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I'm struggling to get a foreach loop working to loop through each element of a LinkedList

Im trying to do a Depth first traversal on graph node but I cant get my for each loop to loop correctly
Here is the code for doing the search
The foreach line is the problem
public void DepthFirstTraverse(T startID, ref List<T> visited)
{
LinkedList<T> adj;
Stack<T> toVisit = new Stack<T>();
GraphNode<T> current = new GraphNode<T>(startID);
toVisit.Push(startID);
while (toVisit.Count != 0)
{
current.ID = toVisit.Peek();
toVisit.Pop();
visited.Add(current.ID);
Console.WriteLine(current.GetAdjList());
foreach(T n in current.GetAdjList())
{
Console.WriteLine("Loop working");
if(toVisit.Contains(n)==false && visited.Contains(n)==true)
{
toVisit.Push(n);
}
}
}
}
Here is the graphnode code, it calls the getadjlist and should loop through for each element in that list, currently it doesnt loop at all
public class GraphNode
{
private T id; // data stored in the node (“id” of the node).
private LinkedList adjList; // adjacent list of the node
// constructor
public GraphNode(T id)
{
this.id = id;
adjList = new LinkedList<T>();
}
// set and get the data stored in the node
public T ID
{
set { id = value; }
get { return id; }
}
//add a directed edge from “this” node to the node "to”
public void AddEdge(GraphNode<T> to)
{
adjList.AddFirst(to.ID);
}
// returns the adjacent list of the node
public LinkedList<T> GetAdjList()
{
return adjList;
}
}

Simple List Merge C# (Without Generics)

I have created a simple list class from scratch. This is for a class assignment that I have been working on for about a week - very new to lists. We can not use generics so trying to research my question below has not been fruitful. Although I did get to watch 7 tutorials on youtube by BetterCoder and I found some stuff in my book but nothing with an example of "merging".
I have three classes - my node, my list, and my program. In my list class, I am working on building a Merge() method which eventually will compare the data in the two lists and merge them into an ordered list.
Right now for some reason my Merge method - which is very basic to help me understand what is happening - is not working correctly. It has both lists passed to it, and is adding the data from listTwo to listOne BUT for some reason when it's printing to the console the second Node's Data shows twice :
EX: 1 -> 2 -> 2
instead of printing the head (1), the next (2) and then the next (3) which it should be.
EX: 1 -> 2 -> 3
In the program class I have proven with a write line that (listOne.firstNode.Next.Next.Data) = 3 . Which it should be.
Can someone help me figure out if the nodes in list one aren't pointing to each other correctly or whatever is going on?
My Merge Method must be passed both list objects (listOne and listTwo) and eventually I need to make those passed as references but I haven't figured that out quite yet and will focus on that later I suppose.
namespace LinkedList
{
//This is my Node Class
class Node
{
public object Data { get; set; }
public Node Next { get; set; }
public Node(object dataValue) : this(dataValue, null) { }
public Node(object dataValue, Node nextNode)
{
Data = dataValue;
Next = nextNode;
}
}
//This is my List Class
class List
{
public Node firstNode;
public int count;
public List()
{
firstNode = null;
}
public bool Empty
{
get { return this.count == 0; }
}
public int Count
{
get { return this.count; }
}
public object Add(int index, object o)
{
if (index < 0)
throw new ArgumentOutOfRangeException("Index: " + index);
if (index > count)
index = count;
Node current = this.firstNode;
if (this.Empty || index == 0)
{
this.firstNode = new Node(o, this.firstNode);
}
else
{
for (int i = 0; i < index - 1; i++)
current = current.Next;
current.Next = new Node(o, current.Next);
}
count++;
return o;
}
public object Add(object o)
{
return this.Add(count, o);
}
public object Merge(List a, List b)
{
a.Add(b.firstNode.Data);
return a;
}
public void Print()
{
while (this.count > 0)
{
Console.Write(firstNode.Data + "->");
if(firstNode.Next != null)
firstNode.Data = firstNode.Next.Data;
count--;
}
}
}
//And here is my Program
class Program
{
static void Main(string[] args)
{
List listOne = new List();
List listTwo = new List();
listOne.Add(1);
listOne.Add(2);
listTwo.Add(3);
listTwo.Print();
Console.WriteLine("");
listOne.Merge(listOne, listTwo);
Console.WriteLine("");
listOne.Print();
//This line below shows that the data "3" from listTwo is being added to listOne in the list Merge Method
//Console.WriteLine(listOne.firstNode.Next.Next.Data);
Console.ReadKey();
}
}
}

Actual problem in your print method
public void Print()
{
Node node = firstNode;
for (int i = 0; i < this.count; i++)
{
Console.Write(node.Data + "->");
if (node.Next != null)
node = node.Next;
}
}
Alex Sikilinda , you are right the merge method is incomplete.
public object Merge(List a, List b)
{
Node bNode = b.firstNode;
while (bNode != null)
{
a.Add(bNode.Data);
bNode = bNode.Next;
}
return a;
}

I would write it this way:
public void Merge(List b)
{
Node lastNode = GetLastNode();
if (lastNode != null)
{
lastNode.Next = b.firstNode;
}
else
{
this.firstNode = b.firstNode;
}
}
// this method is used to find the last node in current list
private Node GetLastNode()
{
if (this.firstNode == null)
{
return null;
}
Node current = this.firstNode;
while (current.Next != null)
{
current = current.Next;
}
return current;
}
First of all, I changed signature of Merge from public object Merge(List a, List b) to public void Merge(List b). Now we can use it like this:
listOne.Merge(listTwo);
This will link listOne's last element with the first element of listTwo and thus they are merged.
Now we need to change Print method since current version modifies the list, which shouldn't happen:
public void Print()
{
Node currentNode = this.firstNode;
while(currentNode != null)
{
Console.Write(currentNode.Data + ' ');
currentNode = currentNode.Next;
}
}

