My current code:
Remove()
{
for (int i = 0; i < ConGridView.RowCount; i++)
{
if (ConGridView.Rows[i].Cells[0].Value.ToString() == Address)
{
ConGridView.Rows.RemoveAt(i);
break;
}
}
}
So what I am trying to call the remove function every time a client disconnect. the function will remove the connection address from the datagridview. It works well when clients are disconnection one by one. However, if 100 connections gets dropped and it tries to remove 100 connections in less than a second, than it errors out saying "Row Index provided is out of range". How should I check for that ?
So far I've tried:
Try, catch.
if (ConGridView.Rows[i] != null), if (i < ConGridView.RowCount)
None of it seem to work so far. I've also got results using (i < ConGridView.RowCount) where i is 26 while RowCount is 24, but the remove at function still activates..
Any idea on this ?
You can't do this. Your code loops through all the rows in ConGridView, but it deletes them as you do. Therefore, at some point you will try to access an item you have deleted, which will cause the error you described.
Probably the best approach it to iterate through the rows in reverse order. This way, deleting a row at the end won't affect when you access rows at the start.
The problem is you initialise your for loop with the current count of rows and then start removing those same rows from the datagridview. At some point your for loop will try to remove a row at an index that is greater than the number of rows left.
Try this instead:
for (int i = ConGridView.RowCount - 1; i >= 0; i--)
{
if (ConGridView.Rows[i].Cells[0].Value.ToString() == Address)
{
ConGridView.Rows.RemoveAt(i);
break;
}
}
why dont you get the total count to a separate variable and then iterate
Remove()
{
int totalConnections = ConGridView.RowCount;
for (int i = 0; i < totalConnections ; i++)
{
if (ConGridView.Rows[i].Cells[0].Value.ToString() == Address)
{
ConGridView.Rows.RemoveAt(i);
break;
}
}
}
This issue is becuase you are modifying the collection your are iterating over. It will be better if you use a temporary array and two loops to remove your entries.
Remove()
// You can use an array/list or whatever you want below.
Collection<DataGridViewRow> rowsToDelete = new Collection<DataGridViewRow>();
for (int i = 0; i < ConGridView.RowCount; i++)
{
if (ConGridView.Rows[i].Cells[0].Value.ToString() == Address)
{
rowsToDelete.Add(ConGridView.Rows[i]);
break;
}
}
// now remove the marked entries.
foreach(DataGridViewRow deletedRow in rowsToDelete)
{
ConGridView.Rows.Remove(deletedRow);
}
When you remove an item from an array, it is reconstructed; shifting the remaining elements up by one to remove the gap of the index you have removed.
1. guybrush threepwood
2. murray
3. elaine
4. Jimmy Gibbs Jr.
If you remove 2. item in here; it becomes this:
1. guybrush threepwood
2. elaine
3. Jimmy Gibbs Jr.
When you are iterating, imagine:
for (int i = 0; i < myArray.Count; i++)
{
if (i == 2) myArray.RemoveAt(i);
}
While running this, when i = 3, the element at 3 has changed, you expect it to be 'elaine' but it is 'Jimmy Gibbs Jr.'. One way to fix this is decrease i by one if we delete it, making sure that i refers to correct value.
for (int i = 0; i < myArray.Count; i++)
{
if (i == 2)
{
myArray.RemoveAt(i);
i--;
}
}
I would go for LINQ in this case, though, everything is easier with that.
myArray.RemoveAll(x => x == "murray");
I've tried all the suggestions posted by everyone here, however, the error was still there.
I've solved the problem using a different way... I've switched to TreeNodeView since that's what I was going to use ultimately. Now I can remove as many connection as i want with:
For each(TreeNode TN in ConTreeView)
{
ConTreeView.Nodes.Remove(TN);
}
Related
I want to check if a DateTime in CustomFormat is greater than another DateTime, but the checking is okay after that the code removes a lot of item and none of that correct. Here is my code. The job is to remove any ListViewItem which is older than 3 days.
for (int i = 0; i < lvValid.Items.Count; i++)
{
if (DateTime.Now.AddDays(-3) > DateTime.Parse(lvValid.Items[i].SubItems[1].Text))
{
lvValid.Items[i].Remove();
}
}
I've already tried foreach but it didn't help. And its removing every second element, but its not correct
One big problem with a forward loop is that if you remove one item, then the indices of the remaining will shift leftwards. So at i == 1 the next item will be at 1 after the removal. Then i will be incremented and skip the former next item.
I would suggest to use a backward loop:
for (int i = lvValid.Items.Count - 1; i >= 0 ; i--)
{
if (DateTime.Now.AddDays(-3) > DateTime.Parse(lvValid.Items[i].SubItems[1].Text))
{
lvValid.Items[i].Remove();
}
}
personally I would advice to work with the original data. First filter the data according to your condition and then repopulate the ListView.
