复杂的Json类型查询

Question

I get the JSON from another external vendor and I have simplyfied the same here.

Problem : I am searching for instrumentIdentifier in Holding in the json, have to extract it , it can appear at level 2 or level 3 or level 4 in the assetcategory.

I am not sure how to search it properly using linq or normal C# methods, I don't have latest newtonsoft to query based on JsonPath. Stuck badly using Linq or even normal method,

.net version is 4.0 , newtonsoft 4.5

Answer 1

Use recursion:

public holdings FindHoldings(portfolio portfolio, string instrumentId) 
{
    return FindHoldingsRecursive(portfolio.assetTypes, instrumentId);
}

public holdings FindHoldingsRecursive(
    IEnumerable<subAssetType> assetTypes,
    string instrumentId)
{
    if (assetTypes == null)
        return null;

    return assetTypes
      .Select(a => FindHoldingsRecursive(a, instrumentId))
      .FirstOrDefault(h => h != null);
}

public holdings FindHoldingsRecursive(
    subAssetType assetType, 
    string instrumentId)
{
    return 
        assetType.holdings.FirstOrDefault(h => h.instrumentIdentifier == instrumentId);
        ?? FindHoldingsRecursive(assetType.assetTypes, instrumentId);
}

This will do a depth-first search.

If you want a more generic solution to traversing a tree structure, I'd created these extension method for my own benefit:

public static class EnumerableExtensions
{
    public static IEnumerable<T> OrEmpty<T>(this IEnumerable<T> collection)
    {
        return collection ?? Enumerable.Empty<T>();
    }

    public static IEnumerable<T> Recurse<T>(
        this IEnumerable<T> collection, 
        Func<T, IEnumerable<T>> childrenSelector)
    {
        return collection.SelectMany(i => i.Recurse(childrenSelector));
    }

    public static IEnumerable<T> Recurse<T>(
        this T parent, 
        Func<T, IEnumerable<T>> childrenSelector)
    {
        yield return parent;
        var children = childrenSelector(parent).OrEmpty();
        foreach (var descendant in children.Recurse(childrenSelector))
        {
            yield return descendant;
        }
    }
}

This will let you do this:

var theHolding = portfolio.assetTypes
    .Recurse(a => a.assetTypes)
    .SelectMany(a => a.holdings.OrEmpty())
    .FirstOrDefault(h => h.instrumentIdentifier == "foo");