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C# Recursively loop over object and return all children [duplicate]

This question already has answers here:
How to flatten tree via LINQ?
(15 answers)
Closed 6 months ago.
I've the following class, which contains some info about the object it also has a list of same object and hierarchy goes on. This is my class:
public class Category
{
public List<Category>? children { get; set; }
public bool var { get; set; }
public string? name { get; set; }
public bool leaf { get; set; }
public int category_id { get; set; }
}
I have a list List<Category> categories; I want to loop over the list and go deep down in every children and create this new object:
public class DBCategory
{
public string? CategoryId { get; set; }
public string? CategoryName { get; set; }
public string? CategoryParentId { get; set; }
}
I have tried to loop over my list and then call function recursively but I'm also stuck there because children isn't a category class but a list of categories so the function fails to accept parameter in if clause:
foreach (var category in categories)
{
CreateDBCategory(category);
}
DBCategory CreateDBCategory(Category category)
{
DBCategory dBCategory = new DBCategory();
if (category.children.Count > 0)
{
return CreateDBCategory(category.children);
}
return dBCategory;
}
I have also tried to reach most bottom child by this, but this code says not all paths return a value.
DBCategory testFunction(List<Category> categories)
{
foreach (var category in categories)
{
if (category.children.Count > 0)
{
return testFunction(category.children);
}
else
{
return category;
}
}
}

One of the common ways to handle such cases is to have the List to be filled passed as an argument to the method. E.g.:
List<DBCategory> dbCategories = new();
foreach (var category in categories)
{
CreateDBCategory(category, dbCategories);
}
void CreateDBCategory(Category category, List<DBCategory> dbCategories)
{
DBCategory dbCategory = new DBCategory();
// Fill dbCategory
dBCategories.Add(dbCategory);
if (category.children != null)
{
// recurse over all children categories and add them to the list
foreach (var child in category.children)
{
CreateDBCategory(child, dbCategories);
}
}
}
It could be argued that this solution does not fit the functional paradigm as it has side effects (modifying the passed in List), so an alternative, more functional approach would be to return a list from the recursive method, e.g.:
List<DBCategory> dbCategories = new();
foreach (var category in categories)
{
dbCategories.AddRange(CreateDBCategory(category));
}
IEnumerable<DBCategory> CreateDBCategory(Category category)
{
List<DBCategory> dbCategories = new();
DBCategory dbCategory = new DBCategory();
// Fill dbCategory
dbCategories.Add(dbCategory);
if (category.children != null)
{
// recurse over all children categories and add them to the list
foreach (var child in category.children)
{
dbCategories.AddRange(CreateDBCategory(child));
}
}
return dbCategories;
}
This does however perform a lot more allocations, so in some cases it can perform slower than the first approach

Noted that this is untested, but it should work.
IEnumerable<DBCategory> FlattenCategories(IEnumerable<Category> categories, int parentId)
{
DBCategory selector(Category cat, int pid) =>
return categories
.Select(c => new DBCategory {
CategoryId = cat.category_id,
CategoryName = cat.name,
CategoryParentId = pid,
})
.Concat(categories.SelectMany(
c => FlattenCategories(c.children, c.category_id)
);
}
Just call FlattenCategories(categories).ToList(); to get List<DBCategory>

From here, A generic solution.
public static IEnumerable<T> Traverse<T>(
this T root,
Func<T, IEnumerable<T>> childrenSelector)
{
ArgumentNullException.ThrowIfNull(childrenSelector);
var stack = new Stack<T>();
stack.Push(root);
while(stack.Count > 0)
{
var current = stack.Pop();
yield return current;
foreach(var child in childrenSelector(current))
{
stack.Push(child);
}
}
}
So you can do this,
foreach(var category in root.Traverse(c => c.Children))
{
...
}
or some LINQ. The beauty is, it won't allocate more memory than your biggest leaf collection and won't have a stack overflow for deep trees.