Maybe you should Reverse for loop & not use .AddDays(-3)
for (int i = lvValid.Items.Count - 1; i >= 0; i--)
{
if (DateTime.Now <= DateTime.Parse(lvValid.Items[i].SubItems[1].Text).AddDays(3);
{
lvValid.Items[i].Remove();
}
}
If you want to use forward loop (if order of removing matters) you should increment i++ when you don't remove an item:
// we don't want redrawing on each removing (i.e. lvValid blicking)
lvValid.BeginUpdate();
try
{
for (int i = 0; i < lvValid.Items.Count; ) // don't icrement i here...
if (DateTime.Now.AddDays(-3) > DateTime.Parse(lvValid.Items[i].SubItems[1].Text))
lvValid.Items[i].Remove();
else
++i; // ... but there
}
finally
{
// when finisihing removing, redraw lvValid if required
lvValid.EndUpdate();
}
I have bound the data to ListView from multiple sources. And there is duplicate data, I want to remove all the duplicates from that ListView. I used the following code but it is not helping.
listview.Sorting = System.Windows.Forms.SortOrder.Ascending;
for (int i = 0; i < listview.Items.Count - 1; i++)
{
if (listview.Items[i].Tag == listview.Items[i + 1].Tag)
{
listview.Items[i + 1].Remove();
}
}
Without a good, minimal, complete code example, it's not possible to know for sure what the problem is. However, most likely your Tag values are reference types and not actually identical object instances.
Assuming the objects override the Equals() method, you can fix it by using that method instead:
listview.Sorting = System.Windows.Forms.SortOrder.Ascending;
for (int i = 0; i < listview.Items.Count - 1; i++)
{
if (listview.Items[i].Tag.Equals(listview.Items[i + 1].Tag))
{
listview.Items[i + 1].Remove();
i--;
}
}
Note that you also had a bug in which you would skip checking elements if there were three or more duplicates of a given value. You can fix this by decrementing i when you remove an element (see above).
Hi I have a problem with a for loop.
It looks like this
for (int i = 0; i < ObjectManager.Instance.Objects.Count; i++)
{
if (ObjectManager.Instance.Objects[i] is Asteroid)
{
ObjectManager.Instance.Objects.Remove(ObjectManager.Instance.Objects[i]);
}
}
But the count gets shorter while I remove objects, which causes the loop to end prematurely. Is there a way to do this without a bunch of extra loops.
Why don't you loop backward?
// Just change the order from Count - 1 down to 0
for (int i = ObjectManager.Instance.Objects.Count - 1; i >= 0; --i)
{
if (ObjectManager.Instance.Objects[i] is Asteroid)
{
ObjectManager.Instance.Objects.Remove(ObjectManager.Instance.Objects[i]);
}
}
In case you have to loop forward (e.g. if Instances should be deleted in the order they are created because they are depend on each other) you can modify for loop in this way:
for (int i = 0; i < ObjectManager.Instance.Objects.Count;) // <- No increment here
if (ObjectManager.Instance.Objects[i] is Asteroid)
ObjectManager.Instance.Objects.Remove(ObjectManager.Instance.Objects[i]);
else
i += 1; // <- Increment should be here!
Yet another possibility is Linq:
ObjectManager.Instance.Objects.RemoveAll(item => item is Asteroid);
Three options:
If ObjectManager.Instance.Objects is a List<T>, use List<T>.RemoveAll with a predicate, making your code much simpler:
// This replaces your whole loop...
ObjectManager.Instance.Objects.RemoveAll(x => x is Asteroid);
Count from the end of the collection rather than from the start, so that you don't need to adjust the index afterwards:
for (int i = ObjectManager.Instance.Objects.Count - 1; i >= 0; i--)
Just decrement i after calling Remove, so that you'll look at the right index on the next iteration.
Note that in the second and third options your code will be a lot simpler to read if you extract the expression ObjectManager.Instance.Objects into a local variable before you use it 4 times. Also consider using RemoveAt(i) rather than Remove(instances[i]), assuming RemoveAt is available for the type you're using.
I'm trying to see if when a user enters some text it searches the array for any matches, and whatever doesn't match gets removed from the array;
string search = textBox1.Text;
for (int i = 0; i < staffUsers.Count; i++)
{
if (!(staffUsers[i].staff_name.Contains(search)))
{
staffUsers.Remove(staffUsers[i]);
}
}
I have some rubbish names in my array 'Rob Dob','Joe Bloggs', 'h h', 'ghg hgh', and if the search variable ended up being 'R', Joe Bloggs would get removed but 'h h' and 'ghg hgh' stay there, but there is no R involved there at all? any reason why>?!
