Is there a convenient way to remove a nested list from another list if it meets certain requirements? For example, say we have a collection of stops, and we decide to call each collection of stops a route. Each route is in list from. Then we decide to put each route into a list as well.
So now that we have a list of routes, someone decides that certain types of routes really shouldn't be included in the route list. How can I remove those routes? Here's some sample code:
Example Class
public class Stops
{
public Stops(int _param1, string _param2)
{
param1 = _param1;
param2 = _param2;
}
public int param1 { get; set; }
public string param2 { get; set; }
}
Create the Lists
List<List<Stops>> lstRoutes = new List<List<Stops>>();
List<Stops> lstStops = new List<Stops>();
List<Stops> lstMoreStops = new List<Stops>();
// Create some stops
for (int i = 0; i < 5; i++)
{
lstStops.Add(new Stops(i, "some text"));
}
lstRoutes.Add(lstStops);
// Create some more stops
for (int i = 5; i < 10; i++)
{
lstMoreStops.Add(new Stops(i, "some more text"));
}
lstRoutes.Add(lstMoreStops);
How can I remove any route from lstRoutes that has, say, any param1 value greater than 6?
The simplest way (which can be applicable to all enumerables, not just lists) would be:
lstRoutes = lstRoutes.Where(r => !r.Any(s => s.param1 > 6)).ToList();
The snippet above creates a new list, so copying will occur which means both the performance and memory usage will slightly suffer. The most efficient way would be not adding those items to the list in the first place.
The second most efficient way would be to remove items from the list instead of constructing a new one, so the memory usage wouldn't be affected as much:
lstRoutes.RemoveAll(r => r.Any(s => s.param1 > 6));
List<Stops> stop = lstRoutes.Find(delegate(List<Stops> stp) { return stp.param1 > 6; });
Related
using System;
using System.Collections.Generic;
using ConsoleApp3;
namespace ConsoleApp3
{
class Program
{
static void Main(string[] args)
{
Customers customers = new Customers();
List<Customers> names = new List<Customers>()
{
new Customers {Names = "Tanveer"},
new Customers {Names = "Nabila"},
new Customers {Names = "Suraj"}
};
foreach (int i = 0; i < names.Count; i++)
{
Console.WriteLine(customers.Names.Length);
}
}
class Customers
{
public string Names { get; set; }
}
}
}
I want to create the list of Customers and write it on the Console. But the Customers.Names is null. I am new to programming so please help.Thanks
First, let us fix up that naming. Naming is very important, but also one of the more annoying parts.
//Singular for the class
class Customer
{
//Also Singular, as this can only take 1 name
public string Name { get; set; }
}
//Plural, because it is a collection of Customer Instances.
List<Customer> Customers = new List<Customer>()
{
new Customer {Name = "Tanveer"},
new Customer {Name = "Nabila"},
new Customer {Name = "Suraj"}
};
Then you itterate over it using:
//Use a proper foreach, no need to deal with Indexes here
foreach (Customer current in Customers){
Console.WriteLine(current.Name);
}
If you do want to have a running counter, this is how the loop would look:
for(int i = 0; i < Customers.Count;i++){
//I you get any Exceptions, you want to split it up over 2 lines using a temporary variable
Console.WriteLine(Customers[i].Name);
}
What you had in your code was a bastardisation of for and foreach syntax, wich I doubt compiled.
Console.WriteLine(names[i].Names);
customers.Names is null because customers is an object which you haven't populated with any data, and has no obvious purpose. names is the actual list of customers with useful info in it.
names does not have a Names property directly either, though. The objects within the list do. So you need to refer to a specific object within the specific list.
And since you're in a loop for doing just that, names[i].Names.Length is no doubt what you intended.
