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How to address specific element in list

I want to create "list of list of list". It should be:
Group (has a list of Members)
Member (has a Name and list of Properties)
Property (has Name and Value)
What I want is to have a possibility to add Property into Member (specified by its name) inside defined Group. Someting like this:
membersgroup.AddNewMember(memberXYZ);
...
membersgroup.memberXYZ.AddProperty(nameXYZ, valueXYZ).
I have trouble achieving this using list... I found class Hashable, but I am not sure if this is usable... and cannot make it works too...
Thank for any suggestion :)

Well, I suggest you create a custom class instead of your approach. But otherwise you can use a Dictionary.
var properties = new Dictionary<string, string>();
properties.Add("Prop1", "Value");
var members = new Dictionary<string, Dictionary<string, string>>();
members.Add("Member1", properties);
var group = new Dictionary<string, Dictionary<string, Dictionary<string, string>>>();
group.Add("GroupName", members);

public class Group
{
public Group()
{
Members = new List<Member>();
}
public IEnumerable<Member> Members { get; set; }
}
public class Member
{
public Member()
{
Properties = new Dictionary<string, string>();
}
public string Name { get; set; }
IDictionary<string, string> Properties { get; set; }
}
The dictionary can take a key and a value, and the key should be unique.
You can also create a class property if you want to add another thing beside the name and the value

I would use indexers.
Here's a partial implementation:
class Group
{
private List<Member> _members;
public string this
{
get
{
return _members.Find(m => m.Name == value);
}
// You can also implement set here if you want...
}
}
class Member
{
private List<Property> _properties;
public string Name {get;set;}
public string this
{
get
{
return _properties.Find(m => m.Name == value);
}
}
}
class Property
{
public string Name {get;set;}
public string Value {get;set;}
}
And the usage:
var g = new Group();
g[memberName][propertyName].Value = someValue;
Note: This implementation is partial! it still needs constructor logic and any other logic you might need.

Likely the best solution is to use the C# class Dictionary - as suggested by zetawars, or a custom class - as suggested by Zohar Peled, or some mix of the two - as suggested by gandalf.
However, in order to use syntax similar to what is requested in the question...
membersgroup.AddNewMember(memberXYZ);
...
membersgroup.memberXYZ.AddProperty(nameXYZ, valueXYZ).
You can abuse ExpandoObject and Action, and do something awesome like this:
dynamic membersgroup = new ExpandoObject();
var getNewMemberObject = new Func<dynamic>(() =>
{
dynamic memberObject = new ExpandoObject();
var addPropertyAction = new Action<string, string>((propertyName, propertyValue) =>
{
((IDictionary<string, object>)memberObject).Add(propertyName, propertyValue);
});
memberObject.AddProperty = addPropertyAction;
return memberObject;
});
var addNewMemberAction = new Action<string>((memberName) =>
{
((IDictionary<string, object>)membersgroup).Add(memberName, getNewMemberObject());
});
membersgroup.AddNewMember = addNewMemberAction;
string memberXYZ = nameof(memberXYZ);
string nameXYZ = nameof(nameXYZ);
string valueXYZ = nameof(valueXYZ);
// look we did it!
membersgroup.AddNewMember(memberXYZ);
membersgroup.memberXYZ.AddProperty(nameXYZ, valueXYZ);
// and it actually works
var actualValue = membersgroup.memberXYZ.nameXYZ;
Console.WriteLine(actualValue); // "valueXYZ"
(for science of course)

Class to return different types - best option?

I need a class that can work with string properties to store data on a structured (class) list but at the same type to have a way to return an index that acts as the order I need to set up my data.
the class can be something like:
public class MyClass
{
public int int1 = 0;
public int int2 = 0;
public int int3 = 0;
public int int4 = 0;
public string string1 { get; set; }
public string string2 { get; set; }
public string string3 { get; set; }
public string string4 { get; set; }
}
then I can use my class to store the data in the class structured format:
string fileName = #"C:\Mylocation\MyTextFileToRead.txt"; //tab delimeted file
Encoding fileEncoding = Encoding.ASCII;
List<MyClass> myDataList = new List<MyClass>();
List<string> simpleData = File.ReadAllLines(fileName, fileEncoding).ToList();
MyClass index = new MyClass();
foreach (var line in simpleData)
{
var lineSplit = line.Split('\t');
MyClass myClassElement = new MyClass
{
string1 = lineSplit[index.int1],
string2 = lineSplit[index.int2],
string3 = lineSplit[index.int3],
string4 = lineSplit[index.int4],
};
myDataList.Add(myClassElement);
}
I use the index to map each property from the text file and then to store each filed values in the corresponding string property.
I do not wish to use object types and have the properties to return a string value and cast it as (int) for the index. I was advised not to use objects as much as possible.
The use of Const fields did not work for the index unless I use the type name of the class (instead an instance of the class), but I don't know if it helps or if this is a better programming option.
I'm not sure if there is a better way of doing this, but would be very welcome with relevant feedback.