You have to iterate backwards in order to remove from an array. Every time you remove an item, your array gets smaller. By going backwards, that fact does not matter.
string search = textBox1.Text;
for (int i = staffUsers.Count - 1; i >= 0 ; i--)
{
if (!(staffUsers[i].staff_name.Contains(search)))
{
staffUsers.Remove(staffUsers[i]);
}
}
The problem with your code is that you are removing items as you iterate over it. You remove an item, but keep iterating, even though the size of the array changes when you remove an item.
You need to reset your i value after you remove something. Alternatively, you need to use a built in to do the heavy lifting:
staffUsers.RemoveAll(i => !(i.staff_name.Contains(search)));
Uses a tiny LINQ expression to do the work. Remove all items where that predicate matches. i represents an item to apply the expression to. If that expression evaluates to true, away it goes.
Long story short, whenever you remove an item at index [i], you skip the item at index [i+1]. For example, if your array looks like:
{'Joe Bloggs', 'Rob Dobb', 'h h', 'gafddf'}; i=0
remove Joe Bloggs, which is at position 0.
{Rob Dobb', 'h h', 'gafddf'}; i=1
remove 'h h', which is at position 1
{Rob Dobb', 'gafddf'}; i=2
i is not less than yourArray.Count, so the loop stops. There is no position 2.
The quickest fix is to add i-- if you remove something from index [i]. In your case,
staffUsers.Remove(staffUsers[i]);
i--;
Hope this helps!
In each iteration of the loop, either remove an item or increment the counter, not both operations. Otherwise, you'll skip the next array element whenever you remove an array element:
string search = textBox1.Text;
for (int i = 0; i < staffUsers.Count;)
{
if (!(staffUsers[i].staff_name.Contains(search)))
{
staffUsers.Remove(staffUsers[i]);
}
else
{
i++;
}
}
The simplest way to solve the above problem is using LINQ.
Following code disentangle above problem.
string search = textBox1.Text;
staffUsers= (from user in staffUsers
where !user.Contains(search)
select user).ToArray<string>();
Note: I assumed staffUsers is array of string.
string search = textBox1.Text;
for (int i = 0; i < staffUsers.Count; i++)
{
if (!(staffUsers[i].staff_name.Contains(search)))
{
staffUsers.Remove(staffUsers[i]);
// reset the index one stepback
i--;
}
}
Why doesn't the code below clear all array list data?
Console.WriteLine("Before cleaning:" + Convert.ToString(ID.Count));
//ID.Count = 20
for (int i = 0; i < ID.Count; i++)
{
ID.RemoveAt(i);
}
Console.WriteLine("After cleaning:" + Convert.ToString(ID.Count));
//ID.Count = 10
Why is 10 printed to the screen?
Maybe there is another special function, which deletes everything?
You're only actually calling RemoveAt 10 times. When i reaches 10, ID.Count will be 10 as well. You could fix this by doing:
int count = ID.Count;
for (int i = 0; i < originalCount; i++)
{
ID.RemoveAt(0);
}
This is an O(n2) operation though, as removing an entry from the start of the list involves copying everything else.
More efficiently (O(n)):
int count = ID.Count;
for (int i = 0; i < originalCount; i++)
{
ID.RemoveAt(ID.Count - 1);
}
or equivalent but simpler:
while (ID.Count > 0)
{
ID.RemoveAt(ID.Count - 1);
}
But using ID.Clear() is probably more efficient than all of these, even though it is also O(n).
`Array.Clear()`
removes all items in the array.
`Array.RemoveAt(i)`
removes the element of ith index in the array.
ArrayList.Clear Method
Removes all elements from the ArrayList.
for more detail : http://msdn.microsoft.com/en-us/library/system.collections.arraylist.clear.aspx
After removing 10 items, ID.Count() == 10 and i == 10 so the loop stops.
Use ID.Clear() to remove all items in the array list.
Use the clear() Method
or
change ID.RemoveAt(i); to ID.RemoveAt(0);
Whenever an element is removed from the collection, its index also changes. Hence when you say ID.RemoveAt(0); the element at index 1 now will be moved to index 0. So again you've to remove the same element (like dequeuing). until you reach the last element. However if you want to remove all the elements at once you can better use the Clear() method.
Your code does:
ID.RemoveAt(0);
...
ID.RemoveAt(9);
ID.RemoveAt(10); \\ at this point you have already removed 10
\\ items so there is nothing left on 10- 19, but you are left with
\\ the 'first' 10 elements
...
ID.RemoveAt(19);
Generally speaking your method removes every second element from the list..
Use ArrayList.Clear instead as other have mentioned.