从表格分层数据构建json

Question

Let's say I have some data as you see below:

{
    "Menu": {
        "aaa": "aaa",
        "bbb": {
             "ccc": "ccc",
             "ddd": "ddd"
        },
        "eee": "eee"
     }
}

I can save this type of hierarchical data to database in a relational way like that:

http://i.stack.imgur.com/lmuq1.jpg

Sample list:

    List<MenuItem> menuItems = new List<MenuItem>();
    menuItems.Add(new MenuItem() { SiteMenuId = 1, ParentId = null, MenuName = "Menu", Url = null, SiteId = 1 });
    menuItems.Add(new MenuItem() { SiteMenuId = 2, ParentId = 1, MenuName = "aaa", Url = "aaa", SiteId = 1 });
    menuItems.Add(new MenuItem() { SiteMenuId = 3, ParentId = 1, MenuName = "bbb", Url = null, SiteId = 1 });
    menuItems.Add(new MenuItem() { SiteMenuId = 4, ParentId = 3, MenuName = "ccc", Url = "ccc", SiteId = 1 });
    menuItems.Add(new MenuItem() { SiteMenuId = 5, ParentId = 3, MenuName = "ddd", Url = "ddd", SiteId = 1 });
    menuItems.Add(new MenuItem() { SiteMenuId = 6, ParentId = 1, MenuName = "eee", Url = "eee", SiteId = 1 });

So when I get the relational data from db as a List of MenuItem objects, how can I tranlate it back to json?

public partial class MenuItem
{
    public int SiteMenuId { get; set; }
    public int SiteId { get; set; }
    public string MenuName { get; set; }
    public string Url { get; set; }
    public Nullable<int> ParentId { get; set; }
    public int CreatedUser { get; set; }
    public System.DateTime CreatedDate { get; set; }
    public Nullable<int> ModifiedUser { get; set; }
    public Nullable<System.DateTime> ModifiedDate { get; set; }
} 

Do I have to use Dictionary or ExpandoObject or something? I want to have the the exact same format as I have at the begining.

Answer 1

You can create KeyValuePair object for that purpose:

KeyValuePair<string, List<Object>> toExport = new KeyValuePair<int, int>("Menu", new List<Object>());

Then, you can add elements, like this:

toExport.Value.Add(new KeyValuePair<string, string>("aaa", "aaa"));

To add composite things to this, you can do something like that:

KeyValuePair<string, List<Object>> bbb = new KeyValuePair<string, List<Object>>("bbb", new List<Object>());
bbb.Value.Add(new KeyValuePair<string, string>("ccc", "ccc"));
bbb.Value.Add(new KeyValuePair<string, string>("ddd", "ddd"));
toExport.Value.Add(bbb);

When you have built your object, you can use NewtonSoft's JsonConvert.SerializeObject method.

You can also create a helper class to help you.

EDIT: Creation of dynamic data.

public class DynamicKeyValueBuilder {

    private KeyValuePair<string, List<Object>> toExport;

    public DynamicKeyValueBuilder(string mainKey) {
        toExport = new KeyValuePair<string, List<Object>>(mainKey, new List<Object>());
    }

    public string getJSON() {
        return JsonConvert.SerializeObject(this.toExport);
    }

    private KeyValuePair<string, List<Object>> searchParent(List<string> path) {
        KeyValuePair<string, List<Object>> temp = (KeyValuePair<string, List<Object>>)this.toExport;
        int index = 0;
        while (index < path.Count) {
            try {
                temp = (KeyValuePair<string, List<Object>>)temp.First(item => item.Key == path.ElementAt(index)); //throws exception if value is not list or the element was not found
                index++;
            } catch (Exception exception) {
                //handle exceptions
                return null;
            }
        }
        return temp;
    }

    //If value == null, we create a list
    public boolean addElement(List<string> path, string key, string value) {
        KeyValuePair<string, Object> parent = this.searchParent(path);
        //failure
        if (parent == null) {
            return false;
        }
        parent.Value.Add((value == null) ? (new KeyValuePair<string, List<Object>>(key, new List<Object>())) : (new KeyValuePair<string, string>(key, value)));
        return true;
    }

}

Code is untested, if you encounter errors, please, let me know instead of just down-voting, I believe I am putting an effort here to help.