N.B. However it needs to be a for rather than foreach in the loop definition - the syntax used with foreach is different. This shouldn't have compiled in order to allow you to even see the null output, so perhaps this is just a typo in your posted code.
for (int i = 0; i < names.Count; i++)
{
Console.WriteLine(names[i].Names.Length);
}
should be closer to what you need (although I'm not convinced you really are intending to print the length of each name...but that's up to you).
P.S. You should probably amend your naming convention so you've got Customer as the type and Name as the property. It's much more readable and comprehensible if they're singular rather than plural.
I have a list that is constantly being updated throughout my program. I would like to be able to compare the initial count and final count of my list after every update. The following is just a sample code (the original code is too lengthy) but it sufficiently captures the problem.
class Bot
{
public int ID { get; set; }
}
public class Program
{
public void Main()
{
List<Bot> InitialList = new List<Bot>();
List<Bot> FinalList = new List<Bot>();
for (int i = 0; i < 12345; i++)
{
Bot b = new Bot() {ID = i};
InitialList.Add(b);
}
FinalList = InitialList;
for (int i = 0; i < 12345; i++)
{
Bot b = new Bot() {ID = i};
FinalList.Add(b);
}
Console.Write($"Initial list has {InitialList.Count} bots");
Console.Write($"Final list has {FinalList.Count} bots");
}
}
Output:
Initial list has 24690 bots
Final list has 24690 bots
Expected for both lists to have 12345 bots.
What is correct way to copy the initial list so new set is not simply added to original?
To do what you seem to want to do, you want to copy the list rather than assign a new reference to the same list. So instead of
FinalList = InitialList;
Use
FinalList.AddRange(InitialList);
Basically what you had was two variables both referring to the same list. This way you have two different lists, one with the initial values and one with new values.
That said, you could also just store the count if that's all you want to do.
int initialCount = InitialList.Count;
FinalList = InitialList;
Although there's now no longer a reason to copy from one to the other if you already have the data you need.
I get the feeling you actually want to do more than what's stated in the question though, so the correct approach may change depending on what you actually want to do.
I want to sort a List Array on the basis of an array item.
I have a List Array of Strings as below:
List<String>[] MyProjects = new List<String>[20];
Through a loop, I have added five strings
(Id, Name, StartDate, EndDate, Status)
to each of the 20 projects from another detailed List source.
for(int i = 0; i<20; i++){
MyProjects[i].Add(DetailedProjectList.Id.ToString());
MyProjects[i].Add(DetailedProjectList.Name);
MyProjects[i].Add(DetailedProjectList.StartDate);
MyProjects[i].Add(DetailedProjectList.EndDate);
MyProjects[i].Add(DetailedProjectList.Status)}
The Status values are
"Slow", "Normal", "Fast", "Suspended" and "" for unknown status.
Based on Status, I want to sort MyProject List Array.
What I have done is that I have created another List as below
List<string> sortProjectsBy = new List<string>(){"Slow", "Normal", "Fast", "", "Suspended"};
I tried as below to sort, however unsuccessful.
MyProjects = MyProjects.OrderBy(x => sortProjectsBy.IndexOf(4));
Can anyone hint in the right direction. Thanks.
I suggest you to create class Project and then add all the fields inside it you need. It's much nicer and scalable in the future. Then create a List or an Array of projects and use the OrderBy() function to sort based on the field you want.
List<Project> projects = new List<>();
// Fill the list...
projects.OrderBy(project => project.Status);
The field Status has to be a primitive type or needs to implement the interface IComparable in order for the sorting to work. I suggest you add an enum for Status with int values.
First consider maybe to use Enum for status and put it in a different file lite (utils or something) - better to work like that.
enum Status {"Slow"=1, "Normal", "Fast", "", "Suspend"}
Now about the filtering you want to achieve do it like this (you need to tell which attribute of x you are referring to. In this case is status)
MyProjects = MyProjects.OrderBy(x => x.status == enum.Suspend);
Read about enums :
https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/enum
Read about lambda expressions :
https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/statements-expressions-operators/lambda-expressions
First of all, storing project details as List is not adivisable. You need to create a Custom Class to represent them.