Try following :
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication40
{
class Program
{
static void Main(string[] args)
{
Category root = new Category()
{
children = new List<Category>() {
new Category() {
children = new List<Category>() {
new Category() {
var = true,
name = "2A",
leaf = true,
category_id = 21
},
new Category() {
var = true,
name = "2B",
leaf = true,
category_id = 22
}
},
var = true,
name = "1A",
leaf = false,
category_id = 1
},
new Category() {
children = new List<Category>() {
new Category() {
var = true,
name = "2C",
leaf = true,
category_id = 23
},
new Category() {
var = true,
name = "2D",
leaf = true,
category_id = 24
}
},
var = true,
name = "1B",
leaf = false,
category_id = 2
},
},
category_id = 0,
name = "root",
leaf = false,
var = true
};
List<DBCategory> children = DBCategory.GetChildren(root,null);
}
}
public class Category
{
public List<Category> children { get; set; }
public bool var { get; set; }
public string name { get; set; }
public bool leaf { get; set; }
public int category_id { get; set; }
}
public class DBCategory
{
public int? CategoryId { get; set; }
public string CategoryName { get; set; }
public int? CategoryParentId { get; set; }
public static List<DBCategory> GetChildren(Category catgory, int? parentId)
{
List<DBCategory> results = new List<DBCategory>() { new DBCategory() {
CategoryId = catgory.category_id,
CategoryName = catgory.name,
CategoryParentId = parentId
}};
if (catgory.children != null)
{
foreach (Category child in catgory.children)
{
results.AddRange(GetChildren(child, catgory.category_id));
}
}
return results;
}
}
}

How to convert Model List to Json

I am trying to create an json data similar to this https://cdn.jsdelivr.net/gh/highcharts/highcharts#v7.0.0/samples/data/world-mortality.json
The current output I am getting is like this. The model name is being displayed and child does not seems to work. is t possible to remove the model field name on the serialize?
[{Name:"ABC",
Firstchild:[{Name:"AIR IMPORT",
Secondchild:[{NAME:"SCMBOA00052997",VALUE:69.7500},
{NAME:"SH123",VALUE:-100.0000},
{NAME:"SH456",VALUE:50.0000},
{NAME:"SH789",VALUE:150.0000}]
}]
}{Name:"DEF",
Firstchild:[{Name:"AIR IMPORT",
Secondchild:[{NAME:"SCMBOA00052997",VALUE:69.7500},
{NAME:"SH111",VALUE:-10.0000},
{NAME:"SH222",VALUE:80.0000},
{NAME:"SH333",VALUE:160.0000}]
}]
}]
What I need is like this
{
"ABC": {
"AIR IMPORT":{
"SH123": -100.0000,
"SH456": 50.0000,
"SH789": 150.0000
}
},
"DEF": {
"AIR IMPORT":{
"SH111": -10.0000,
"SH222": 80.0000,
"SH333": 160.0000
}
}
}
MODEL
public class ParentTreemap
{
public string Name { get; set; }
public List<FirstChildTreemap> Firstchild { get; set; }
}
public class FirstChildTreemap
{
public string Name { get; set; }
public List<SecondChildTreemap> Secondchild { get; set; }
}
public class SecondChildTreemap
{
[JsonProperty]
public string Name { get; set; }
[JsonProperty]
public decimal Value { get; set; }
}
Controller
var parent = treemaplist.Where(s => s.Parent == 0);
List<ParentTreemap> plist = new List<ParentTreemap>();
foreach (var item in parent)
{
var firstchild = treemaplist.Where(s => s.Parent == item.Id && s.Value==0);
List<FirstChildTreemap> flist = new List<FirstChildTreemap>();
foreach (var fitem in firstchild)
{
var secondchild = treemaplist.Where(s => s.Parent == fitem.Id && s.Value!=0);
List<SecondChildTreemap> slist = new List<SecondChildTreemap>();
foreach (var sitem in secondchild)
{
SecondChildTreemap model = new SecondChildTreemap();
model.Name = sitem.Name;
model.Value = sitem.Value;
slist.Add(model);
}
FirstChildTreemap child = new FirstChildTreemap();
child.Name = fitem.Name;
child.Secondchild = slist;
flist.Add(child);
}
ParentTreemap pmodel = new ParentTreemap();
pmodel.Name = item.Name;
pmodel.Firstchild = flist;
plist.Add(pmodel);
}
var stringWriter = new StringWriter();
var serializer = new JsonSerializer();
using (var writer = new JsonTextWriter(stringWriter))
{
writer.QuoteName = false;
serializer.Serialize(writer, plist);
}
ViewData["result"] = stringWriter;

