如何将jArray转换为jobject

Question

I'm using Newtonsoft.Json lib with C# and encountered a problem. I have a jArray as below:

[{"category": "computer","subcat": "desktop"},
 {"category": "category","subcat": "laptop"},
 {"category": "television","subcat": "LCD"}]

and I want it to be transformed as a jObject as below:

{"computer": ["desktop","laptop"],
 "television": ["LCD"]}

Here want I need is a general method that can handle this type of transformation. Which means this method could also do the trick even if the jArray has a 3rd level property. eg

from

[{"typeA":"a","typeB":"a1","typeC":"a11"},{"typeA":"a","typeB":"a1","typeC":"a12"},
 {"typeA":"a","typeB":"a2","typeC":"a21"}]

to

{"a":{"a1":["a11","a12"],"a2":["a21"]}}

Thanks a lot!

Answer 1

EXTREMELY quick and dirty - with vast room for improvement, but this will get it done:

Use like this:

var input = @"[{""type"":""a"",""typeB"":""a1"",""typeC"":""a11""},
               {""type"":""a"",""typeB"":""a1"",""typeC"":""a12""},
               {""type"":""a"",""typeB"":""a2"",""typeC"":""a21""}]";

var b = JsonConvert.DeserializeObject<List<tmp>>(input);
var result = doIt(b, "type", "typeB", "typeC"); 

With this implementation:

private string doIt(IEnumerable<tmp> objs, params string[] g)
{
    var t = CollapseOrGroup(objs,g);

    return JsonConvert.SerializeObject(t);
}

private dynamic CollapseOrGroup(IEnumerable<tmp> objs, IEnumerable<string> props) 
{
    var firstProp = props.FirstOrDefault();
    if (firstProp == default(string))
        return objs;

    var p = Expression.Parameter(typeof(tmp));
    var m = Expression.Property(p, firstProp);
    var l = Expression.Lambda(m, p).Compile() as dynamic;

    if (props.Count() == 1)
    {
        return Enumerable.Select(objs, l);

    } else {    
        IEnumerable<IGrouping<dynamic, tmp>> g = Enumerable.GroupBy(objs, l);   
        return g.ToDictionary (o => o.Key, o => CollapseOrGroup(o, props.Skip(1)));
    }
}

Prints:

{"a":{"a1":["a11","a12"],"a2":["a21"]}}

Search for Newtonsoft in NuGet and download JSON.Net for this to work

Answer 2

I have encountered the same problem using java. Currently, the solution from my side is to traversal the initial ArrayJSON, then figure out the wanted format.

You can define Type1 as a model, List as the member variable, same operation with Type2 using Type3, this will help make your code easy to be organised.