For example,
public class DetailedProjectList
{
public string Name {get;set;}
public eStatus Status {get;set;}
// rest of properties
}
Then You can use
var result = MyProjects.OrderBy(x=> sortProjectsBy.IndexOf(x.Status));
For example
List<string> sortProjectsBy = new List<string>(){"Slow", "Normal", "Fast", "", "Suspended"};
var MyProjects= new List<DetailedProjectList>{
new DetailedProjectList{Name="abc1", Status="Fast"},
new DetailedProjectList{Name="abc2", Status="Normal"},
new DetailedProjectList{Name="abc3", Status="Slow"},
};
var result = MyProjects.OrderBy(x=> sortProjectsBy.IndexOf(x.Status));
Output
abc3 Slow
abc2 Normal
abc1 Fast
A better approach thought would be to use Enum to represent Status.
public enum eStatus
{
Slow,
Normal,
Fast,
Unknown,
Suspended
}
Then your code can be simplified as
var MyProjects= new List<DetailedProjectList>{
new DetailedProjectList{Name="abc1", Status=eStatus.Fast},
new DetailedProjectList{Name="abc2", Status=eStatus.Normal},
new DetailedProjectList{Name="abc3", Status=eStatus.Slow},
};
var result = MyProjects.OrderBy(x=> x.Status);
Ok so you have a collection of 20 items. Based on them you need to create a list of strings(20 DetailedProjectList items).
What you can do to solve your problem is to SORT YOUR COLLECTION before you create your list of strings. In this way your list of strings will be sorted.
But your code is not optimal at all. So you should concider optimization on many levels.
Lets say you have ProjectDetail class as follow:
private class ProjectDetail
{
public int Id {get;set;}
public string Name {get;set;}
DateTime StartDate {get;set;} = DateTime.Now;
DateTime EndDate {get;set;} = DateTime.Now;
public string Status {get;set;}
public string toString => $"{Id} - {Name} - {StartDate} - {EndDate} - {Status}";
}
Notice that I have added a toString attribute to make things easier, and I also have added default values.
Then your program could be like:
static void Main(string[] args)
{
var projectDetails = MockProjectItems();
Console.WriteLine("Before sortig:");
foreach (var item in projectDetails)
{
Console.WriteLine(item.toString);
}
var myProjects = projectDetails.OrderBy(p => p.Status).Select(p => p.toString);
Console.WriteLine("\n\nAfter sorting:");
foreach (var item in myProjects)
{
Console.WriteLine(item);
}
}
where the helper method is
private static List<ProjectDetail> MockProjectItems()
{
var items = new List<ProjectDetail>(20);
for(int i = 0; i < 20 ; i += 4){
items.Add(new ProjectDetail{Id = i, Name = "RandomName "+i, Status = "Slow"});
items.Add(new ProjectDetail{Id = i+1, Name = "RandomName "+(i+1), Status = "Normal"});
items.Add(new ProjectDetail{Id = i+2, Name = "RandomName "+(i+2), Status = "Fast"});
items.Add(new ProjectDetail{Id = i+3, Name = "RandomName "+(i+3), Status = "Suspended"});
}
return items;
}
Then your program should print the following:
I'm really new to programming, so take this with a grain of salt.
I've made 2 arrays that correspond to eachother; One is a Name array and one is a Phone Number array. The idea is that the spot [1] in NameArray corresponds to spot [1] in the PhoneArray. In other words, I need to keep these 'pairings' in tact.
I'm trying to make a function that deletes one of the spots in the array, and shifts everything down one, as to fill the space left empty by the deleted element.
namearray = namearray.Where(f => f != iNum).ToArray();
is what I've tried, with iNum being the number corresponding to the element marked for deletion in the array.