Converted JSON to classes, how to set values

I have pasted JSON in to my C# console application, so it produces classes like so :
public class Rootobject
{
public Id id { get; set; }
}
public class Id
{
public Identifier Identifier { get; set; }
}
public class Identifier
{
public Id1 id { get; set; }
public Type type { get; set; }
}
public class Id1
{
public string IdentifierString { get; set; }
}
public class Type
{
public string IdentifierType { get; set; }
}
I wish to set the values of identifierString and identifierType like so :
var node = new Rootobject();
node.id.Identifier.id.IdentifierString = "testId";
node.id.Identifier.type.IdentifierType = "idType";
However, I get an 'Object reference not set to an instance of an object' error.

you should write:
var node = new Rootobject();
node.id = new Id();
node.id.Identifier = new Identifier();
node.id.Identifier.id = new Id1();
node.id.Identifier.type = new Type();
node.id.Identifier.id.IdentifierString = "testId";
node.id.Identifier.type.IdentifierType = "idType";
or even better:
var node = new Rootobject
{
id = new Id
{
Identifier = new Identifier
{
id = new Id1 { IdentifierString = "id" },
type = new Type { IdentifierType = "type" },
}
}
};
You are missing creation of objects, they are nulls

Or version which compile :)
var node = new RootObject
{
id = new Id
{
Identifier = new Identifier
{
id = new Id1 { IdentifierString = "id" },
type = new Type { IdentifierType = "type" },
}
}
};

C# - Adding data to list inside list

How can I add the following data on the table into a list called Vehicles?
public class criterias
{
public double values { get; set; }
public double time { get; set; }
}
public class movChannels
{
public string name { get; set; }
public IList<criterias> criteria = new List<criterias>();
}
public class stepsList
{
public string steps { get; set; }
public IList<movChannels> stepChannelsCriteria = new List<movChannels>();
}
public class vehicles
{
public int vehID { get; set; }
public string vehDescription { get; set; }
public IList<stepsList> vehValCriteria = new List<stepsList>();
}
Now, how can I add the data that I have in the table shown into a list called Vehicles? I will create other vehicles later...

You had several bad decisions, some were design flaws and some were minor C# naming convention violations.
Couple of worth mentions flaws:
vehID should have been a string and not int (Example "XPT")
Movment has Name, Value and Time. It doesn't have a list of Values and Times.
Creation:
List<Vehicle> vehicles = new List<Vehicle>();
Vehicle vehicle = new Vehicle()
{
Id = "XPT",
Description = "Average Car",
Steps = new List<Step>()
{
new Step() {
Name = "move car",
Movements = new List<Movement>()
{
new Movement("engage 1st gear", 1, 1),
new Movement("reach 10kph", 10, 5),
new Movement("maintain 10kph", 10, 12),
}
},
new Step() {
Name = "stop car",
Movements = new List<Movement>()
{
new Movement("reach 0kph", 10, 4),
new Movement("put in neutral", 0, 1),
new Movement("turn off vehicle", 0, 0),
}
}
}
};
vehicles.Add(vehicle);
Entities:
public class Movement
{
public string Name { get; set; }
public double Values { get; private set; }
public double Time { get; private set; }
public Movement(string name, double values, double time)
{
Name = name;
Values = values;
Time = time;
}
}
public class Step
{
public string Name { get; set; }
public IList<Movement> Movements { get; set; }
}
public class Vehicle
{
public string Id { get; set; } // Should be changed to string
public string Description { get; set; }
public IList<Step> Steps { get; set; }
}

