//Prepare the data object
var data = {"name": window.navigator.appName, "version": window.navigator.appVersion};

//Use JSON.stringify to serialize the data object into a string and then pass this string
//to .NET code through eoapi.extInvoke
eoapi.extInvoke("demoAbout", [JSON.stringify(data)]);

//You can use any JSON library. The code below uses Microsoft's JSON
//library. In order to use Microsoft's JSON library, you need to:
//1. Use .NET Framework 4.5 or above;
//2. Reference nuget package System.JSON;
using System.JSON;

//Attach the event handler
webView1.JSExtInvoke += new JSExtInvokeHandler(WebView_JSExtInvoke);

//Event handler code
void WebView_JSExtInvoke(object sender, JSExtInvokeArgs e)
{
    switch (e.FunctionName)
    {
        case "demoAbout":
            //Deserialize the JSON string back to JsonValue object
            JsonValue data = JsonObject.Parse(e.Arguments[0] as string);
            
            //Access each property
            string name = (string)data["name"];
            string version = (string)data["version"];
            break;
    }
}

'You can use any JSON library. The code below uses Microsoft's JSON
'library. In order to use Microsoft's JSON library, you need to:
'1. Use .NET Framework 4.5 or above;
'2. Reference nuget package System.JSON;
Imports System.JSON

'Attach the event handler
AddHandler webView1.JSExtInvoke, New JSExtInvokeHandler(AddressOf WebView_JSExtInvoke)

'Event handler code
Private Sub WebView_JSExtInvoke(sender As Object, e As JSExtInvokeArgs)
    Select Case e.FunctionName
        Case "demoAbout"
            'Deserialize the JSON string back to JsonValue object
            Dim data As JsonValue = JsonObject.Parse(TryCast(e.Arguments(0), String))
            
            'Access each property
            Dim name As String = CStr(data("name"))
            Dim version As String = CStr(data("version"))            
        Exit Select
    End Select
End Sub

//You can use any JSON serializer. The following code uses Microsoft's
//JSON serializer implemented in System.Runtime.Serialization assembly. 
//So you must reference this assembly in order to use the following code. 
//The sample code is based on the following MSDN documentation:
//https://docs.microsoft.com/en-us/dotnet/framework/wcf/feature-details/how-to-serialize-and-deserialize-json-data
using System.Runtime.Serialization;
using System.Runtime.Serialization.Json;

//Data type to be serialized
[DataContract]  
class Person  
{  
    [DataMember]  
    internal string name;  

    [DataMember]  
    internal int age;  
}  

//Create an instance of the data object
Person p = new Person();  
p.name = "John";  
p.age = 42;  

//Serialize to JSON string
MemoryStream ms = new MemoryStream();  
DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(Person));  
ser.WriteObject(ms, p);  
ms.Position = 0;  
StreamReader sr = new StreamReader(ms);  
string json = sr.ReadToEnd();

//Pass the JSON string to the JavaScript function showPersonInfo
webView1.InvokeFunction("showPersonInfo", json);

'You can use any JSON serializer. The following code uses Microsoft's
'JSON serializer implemented in System.Runtime.Serialization assembly.
'So you must reference this assembly in order to use the following code.
'The sample code is based on the following MSDN documentation:
'https://docs.microsoft.com/en-us/dotnet/framework/wcf/feature-details/how-to-serialize-and-deserialize-json-data

'Data type to be serialized
<DataContract>
Class Person
    <DataMember>
    Friend name As String
    <DataMember>
    Friend age As Integer
End Class

'Create an instance of the data object
Dim p As Person = New Person()
p.name = "John"
p.age = 42

'Serialize to JSON string
Dim ms As MemoryStream = New MemoryStream()
Dim ser As DataContractJsonSerializer = New DataContractJsonSerializer(GetType(Person))
ser.WriteObject(ms, p)
ms.Position = 0
Dim sr As StreamReader = New StreamReader(ms)
Dim json As String = sr.ReadToEnd()

'Pass the JSON string to the JavaScript function showPersonInfo
webView1.InvokeFunction("showPersonInfo", json)

function showPersonInfo(json)
{
    //Deserialize the object
    var person = JSON.parse(json);
    
    //Display object properties
    alert("Person name: " + person.name + ", age: " + person.age);
}