.NET MVC Databind JSON Object with Array of Objects

Question

I have a need to databind a JSON object, where the receiving model has a list of another model. Example:

public class User
{
    public string FirstName;
    public string LastName;
    public List<Friend> Friends;
}

Friend class:

public class Friend
{
    public string NickName;
    public string FirstMetLocation;
}

I need to build a JSON object that databinds to the User model when I call an action.

The way I'm building my JSON object is like so:

var friends = [];
// iterate over something and add friend object to array
friends.push({
    NickName: 'Bongos',
    FirstMetLocation: 'That place'
});

var user = {
    FirstName: 'Joe',
    LastName: 'Somebody',
    Friends: friends
};

That ends up producing JSON like so:

{"FirstName":"Joe","LastName":"Somebody","Friends":[{"NickName":"Bongos","FirstMetLocation":"That place"}]}

I'm then passing it on to my action through an AJAX POST:

$.ajax({
    type: 'POST',
    url: url,
    dataType: 'json',
    data: user,
    success: function (event) {
        // do something
    },
    error: function (xhr, status, error) {
        alert("You didn't do it right.");
    }
});

When it gets to action the User object picks up the FirstName and LastName properties, but the List<Friend> is null. When I strip it down to just passing in a List<Friend> It works fine. That JSON looks like so:

{"Friends":[{"NickName":"Bongos","FirstMetLocation":"That place"}]}

Am I missing something?

Shyju · Accepted Answer · 2017-06-20 20:47:15Z

1

Since it is a complex object, specify the content type as application/json and send the data as stringified json string.

$.ajax({
    type: 'POST',
    url: url,
    contentType: 'application/json',
    data: JSON.stringify(user),
    success: function (event) {
        // do something
    },
    error: function (xhr, status, error) {
        alert("You didn't do it right.");
    }
});

Now model binder will be able to map the data sent from the ajax call to the corresponding properties

Also assuming your properties are settable.

public class User
{
    public string FirstName { set; get; }
    public string LastName { set; get; }
    public List<Friend> Friends { set; get; }
}

public class Friend
{
    public string NickName { set; get; }
    public string FirstMetLocation { set; get; }
}

edited Jun 20, 2017 at 20:47

answered Jun 20, 2017 at 20:38

Shyju

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1 Comment

Davey Jones Over a year ago

Thanks for the response! I'll give this a go as soon as I can. My properties are settable. Is there a reason why the model binder can't handle complex objects the way I've done it?

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