private static readonly ConfigurationProperty _propMaxJsonLength =
        new ConfigurationProperty("maxJsonLength",
                                    typeof(int),
                                    102400,
                                    ...);
    ...
    [ConfigurationProperty("maxJsonLength", DefaultValue = 102400)]
    public int MaxJsonLength { ... }
    ...
}

There are several places which assign serializer.MaxJsonLength to this value — all of them are in ASP.NET-related code.

Answer 2

Creating a page on a website with the following in the code behind:

JavaScriptSerializer serializer = new JavaScriptSerializer();

Response.Write("Max Length: " + serializer.MaxJsonLength);

Led to an output of:

Max Length: 2097152

So I would go with the value defined in the docs rather than the How to.

Note however that this is Characters, and not bytes explicitly:

The default is 2097152 characters, which is equivalent to 4 MB of Unicode string data

Answer 3

I ran into similar issues returning JSON from a web service. I set the maxJsonLength in web.config to a value large enough to handle the data I was sending back.