Html table data to json and send it mvc controller to list

The {} in JSON tells the de-serializer that it is going to create an object. Keeping this in mind, the JSON you created would make a single object - with each property containing an array of strings. It seems like you want a list of objects, rather than this.

Are you using this method to de-serialize?

JsonConvert.DeserializeObject<T>(json)

You need to provide a type to de-serialize to. So in this case it would be:

class JobDetails
{
    public string JobCode { get; set; }
    public double Hours { get; set; }
    public double Rate { get; set; }
    public double Expense { get; set; }
}

In order to de-serialize to this type your JSON.NET JsonConvert call would look like:

    [HttpPost]
    public ActionResult Testing(string json)
    {
        var list = JsonConvert.DeserializeObject<List<JobDetails>>(json)
        UPDATE_YOUR_MODEL_HERE(list);

        return WHAT_YOU_WANT_TO_RETURN_HERE;
    }

Your JSON would look like:

[
    {
        "JobCode": "a1",
        "Hours": 37.5,
        "Rate": 10,
        "Expense": 375
    },
    {
        "JobCode": "a2",
        "Hours": 10,
        "Rate": 20,
        "Expense": 200
    },
    {
        "JobCode": "a3",
        "Hours": 37.5,
        "Rate": 20,
        "Expense": 750
    }
]

This will convert the JSON into a List of JobDetails objects.

Alternatively if you want to resolve the JSON to objects as an Action parameter this should do the trick:

    [HttpPost]
    public ActionResult Testing(List<JobDetails> list)
    {
        UPDATE_YOUR_MODEL_HERE(list);

        return WHAT_YOU_WANT_TO_RETURN_HERE;
    }

If you're having trouble getting your table serialized to correct JSON try looking at this jQuery plug-in: https://github.com/lightswitch05/table-to-json