Yesterday I wrote a piece of code to remove all the controls in a form that fulfills certain criteria. Writing it naively, this is what I come up with.
for (int i = 0; i < this.Controls.Count; ++i)
{
if (this.Controls[i].Name.Length == 2)
{
this.Controls.Remove(this.Controls[i);
}
}
But it so happens that the code is wrong. I then change it to:
foreach (Control ctr in this.pbBoardImage.Controls)
{
if (ctr.Length == 2)
{
this.Controls.Remove(ctr);
}
}
But it still wasn't correct.
I know that the correct way would be:
for (int i = this.Controls.Count - 1; i >= 0; i--)
{
if (this.Controls[i].Name.Length == 2)
{
this.Controls.Remove(this.Controls[i]);
}
}
However it still doesn't feel elegant. I couldn't use List.RemoveAll, since this.Controls wasn't a List. So can I ask for a more elegant way, preferably without using a loop?
Not sure why you didn't like this answer... I've highlighted the important RemoveAt; however, as an alternative in .NET 3.5/C# 3.0: LINQ:
var qry = from Control control in Controls
where control.Name.Length == 2
select control;
foreach(var control in qry.ToList()) {
Controls.Remove(control);
}
(original)
You can't Remove within foreach - it breaks the iterator. A common approach here is to iterate backwards:
for (int i = this.Controls.Count - 1; i >= 0; i--) {
if (this.Controls[i].Name.Length == 2) {
this.Controls.RemoveAt(i); // <=========== *** RemoveAt
}
}
This avoids the "off by one" issues, etc.
Related
I have this loop and multiple leds. The names of the leds are Led0, Led1, Led2 etc
Now i want to change the background of each Led with this loop so i use the counter iTeller.
I use WPF and only work in the mainwindow.
for (int iTeller = 0; iTeller < bits.Count(); iTeller++)
{
if (bits[iTeller] == 1)
{
//this doesn't work
*Led+iTeller+.Background = Brushes.Green;*
}
}
Try Like This (WPF)
for (int iTeller = 0; iTeller < bits.Count(); iTeller++)
{
if (bits[iTeller] == 1)
{
object i = this.FindName("Led" & iTeller);
if (i is CheckBox)
{
CheckBox k = (CheckBox)i;
MessageBox.Show(k.Name);
}
}
}
This will not work for a lot of reasons. The first is, that your leds are some type of control, which you need in a variable, you cannot simply call them like this.
Do you use WPF or Winforms?
You need a list of your leds, then you can iterate over the list and assign the value to each led
You cannot resolve a variable name like this, you can use the Find method (at least in Windows Forms), to find a named control.
You can also store the controls in an array, that way you prevent using relatively slow Find calls and other error checking:
var leds = new CheckBox[] { Led0, Led1, Led2, Led3, Led4, Led5, Led6, Led7 };
for (int iTeller = 0; iTeller < bits.Count(); iTeller++)
{
if (bits[iTeller] == 1)
{
leds[iTeller].Background = Brushes.Green;
}
}
This worked
for (int iTeller = 0; iTeller < bits.Count(); iTeller++)
{
if (bits[iTeller] == 1)
{
var myCheckbox = (CheckBox)this.FindName("Led" + iTeller);
myCheckbox.Background = Brushes.Green;
}
}
Thanks everyone
For homework assignment we have to program a Intersection merge of 2 ArrayLists. I have done it using the following code
public void Intersection()
{
foreach (object obj1 in Developed)
{
Apps xApp = (Apps)obj1;
foreach (object obj2 in DPloyed)
{
Apps yApp = (Apps)obj2;
if (xApp.CompareName(yApp) == 0)
{
Inter.Add(yApp);
}
}
}
}
I would like to implement it rather using the while loop but the following code seems to keep missing elements in the list. It puts the first elements in the new intersection list but once the length of developed is increased from 1 element to 5 elements or more it does not add the new elements.
public void Intersection()
{
int i = 0;
int j = 0;
while (i < Developed.Count && j < DPloyed.Count)
{
Apps curA = (Apps)Developed[i];
Apps curB = (Apps)DPloyed[j];
if (curA.CompareName(curB) == 0)
{
Inter.Add(curA);
i++;
j++;
}
else if (curA.CompareName(curB) < 0)
{
i++;
}
else
j++;
}
}
Any help as to why the while loop does not work would be appreciated.
Thanks
Do this
while (i < Developed.Count || j < DPloyed.Count)
because may be both list may be having different Count.
and you need to put extra checks inside loop for indexes so that you don't get Index out of Range Exception.
Problem was not in the actual code for the merges. Problem found in my compare methods.
So, I have a listbox with x number of items. On top of the listbox I have a TextBox (this is the search field). I try do develop an algorithm that removes items from the listbox, if it doesn't contain the searchword (variable keyword in the code). This is supposed to happen for each key the user types (on-the-fly). So, the code:
private void _keywordTextBox_TextChanged(object sender, EventArgs e)
{
string keyword = _keywordTextBox.Text;
if (keyword == searchtext || isSpace) // do nothing if space is typed - searchtext is a templatetext in the textbox ("type here to search...")
return; // ignore
else if (keyword == "")
{
listBox.Items.Clear();
foreach (string s in originalList)
listBox.Items.Add(s);
}
else
{
List<string> selection = new List<string>();
foreach (string s in originalList) // originalList is the listbox at startup
selection.Add(s);
listBox.BeginUpdate();
string[] keywordSplit = keyword.Split(' ');
try
{
for (int i = originalList.Count - 1; i >= 0; i--)
{
string[] selectionSplit = selection[i].Split(' ');
int l = 0; // number of hits
for (int j = 0; j < selectionSplit.Length; j++)
{
for (int k = 0; k < keywordSplit.Length; k++)
{
if (selectionSplit[j].ToLower().Contains(keywordSplit[k].ToLower()))
{
l++;
break;
}
}
}
if (l < keywordSplit.Length) // Not hit on all keywords
selection.RemoveAt(i);
}
}
finally
{
listBox.Items.Clear();
foreach (string s in selection) // Add selection in listbox
listBox.Items.Add(s);
if (listBox.Items.Count > 0)
listBox.SetSelected(0, true); // Select first item in listbox
listBox.EndUpdate();
}
}
}
The problem is hard to describe, other than it doesn't work as intended. The behavour is, as far as I can see, sporadic.