Instead of assigning the data back to first node I assign the
firstNode = firstNode.Next;
Please check the below Print Code
public void Print()
{
while (this.count > 0)
{
Console.Write(firstNode.Data + "->");
if (firstNode.Next != null)
firstNode = firstNode.Next;
count--;
}
}

List as local and global variable and changing global list value after method call

public Class Card
{
}
public partial class Form
{
List<Card> list2 = new List<Card>();
}
public List<Card> insertInList(ref List<Card> list1)
{
foreach(...)
{
list1.Add(instanceOfObject Card)
}
return list2;
}
private void btn_click(...)
{
insertInList(ref list2);
}
Edit 1 As this is my second edit, I would appreciate If somebody can tell me that I am using "ref" modifiers well in order to have list full of elements after calling insertInList() method?
Edit 2 How would You change this example, but to have same list full of elements after insert method call, but If your list is defined in method insertInList?
Edit3 (The Biggest Issue) I have still problem, that I am getting 3 lists (same names as Namespace.Class) in ListBox while I am expecting only 1?
public List<Karta> ubaciUListu(ref List<Karta> Lista1)
{
//List<Karta> Lista11 = new List<Karta>();
foreach (DataGridViewRow row in dataGridView1.Rows)
{
Karta k = new Karta(0,"","");
// k.Id =(int)row.Cells[0].Value;
k.Pojam =(string) row.Cells[1].Value;
k.Opis = (string)row.Cells[2].Value;
Lista1.Add(k);
}
return Lista1;
}
public partial class Form2 : Form
{
List<Karta> nova = new List<Karta>();
public Form2(List<Karta> input)
{
InitializeComponent();
nova = input;
if (nova.Count!=0)
{
lstBox.DataSource = nova;
}
}

Remove duplicate rows mvc

I have this method
Meeting is a class
Attendees is an ICollection in Meeting
Class
public partial class Meeting
{
public Meeting()
{
this.Attendees = new List<Attendees>();
}
public virtual ICollection<Attendees> Attendees{ get; set; }
[...]
Method Controller
private void RemoveRowsDuplicated(Meeting model)
{
if (model.Attendees != null)
{
foreach (var item in model.Attendees.GroupBy(x => x.UserName).Select(y => y.Last()))
{
context.Attendees.Remove(item);
}
}
}
The objective is remove duplicate Attendees with the same username in the table.
But the current method it deletes all records and keeps the duplicate
Where am I going wrong?

Correct version of your method will look like this:
private static void RemoveRowsDuplicated(Meeting model)
{
if (model.Attendees != null)
{
var duplicates = new List<Attendees>();
foreach (var item in model.Attendees.GroupBy(x => x.UserName).Where(x=>x.Count()>1))
{
duplicates.AddRange(item.Skip(1));
}
duplicates.ForEach(x=>context.Attendees.Remove(x));
}
}

You can try writing raw SQL and invoking via EF and return Attendees objects in a list.
var query = "Select * from Attendees group by username";
var attendeesList = dbContext.Database.SqlQuery<Attendees>(query).ToList<Attendees>();

As I can see you grouped elements by name and remove last item. So you remove unique elements.
Like this
private void RemoveRowsDuplicated(Meeting model)
{
if (model.Attendees != null)
{
var temporaryAtendees = new List<Attendees>();
foreach(var item in model.Attendees)
{
if (temporaryAtendees.Contains(item))
{
context.Attendees.Remove(item);
}
else
{
temporaryAtendees.Add(item);
}
}
}
}

c# insert item in order custom linked list

im trying to add the number 8 into my list using the InsertInOrder method
e.g. my current list 5, 10, 12, 14, 26, 45, 52
after inserting new node 5, 8, 10, 12, 14, 26, 45, 52
i know i have to iterate through the list in order to find the correct position for it
but where do i start?
class LinkList
{
private Link list = null; //default value – empty list
public void AddItem(int item) //add item to front of list
{
list = new Link(item, list);
}
public void InsertInOrder(int item)
{
Link temp = list;
while (temp != null)
{
AddItem(item);
Console.WriteLine(temp.Data);
temp = temp.Next;
}
}
public void DisplayItems() // Displays items in list
{
Link temp = list;
while (temp != null)
{
Console.WriteLine(temp.Data);
temp = temp.Next;
}
}
Link class:
class Link
{
private int data;
private Link next;
public Link(int item) //constructor with an item
{
data = item;
next = null;
}
public Link(int item, Link list) //constructor with item and list
{
data = item;
next = list;
}
public int Data //property for data
{
set { this.data = value; }
get { return this.data; }
}
public Link Next //property for next
{
set { this.next = value; }
get { return this.next; }
}
}
}

Your code looks pretty clean. I'm not going to post a full solution for you but I will give you a skeleton out line of how you could implement InsertInOrder. Note that there are many ways to do this. All you have to do is fill in the if conditions.
public void InsertInOrder(int item)
{
Link temp = list;
// check to see if the item goes at the front of the list...
// hint : there are 2 conditions where it needs to go in the front.
if (********* || **********)
{
list = new Link(item, list);
}
else
{
while (temp != null)
{
// you have to look at the next item and see if it's bigger
// which means it goes next.
// if there isn't a next item this item belongs next.
if (*********** || // there is no next item
***********) // this item is bigger than the next item
{
temp.Next = new Link(item, temp.Next);
// we are done so set temp to null so we exit the loop
temp = null;
}
else
{
// move on to the next item
temp = temp.Next;
}
}
}
}