I tried many times to resolve this case but I always get an error because it's an Image in an ImageList. What code do I need to literally re-add the removed Image from the list. This is my code (The final line doesn't work).
int index9 = random.Next(0, normalCards1.Count - 1);
pictureBox9.Image = normalCards1[index9];
normalCards1.RemoveAt(index9);
...
normalCards1.Insert(index9);
you need to pass T item as well with index.
you can add it back this way:
normalCards1.Insert(index9,pictureBox9.Image);
See List.Insert Method MSDN docs here
ImageListCollection which is the type of ImageList.Images does not provide a way to insert items by index.
If you want to shuffle or somehow else reorder images you need to remove them all and add them again after reordering. I.e. adding all images to a List<T>, sort, and use AddRange.
You can also try using indexed access (imageList.Images[3] = ... ) to swap items.
Related
Say I have an ObservableCollection with two items:
0: dateUnix: 333
1: dateUnix: 222
Now I want to add a new Item:
dateUnix: 300
If I just were to use the .add() method, the item would get added at the end. But I want the item to be inserted between 222 and 300 since this would make the list sorted.
How do I insert an item at a certain position where it is less then item value after and higher then item value before?
Of the top, I can think of two ways of doing this.
One would be, as was pointed out in the comments, to just insert and sort afterwards.
Another, more complex and more rewarding way would be to find the index of the first item greater or lesser than the one you're inserting and insert it at that index. Your list seems to be sorted in descending order, so it'd need to be the first lesser than.
You could achieve this using LINQ:
ObservableCollection<Int> collection = new ObservableCollection(new List<int>{333,222}); // == [333,222]
Int toInsert = 300;
collection.Insert(collection.IndexOf(collection.First(elem => elem < toInsert)), toInsert); // output == [333,300,222]
See this Fiddle for a working example.
If your collection is already sorted, just find the appropriate index to insert the element at (either via a linear or the faster binary search) and use Insert to store the element at that specific index.
How do I remove the last two rows from a List.
At present, I am removing the 2 rows manually as shown below. However, there might be an instance where I have to define the number of rows to be removed as n. So, it will remove n number of rows from the bottom of the list. How can I make this change?
rows.RemoveAt(rows.Count - 1);
rows.RemoveAt(rows.Count - 2);
You could use RemoveRange:
rows.RemoveRange(rows.Count - n, n);
You could use LINQ:
rows = rows.Take(rows.Count - n).ToList();
As Spender said, there is a potential issue in your code. I call this a "Index Race Condition". After you remove the last element, something else becomes the new last Element. It is something you have to look out for with Indexed Collections. Keyd collections do not suffer from it.
In addition to what others said regarding using "RemoveRange" (if availible) or LINQ, there is also a chance you got the wrong collection type.
The Queue[T] and the Stack[T] are specialized collections for first-in, first-out and first-in, last-out cases respectively.
I would like to create a list variable of items from another list. So lets say I have a list of 100 items I would like to pull items 25 - 35 and put them inside of another list. is there a way of doing this without calling a big for statement and pulling out the element one by one and putting that into a list.
you can use .Skip and .Take from System.Linq ....
Like this:
var result = myList.Skip(24).Take(10);
and if you need use ToList on the result to get another list
For a List<T>, you can use the GetRange Method.
Creates a shallow copy of a range of elements in the source List(Of
T).
Do note that the second argument represents the count of elements in the range, not the end-index of the range.
Since you mention ArrayList, I should point out that while it too has a GetRange, method, the type is considered essentially legacy since .NET 2.0.
Use both Take and Skip
var newList = oldList.Skip(25).Take(10);
Anyone know how to select a certain amount of items in a List to bind to a DataSource? Basically I'm getting back 10 items (which I don't have control over) and I only need to show 5. Originally I was thinking of using a loop and adding 5 items to a new list but that seems like a lot of code. Is there an expression that I can use to select the first 5?
//Returns a List<DataItem>
MyDataListControl.DataSource = Helper.GetDataItems(); //<= Possible expression?
You may take a look at the Skip and Take LINQ extension methods. So in your case if you wanted to take only the first 5 elements of some IEnumerable<T>:
MyDataListControl.DataSource = Helper.GetDataItems().Take(5).ToList();
What about List's GetRange method? Have you tried that? I don't the internal workings of the method; whether it also creates a new list or not.
GetRange(int index, int count)
Here is the msdn link for it.
RemoveRange will probably be best as you won't have to instanciate a new list, unless that happens internally anyway.. Just make sure you're always getting 10 items or you'll potentially get an ArgumentOutOfRangeException.
list.RemoveRange(5, 5);
That should leave you with the first five items.
Greetings!
I am using List class.I will define my code below.
List<c1> lis = new List<c1>();
where c1 is class.
I want to find index of particular item in List.say in list i have, 10,20,30,40 inside List.In this how i find the index of 30.Please help me to get a solution.
Thank You
Regards
Jennie
Maybe this is what are you looking for? List.IndexOf Method (T)
Use:
lis.IndexOf(value)
That should return the first index of the requested value.
c1 c = new c1(); should be INSIDE the loop.
Actualy, what is your code supposed to represent? Are you aware you have Array inside a list. So in your case, you end up with List with 4 items of same instance of single object, that has array of 4 items with strings "0","1","2","3". You should fix this first before you ask your question again.