You can instantiate the class like this:

DynamicKeyValueBuilder myBuilder = new DynamicKeyValueBuilder("Menu");

When you intend to add a new <string, string> element, you can do it like this:

myBuilder.Add(new List<string>(new string[] {"Menu"}), "aaa", "aaa");

When you intend to add a new <string, List<Object>> element, you can do it like this:

myBuilder.Add(new List<string>(new string[] {"Menu"}), "bbb", null);

When you intend to add something inside an inner list, you can do it like this:

myBuilder.Add(new List<string>(new string[] {"Menu", "bbb"}), "ccc", "ccc");

Answer 2

using Json.net , we can write a custom converter to generate our desired json from list of MenuItem .

NOTE: I omitted the reader part for the converter to make it concise (as its not really related to the question) but the logic would be similar to the writer part.

class MenuItemJsonConverter : JsonConverter
{

    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof (MenuItemCollection) || objectType==typeof(List<MenuItem>);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        var map=new Dictionary<int,JObject>();
        var collection = (List<MenuItem>) value;
        var root=new JObject();

        var nestedItems=collection.GroupBy(i => i.ParentId).ToLookup(g=>g.Key); //or we can simply check for item.Url==null but I believe this approach is more flexible

        foreach (var item in collection)
        {
            if (item.ParentId == null)
            {
                var firstObj=new JObject();
                root.Add(item.MenuName,firstObj);
                map.Add(item.SiteMenuId,firstObj);
                continue;
            }

            var parent = map[item.ParentId.Value];

            if (!nestedItems.Contains(item.SiteMenuId))
            {
                parent.Add(item.MenuName,item.Url);
                continue;
            }

            var jObj = new JObject();
            parent.Add(item.MenuName, jObj);
            map.Add(item.SiteMenuId, jObj);
        }

        writer.WriteRaw(root.ToString());
    }
}

here is direct usage example:

        var menuItems = new List<MenuItem>();
        menuItems.Add(new MenuItem() { SiteMenuId = 1, ParentId = null, MenuName = "Menu", Url = null, SiteId = 1 });
        menuItems.Add(new MenuItem() { SiteMenuId = 2, ParentId = 1, MenuName = "aaa", Url = "aaa", SiteId = 1 });
        menuItems.Add(new MenuItem() { SiteMenuId = 3, ParentId = 1, MenuName = "bbb", Url = null, SiteId = 1 });
        menuItems.Add(new MenuItem() { SiteMenuId = 4, ParentId = 3, MenuName = "ccc", Url = "ccc", SiteId = 1 });
        menuItems.Add(new MenuItem() { SiteMenuId = 5, ParentId = 3, MenuName = "ddd", Url = "ddd", SiteId = 1 });
        menuItems.Add(new MenuItem() { SiteMenuId = 6, ParentId = 1, MenuName = "eee", Url = "eee", SiteId = 1 });

        var json = JsonConvert.SerializeObject(menuItems,Formatting.Indented,new MenuItemJsonConverter());

or we can derive from List<> and decorate it with [JsonConverter(typeof(MenuItemJsonConverter))] for more convenience:

[JsonConverter(typeof(MenuItemJsonConverter))]
class MenuItemCollection : List<MenuItem>
{      
}

then simply use it like:

        var menuItems = new MenuItemCollection();
        menuItems.Add(new MenuItem() { SiteMenuId = 1, ParentId = null, MenuName = "Menu", Url = null, SiteId = 1 });
        menuItems.Add(new MenuItem() { SiteMenuId = 2, ParentId = 1, MenuName = "aaa", Url = "aaa", SiteId = 1 });
        menuItems.Add(new MenuItem() { SiteMenuId = 3, ParentId = 1, MenuName = "bbb", Url = null, SiteId = 1 });
        menuItems.Add(new MenuItem() { SiteMenuId = 4, ParentId = 3, MenuName = "ccc", Url = "ccc", SiteId = 1 });
        menuItems.Add(new MenuItem() { SiteMenuId = 5, ParentId = 3, MenuName = "ddd", Url = "ddd", SiteId = 1 });
        menuItems.Add(new MenuItem() { SiteMenuId = 6, ParentId = 1, MenuName = "eee", Url = "eee", SiteId = 1 });

        var json = JsonConvert.SerializeObject(menuItems,Formatting.Indented);

Answer 3

If you can use NewtonSoft, use to deserialize your JSON content and see how the resulting object looks like. Then, create a class that matches the resulting structure of the deserialization. Reverse engineering...

Use this method:

var obj = JsonConvert.DeserializeObject("{ "menu": { "aaa": "aaa"......} }");

Let me know your findings.