I've also tried converting it to a list, removing the item, then array-ing it again.
var namelist = namearray.ToList();
var phonelist = phonearray.ToList();
namelist.Remove(txtName.Text);
phonelist.Remove(txtPhone.Text);
namearray = namelist.ToArray();
phonearray = phonelist.ToArray();
lbName.Items.Clear();
lbPhone.Items.Clear();
lbName.Items.AddRange(namearray);
lbPhone.Items.AddRange(phonearray);
with txtName.Text and txtPhone.Text being the strings for deletion in the corresponding list boxes.
Can someone suggest a better way to do it / What I'm doing wrong / How to fix?
Thanks guys
-Zack
A better way would be to have an array of a class that contains a Name and Phone Number object:
public class PersonData
{
public string Name { get; set; }
public string Phone { get; set; }
}
public PersonData[] data;
That way, instead of keeping two arrays in sync, it's one array with all the appropriate data.
Try a loop through both arrays, moving the values of each down an index each time.
Start the loop at the index of the value you want to delete. So you would find the IndexOf(T) the value you want, storing it as deleteIndex and run the loop starting from that index.
When you hit the end of the array, set the last value as null or string.Empty (depending what value type the array holds).
A bit like this:
var deleteIndex = namearray.IndexOf("TheStringYouWantToDelete");
for (int i = deleteIndex; i < namearray.Length; i++)
{
if (i == namearray.Length - 1) // The "last" item in the array.
{
namearray[i] = string.Empty; // Or null, or your chosen "empty" value.
phonearray[i] = string.Empty; // Or null, or your chosen "empty" value.
}
else
{
namearray[i] = namearray[i+1];
phonearray[i] = phonearray[i+1];
}
}
This will work for deleting and moving values 'down' in index.
You could also rewrite the code for moving them the other way, as it would work similarly.
Reordering them completely? Different ball game...
Hope this helps.
If the namearray and phonearray contain strings and you know the index of the element to remove (iNum) then you need to use the overload of the Where extension that takes a second parameter, the index of the current element in the evaluation
namearray = namearray.Where((x, y) => y != iNum).ToArray();
However the suggestion to use classes for your task is the correct one. Namearray and Phonearray (and whatever else you need to handle in future) are to be thought as properties of a Person class and instead of using arrays use a List<Person>
public class Person
{
public string FirstName {get; set;}
public string LastName {get; set;}
public string Phone {get; set;}
}
List<Person> people = new List<Person>()
{
{new Person() {FirstName="Steve", LastName="OHara", Phone="123456"}},
{new Person() {FirstName="Mark", LastName="Noname", Phone="789012"}}
};
In this scenarion removing an item knowing the LastName could be written as
people = people.Where(x => x.LastName != "OHara").ToList();
(or as before using the index in the list of the element to remove)
people = people.Where((x, y) => y != iNum).ToArray();
The other answers provide some better design suggestions, but if you're using ListBoxes and want to stick with arrays, you can do this to synchronize them:
int idx = lbName.Items.IndexOf(txtName.Text);
if (idx > -1)
{
lbName.Items.RemoveAt(idx);
lbPhone.Items.RemoveAt(idx);
}
namearray = lbName.Items.Cast<string>().ToArray<string>();
phonearray = lbPhone.Items.Cast<string>().ToArray<string>();
Use a dictionary instead.
Dictionary<string, string> phoneBook = new Dictionary<string, string>();
phoneBook["Foo"] = "1234567890";
phoneBook["Bar"] = "0987654321";
phoneBook.Remove("Bar");
Using a semi-complex structure, I am trying to 'combine' several objects into one using the Linq Aggregate method (though if there is a better way, I am open to ideas).
Here is my basic class design.
class Aspect {
string Name { get; set; }
}
class Arrangement {
Aspect Aspect { get; set; }
IList<Aperture> Apertures { get; set; }
IList<Step> Steps { get; set; }
}
class Step {
int Rank { get; set; }
int Required { get; set; }
}
class Aperture {
string Name { get; set; }
int Size { get; set; }
}
Basically, I am trying to aggregate the entire hierarchy of an IEnumerable<Arrangement> and keep everything on the base level, but where things can appropriately overwrite, I want to overwrite them.