To return two diffrent types from one function you can use the way that was introduce in C# 7.3
It works like this:
public (int, string) MyFunc()
{
//do something
return (VarThatInt, VarThatString);
}
//and in main class u call it like this:
(varInt, varString) = MyFunc();

using KeyValuePair to store one property and index, use list of KeyValuePair to store one line , and use dic Dictionary to store file .
List<int> orderIndexList = new List<int> { 2, 1, 4, 0 };
Dictionary<int, List<KeyValuePair<int, string>>> data = new Dictionary<int, List<KeyValuePair<int, string>>>();
int lineNumber = 0;
foreach (var line in simpleData)
{
var lineSplit = line.Split('\t');
List<KeyValuePair<int, string>> listLine = new List<KeyValuePair<int, string>>();
orderIndexList.ForEach(index => listLine.Add(new KeyValuePair<int, string>(index, lineSplit[index])));
data.Add(++lineNumber, listLine);
}
return data;

Return a class that has the two desired outputs. You can even return a third variable to tell the receiving code, which output to use.
public myClass{
String TextValue;
int NumberValue;
bool IsReturnString;
}
You would return an object of myClass.

Define list of objects. Get by specific field in object

How can we create a list of objects in C# and acces them by a specific field inside this object?
For example take this object:
class Section
{
public string Name { get; }
public long Size { get; }
public Section(string name, long size)
{
Name = name;
Size = size;
}
}
I would like to create a list of these objects which I can access by Section.Name.
I can create a dictionary like:
private static readonly Dictionary<string, Section> validSections = new Dictionary<string, Section>
{
{ "section-a", new Section("section-a", 1) },
{ "section-b", new Section("section-b", 2) },
{ "section-c", new Section("section-c", 3) },
{ "section-d", new Section("section-d", 4) },
};
But as you see, I have to declare the section name twice, which looks inelegant. Is there a more elegant way?

But as you see, I have to declare the section name twice, which looks
inelegant. Is there a more elegant way?
To avoid repetitve typing you can create dictionary from collection of sections via ToDictionary call:
private static readonly Dictionary<string, Section> validSections = new[] {
new Section("section-a", 1),
new Section("section-b", 2),
new Section("section-c", 3),
new Section("section-d", 4)
}.ToDictionary(s => s.Name);

If this is not time critical then you can use List<Section> list = new ArrayList<Section>(); and store data in it.
Later you can use LINQ to query based on name .where(x=>x.Name=="somename")

First of all your Model class can look like:
class Section
{
public string Name { get; set; }
public long Size { get; set; }
}
You don't need the Name twice so you can just create a list:
private static List<Section> myList = new List<Section>();
myList.add(new Section {Name = "section-a", Size = 1});
// do this for all the sections ...
Then as other answers suggest you can use LINQ:
myList.Single(s => s.Name == "section-a");
Will simply return the single element where the name is "section-a".
Read more about LINQ here: https://msdn.microsoft.com/en-us/library/bb308959.aspx

You could write a function that takes a list of sections and returns the corresponding dictionary. Something like:
public static Dictionary<string, Section> SectionDictionary(List<Section> sections) {
var dict = new Dictionary<string, Section>();
foreach (var section in sections)
dict.Add(section.Name, section);
return dict;
}

You can just access the elements using LINQ:
var list = ...;
var el = list.FirstOrDefault(o => o.Name = nameValue);
Or you can create a (collection) class that implements your own indexer / getter logic. E.g. (pseudocode)
public class MyCollection : Collection<Section>
{
public Section this[string nameValue]
{
get
{
return this.FirstOrDefault(o => o.Name == nameValue);
}
}
}
Then the usage is:
var coll = new MyCollection() ....;
var el = coll["Some name"];

ArrayList with Multiple Values c#

I am unsure whether this is possible with an ArrayList or a Dictionary or whether it would be something else, if so I wonder where you could point me in the right direction...
Can you have an ArrayList with Multiple Values i.e.
ArrayList weather = new ArrayList();
weather.Add("Sunny", "img/sunny.jpg");
weather.Add("Rain", "img/Rain.jpg);
To then assign to controls like below.
if (WeatherValue = 0)
{
Label1.Text = weather[0].ToString;
Image1.ImageUrl = weather[0].ToString;
}
Or can I do this with a Dictionary
Dictionary<string, string> dict = new Dictionary<string, string>();
dict.Add("Cloudy", "../img/icons/w0.png"); //[0]
dict.Add("Rain", "../img/icons/w1.png"); //[1]
Label1.Text = dict[0].VALUE1; //So this would get Cloudy
Image.ImageUrl = dict[0].VALUE2; //This would get ../img/w0.png
How do you call the values of a dictionary separately using [0], and [1] ? etc