If I search for "ck flow", I should get a hit for stackoverflow. More importantly, it should also work if I deletes chars (delete key of backspace). Anybody?
Edit: more details:
The listbox should shrink and grow on each keystroke, based on what the user searches for. The listbox should keep every item that matches the keyword typed in by the user, and filter away that doesn't match.
Or you could try to work out a Regular Expression:
private void textBox1_TextChanged(object sender, EventArgs e)
{
string keyword = textBox1.Text;
if (string.IsNullOrEmpty(keyword.Trim()))
{
listBox1.Items.Clear();
listBox1.Items.AddRange(_originalList.ToArray());
}
else
{
Regex regex = new Regex(GetRegexPatternFromKeyword(keyword));
List<string> selection =
_originalList.Where(s => regex.IsMatch(s)).ToList();
listBox1.Items.Clear();
listBox1.Items.AddRange(selection.ToArray());
}
}
private static string GetRegexPatternFromKeyword(string keyword)
{
string[] words =
keyword.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries).Select(word => "(?=.*" + word.Replace(")", #"\)") + ")").ToArray();
return string.Join("", words);
}
disclaimer: there could be some cases where an input would 'destroy' the regex pattern
Your code increases l too often. For instance;
the text 'aaa aaa aaa' with searchword 'aaa bbb' will give an l of 3 because every time you find 'aaa' you increase l. So this will be a match even though 'bbb' is never found.
You can fix this (among others) by deleting found parts of keywordsplit and recreating keywordsplit anew before every search of a new selectionline.
l++;
break;
becomes
l++
keywordSplit.RemoveAt[k];
break;
and move
string[] keywordSplit = keyword.Split(' ');
to just before you start the k loop
Altough I feel there might be better ways to achieve what you want with a bit cleaner and faster code it should work.
I got it to work. #IvoTops helped me in the right direction. Just loop trough all the keyword first, and then the selections.
for (int j = 0; j < keywordSplit.Length; j++)
{
for (int k = 0; k < selectionSplit.Length; k++)
{
if (selectionSplit[k].ToLower().Contains(keywordSplit[j].ToLower()))
{
l++;
break;
}
}
}
Seems to work ok now.
i have lot of pictureboxes named this way: PBr1_1, PBr1_2, ... PBr1_9
I'd like to make loop
for (int i = 0; i < 10; i++)
{
if (Textbox.Text[i].ToString() == "1"){ "PBr1_"+"i".Tag = "cb.png";}
}
so for i=0 => PBr1_0, i=10 => Pbr1_10.
Example i have value in textbox: 0001011101 - then if value in textbox is "1" then i'd like to change picturebox tag.
How to automate this process, using for example loop "for"?
I suppose your controls are on a WinForm (this) and the ones with that name are all pictureboxes.
If so, that's the way ----
for (int i = 0; i < 10; i++)
{
if (Textbox.Text[i].ToString() == "1")
{
Control[] c = this.Controls.Find("PBr1_" + i.ToString(), true);
if(c != null && c.Length > 0) c[0].Tag = "cb.png";
}
}
You can put the picture boxes in to a List<PicutreBox> and iterate over the list.
var pictures = new List<PictureBox>();
pictures.Add(pic1);
pictures.Add(pic2);
//...
for (int i = 0; i < 10; i++)
{
if (Textbox.Text[i].ToString() == "1")
pictures[i].Tag = "cb.png";
}
Dynamic variable names as in your example are not supported.
Create an array (or list) that contain the picture boxes and use those within the for loop.
You can also use reflection but in my opinion it is best not to use that in this case.
If you are using WinForm you can use Control.Find method to locate a control by name
Once you have got the control you can easily change any property
I want to remove whole ListviewItems in my Listview except first Column. I have got a method but it sometimes throw ArgumentRangeException that i could not find why.
private void ListViewClear()
{
for (int i = 0; i < lstKullanicilar.Items.Count; i++)
{
if (lstKullanicilar.Items[i].SubItems.Count != 1)
{
lstKullanicilar.Items[i].SubItems.RemoveAt(1);
lstKullanicilar.Items[i].SubItems.RemoveAt(2);
lstKullanicilar.Items[i].SubItems.RemoveAt(3);
lstKullanicilar.Items[i].SubItems.RemoveAt(1);
lstKullanicilar.Items[i].SubItems.RemoveAt(1);
}
}
Try somethin like this:
for (int i = 0; i < lstKullanicilar.Items.Count; i++) {
while(lstKullanicilar.Items[i].Count > 1){
lstKullanicilar.Items[i].SubItems.RemoveAt(1);
}
}
The problem with your code is probably that you have a variable amount of items in the SubItems-collection. WIth the code you showed, you must at least have 6 items in the subitems-collection, for not getting an arugment exception.