You should create your classes like the following:
public class criterias
{
public double values { get; set; }
public double time { get; set; }
}
public class movChannels
{
public movChannels
{
criteria = new List<criterias>();
}
public string name { get; set; }
public IList<criterias> criteria { get; set; }
}
public class stepsList
{
public stepsList
{
stepChannelsCriteria = new List<movChannels>();
}
public string steps { get; set; }
public IList<movChannels> stepChannelsCriteria { get; set; }
}
public class vehicles
{
public vehicles
{
vehValCriteria = new List<stepsList>();
}
public int vehID { get; set; }
public string vehDescription { get; set; }
public IList<stepsList> vehValCriteria { get; set; }
public movChannels movments { get; set; }
}

What about that?
public class VehiclesViewModel
{
public List<vehicles> Vehicles { get; private set; }
public void Initalize()
{
this.Vehicles = new List<vehicles>();
var vehicle = new vehicles
{
vehID = 1,
vehDescription = "firstDescription",
};
var stepsList = new stepsList
{
steps = "firstStep",
};
var movChannel = new movChannels
{
name = "firstChannel",
};
var criteria = new criterias
{
values = 0.5,
time = 0.5
};
movChannel.criteria.Add(criteria);
stepsList.stepChannelsCriteria.Add(movChannel);
vehicle.vehValCriteria.Add(stepsList);
this.Vehicles.Add(vehicle);
}
}

it seems in your table the VehicleId is of type string. Make sure your VehicleId property in Vehicle class also matches the same.
You can use the collection initializers to set the values of child objects like this way:
var data = new vehicles()
{
vehID = 1,
vehDescription = "Average Car",
vehValCriteria = new List<stepsList>()
{
new stepsList()
{
steps = "Move car",
stepChannelsCriteria = new List<movChannels>()
{
new movChannels()
{
name = "engage firstgear",
criteria = new List<criterias>()
{
new criterias()
{
values = 1,
time = 1
},
}
},
new movChannels()
{
name = "reach 10kph",
criteria = new List<criterias>()
{
new criterias()
{
values = 10,
time = 5
},
}
},
new movChannels()
{
name = "maintain 10kph",
criteria = new List<criterias>()
{
new criterias()
{
values = 10,
time = 12
},
}
}
}
},
new stepsList()
{
steps = "stop car",
stepChannelsCriteria = new List<movChannels>()
{
new movChannels()
{
name = "reach okph",
criteria = new List<criterias>()
{
new criterias()
{
values = 10,
time = 4
},
}
},
new movChannels()
{
name = "put in neutral",
criteria = new List<criterias>()
{
new criterias()
{
values = 0,
time = 1
},
}
},
new movChannels()
{
name = "turn off vehicle",
criteria = new List<criterias>()
{
new criterias()
{
values = 0,
time = 0
},
}
}
}
}
}
};

You can fill your list by moving from top to bottom, like
Create Criterias List then Create movChannel object and add that list
to Criterias object and so on
However if you want to avoid this way, there is another way. If you are using Linq To List then follow this
Get a simple flat object to a list object
var TableData = db.Tablename.Tolist();
Then fill your own object like this
Vehicles finalList = TableData.Select(a => new Vehicles()
{
vehID = a.Id,
vehDescription = a.des,
vehValCriteria = TableData.Where(b => b.StepslistId == a.StepslistId)
.Select(c => new StepsList()
{
steps = c.Steps,
stepChannelsCriteria = TableData.Where(d => d.channelId == c.channelId)
.select(e => new MovChannels()
{
name = e.name,
criteria = TableData.Where(f => f.criteriasId = e.criteriasId)
.Select(g => new Criterias()
{
values = g.Values,
time = g.Time
}).ToList()
}).ToList()
}).ToList()
}).ToList();
This is standard way to fill list within list