There's no reason to still use ArrayList, use the System.Collections.Generic.List<T>-class. Then you keep compile time safety and you don't need to cast everything.
In this case you should create a custom class:
public class Weather
{
public double Degree { get; set; }
public string Name { get; set; }
public string IconPath { get; set; }
public override string ToString()
{
return Name;
}
}
Then you can use this readable and maintainable code:
List<Weather> weatherList = new List<Weather>();
weatherList.Add(new Weather { Name = "Sunny", IconPath = "img/sunny.jpg" });
weatherList.Add(new Weather { Name = "Rain", IconPath = "img/Rain.jpg" });
if (WeatherValue == 0) // whatever that is
{
Label1.Text = weatherList[0].Name;
Image1.ImageUrl = weatherList[0].IconPath;
}
Update: according to your edited question. A dictionary doesn't make much sense because you can't access it via index(it has no order) but only via key. Since that would be the weather-name you have to know it beforehand. But it seems that you don't have it.
So either loop all key-value pairs in the dictionary and use the key for the name and the value for the path or simply use a real class which would be much better.
If you don't want to create a class there's only one thing that comes to my mind, the Tuple:
List<Tuple<string, string>> weatherList = new List<string, string>();
weatherList.Add(Tuple.Create("Sunny", "img/sunny.jpg"));
weatherList.Add(Tuple.Create("Rain", "img/Rain.jpg"));
if (WeatherValue == 0) // whatever that is
{
Label1.Text = weatherList[0].Item1;
Image1.ImageUrl = weatherList[0].Item2;
}

You can use a Dictionary
Dictionary<string, string> weather = new Dictionary<string, string>();
values.Add("Sunny", "img/sunny.jpg");
values.Add("Rain", "img/Rain.jpg");
The simplest way to call element in a dictionnary is using foreach loop
foreach (var pair in weather )
{
Console.WriteLine("{0}, {1}",pair.Key,pair.Value);
}

Storing 2 columns into a List

How can I store data from 2 columns (from a database) in a List
List<string> _items = new List<string>();
Any help is appreciated

You create a class that will represent a row with 2 columns:
public class Foo
{
// obviously you find meaningful names of the 2 properties
public string Column1 { get; set; }
public string Column2 { get; set; }
}
and then you store in a List<Foo>:
List<Foo> _items = new List<Foo>();
_items.Add(new Foo { Column1 = "bar", Column2 = "baz" });

Use a tuple struct like KeyValuePair
List<KeyValuePair<string, string>> _items = new List<KeyValuePair<string, string>>();
_items.Add(new KeyValuePair<string, string>(foo, bar));

I would use a class
List<MyDataClass> _items = new List<MyDataClass>();
public class MyDataClass
{
public string Value1 { get; set; }
public string Value2 { get; set; }
}

You can either create a new class to hold the data, Or you could use the built in Tuple<> class. http://msdn.microsoft.com/en-us/library/system.tuple.aspx
Also if one of the columns contains a unique ID of some sort, you could also consider using a Dictionary<>.

It's about how to retrieve the data from the new two columns list
List<ListTwoColumns> JobIDAndJobName = new List<ListTwoColumns>();
for (int index = 0; index < JobIDAndJobName.Count;index++)
{
ListTwoColumns List = JobIDAndJobName[index];
if (List.Text == this.cbJob.Text)
{
JobID = List.ID;
}
}

I know this question is pretty old and by now you probably got your answer and have figured out what you need but I wanted to add something that might help someone in the future.
The best current answer is frankly from #csharptest.net but it has a serious performance drawback and so here is my approach a la his answer based on a suggestion to use Dictionary<TKey, TValue>
private Dictionary<string, string> _items = new Dictionary<string, string>();
// if you need to check to see if it exists already or not
private void AddToList(string one, string two)
{
if (!_items.ContainsKey(one))
_items.Add(one, two);
}
// you can simplify the add further
private void AddToList(string one, string two)
{
_items[one] = two;
// note if you try to add and it exists, it will throw exception,
// so alternatively you can wrap it in try/catch - dealer's choice
}

you can also make array of list
List<string> [] list= new List<String> [];
list[0]=new List<string>();
list[1]=new List<string>();
list[0].add("hello");
list[1].add("world");

You could do this:
List<IList<string>> cols = new List<IList<string>>();
You can set how many columns you want.
cols.Add(new List<string> { "", "", "","more","more","more","more","..." });