Update
I want to get all Arrangements that share the same Aspect.Name, and get a complete list of Steps, overwriting lower level Steps where higher level Arrangements have the same Rank with a different Required value.
So take for instance...
var list = new List<Arrangement>{
new Arrangement{
Aspect = Aspects.Named("One"),
Steps = new List<Step>{
new Step {
Rank = 1,
Required = 2
},
new Step {
Rank = 2,
Required = 4
}
}
},
new Arrangement{
Aspect = Aspects.Named("One"),
Steps = new List<Step>{
new Step {
Rank = 1,
Required = 3
}
}
}
}
When aggregated properly, it should come out to look like ...
Arrangement
- Aspect
- Name : One
- Steps
- Rank : 1
- Required : 3
- Rank : 2
- Required : 4
I have attempted to use Distinct and Aggregate and it just isn't getting me anywhere. I keep ending up not getting one list or the other. Can anyone help with this?
Update
Here is an example of my current aggregation.
public static Layouts.Template Aggregate(this IList<Layouts.Template> source) {
return source.Aggregate(
source.First(),
(current, next) => new Layouts.Template {
Apertures = (current.Apertures.Concat(next.Apertures).Distinct().ToList()),
Arrangements = (current.Arrangements.Concat(next.Arrangements).Distinct().ToList()),
Pages = (current.Pages.Concat(next.Pages).Distinct().ToList())
});
}
My problem is that I'm having a lot of trouble wrapping my head around how to do this at all, much less in one expression. I'm not unwilling to use multiple methods, but if I could encapsulate it all, it would be really useful. I am fascinated by LINQ in general and I really want to get my head around this.
Update 2
The other collection, Apertures, will work in a similar manner, but it is unrelated to the Steps. Simply two different arrays I must do the same thing to, but they have nothing in common with one another. Learning how to do this with one will give me the knowledge to do it with the other.
If there's no correlation between steps and apertures you can do this:
var result = new Arrangement{
Steps = list.SelectMany(arrangement => arrangment.Steps)
.GroupBy(step => step.Rank)
.Select(l => l.Last())
.OrderBy(step => step.Rank)
.ToList()),
}
If there is you'll need to combine the two somehow. If steps index into apertures then you can use something similar.
After your updates:
var query = arrangements
.GroupBy(a => a.Aspect.Name)
.Select(g =>
new Arrangement
{
Steps = ga.SelectMany(a => a.Steps)
.GroupBy(s => s.Rank)
.Select(gs => gs.Last()),
Aspect = ga.First().Aspect
});
This will create output as in your example.
Now, how to merge it with your current aggregation method? As to my understanging, you want to create one big layout from all current layout contents (including arrangements, pages, etc)?
You don't need aggregate at all, just split it into 3 LINQ queries:
// get all arrangements object from all layouts [flattening with SelectMany]
var arrangements = source.SelectMany(s => s.Arrangements);
// and filter them
var filteredArrangements = // enter larger query from above here
// repeat the same for Apertures and Pages
...
// and return single object
return new Layouts.Template
{
Apertures = filteredApertures,
Arrangements = filteredArrangements,
Pages = filteredPages
};
I assume this isn't the complete solution that you want:
private static Arrangement Accumulate(IEnumerable<Arrangement> arrangements)
{
var stepsByRank = new Dictionary<int, Step>();
foreach (var arrn in arrangements)
foreach (var step in arrn.Steps)
stepsByRank[step.Rank] = step;
return new Arrangement { Steps = stepsByRank.Values.ToArray() };
}
What's missing from this? How else do you want to "aggregate" the arrangements and steps? (edit: after reading your comment, maybe this actually is what you want.)