Group items by content of list

Lets say i got a something like this:
public class Subscriber{
public string Name {get; set;}
}
public class SomeData{
public string Content {get; set;}
}
public class InputData {
public Subscriber Subscribers { get; set; }
public IEnumerable<SomeData> DataItems { get; set; }
}
public class QueueItem {
public IEnumerable<Subscriber> Subscribers { get; set; }
public IEnumerable<SomeData> DataItems { get; set; }
}
Now lets say i get a List<InputData> full of "Subscribers" with a list of data for each subscriber.
Now i want to compare the list of data of each subscriber, and end up with a List<QueueItem>, where if 2 subscribers have the same set of data items, they would be 1 QueueItem.
Hope this makes sense

The technique is using EqualityComparer with Enumerable.SequenceEqual()
public class Subscriber
{
public string Name { get; set; }
// For compare
public override bool Equals(object obj) { return string.Equals(this.Name, ((Subscriber)obj).Name); }
public override int GetHashCode() { return this.Name.GetHashCode(); }
}
public class SomeData
{
public string Content { get; set; }
// For compare
public override bool Equals(object obj) { return string.Equals(this.Content, ((SomeData)obj).Content); }
public override int GetHashCode() { return this.Content.GetHashCode(); }
}
public class InputData
{
public Subscriber Subscribers { get; set; }
public IEnumerable<SomeData> DataItems { get; set; }
// Should always initialize an empty collection
public InputData() { this.DataItems = new List<SomeData>(); }
}
public class QueueItem
{
public IEnumerable<Subscriber> Subscribers { get; set; }
public IEnumerable<SomeData> DataItems { get; set; }
// Should always initialize an empty collection
public QueueItem() { this.Subscribers = new List<Subscriber>(); this.DataItems = new List<SomeData>(); }
}
public class DataItemsEqualityComparer : EqualityComparer<IEnumerable<SomeData>>
{
public override bool Equals(IEnumerable<SomeData> x, IEnumerable<SomeData> y)
{
return Enumerable.SequenceEqual(x.OrderBy(i => i.Content), y.OrderBy(i => i.Content));
}
public override int GetHashCode(IEnumerable<SomeData> obj)
{
return obj.Select(i => i.GetHashCode()).Sum().GetHashCode();
}
}
Usage
var data = new List<InputData>();
var fruits = new[] { new SomeData() { Content = "apple" }, new SomeData() { Content = "pear"} };
var colors = new[] { new SomeData() { Content = "red" }, new SomeData() { Content = "blue" }, new SomeData() { Content = "green" } };
data.Add(new InputData() { Subscribers = new Subscriber() { Name = "Alice" }, DataItems = new List<SomeData>(fruits) });
data.Add(new InputData() { Subscribers = new Subscriber() { Name = "Bob" }, DataItems = new List<SomeData>(colors) });
data.Add(new InputData() { Subscribers = new Subscriber() { Name = "Charlie" }, DataItems = new List<SomeData>(fruits) });
List<QueueItem> groupedData = data.GroupBy(
i => i.DataItems,
i => i.Subscribers,
new DataItemsEqualityComparer())
.Select(i => new QueueItem() { Subscribers = i, DataItems = i.Key }).ToList();
Result
QueueItem :
Subscribers:
- Alice
- Charlie
Data:
- apple
- pear
QueueItem :
Subscribers:
- Bob
Data:
- red
- blue
- green

var queue = Dictionary(Subscriber, List<SomeData>);
//And lets just for example add some data
var items1 = new List<SomeData>();
items1.Add(new SomeData("test"));
items1.Add(new SomeData("test2"));
var items2 = new List<SomeData>();
items2.Add(new SomeData("test"));
queue.Add(new Subscriber("Peter"), items1);
queue.Add(new Subscriber("Luke"), items1);
queue.Add(new Subscriber("Anna"), items2);
Dictionary<Subscriber, List<SomeData>> myDictionary = queue
.GroupBy(o => o.PropertyName)
.ToDictionary(g => g.Key, g => g.ToList());