C removing items from listbox

Question

I have a listbox being populated from a SQLDATA pull  and it pulls down some columns that i dont want like OBJECT dfj  OBJECT daskd   The key is all of these being with OBJECT   is there a way to remove these from the listbox   I cannot change my SQL statement   i tried this    foreach  string item in listBox1 Items          string removelistitem    OBJECT        if item Contains removelistitem                   listBox1 Items Remove item               but it gave me the error        List that this enumerator is bound to has been modified  An enumerator can only be used if the list does not change

User · Answer

You can do it in 1 line  by using Linq  listBox1 Cast lt ListItem gt    Where p  gt p Text Contains  OBJECT    ToList   ForEach listBox1 Items Remove

User · Answer

You could try this method   List lt string gt  temp   new List lt string gt          foreach  string item in listBox1 Items                string removelistitem    OBJECT           if item Contains removelistitem                         temp Items Add item                          foreach string item in temp               listBox1 Items Remove item           This should be correct as it simply copies the contents to a temporary list which is then used to delete it from the ListBox   Everyone else please feel free to mention corrections as i m not 100  sure it s completely correct  i used it a long time ago

User · Answer

The error you are getting means that   foreach  string item in listBox1 Items    should be replaced with  for int i   0  i  lt  listBox1 Items Count  i          string item    string listBox1 Items i     In other words  don t use a foreach   EDIT  Added cast to string in code above  EDIT2  Since you are using RemoveAt    remember that your index for the next iteration  variable i in the example above  should not increment  since you just deleted it

User · Answer

You can use following code too    foreach  var item in listBox1 Items Cast lt string gt    ToList            string removelistitem    OBJECT        if  item Contains removelistitem                  listBox1 Items Remove item

User · Answer

You can t modify the references in an enumerator whilst you enumerate over it  you must keep track of the ones to remove then remove them   This is an example of the work around   List lt string gt  listbox   new List lt string gt     List lt object gt  toRemove   new List lt object gt      foreach  string item in listbox        string removelistitem    OBJECT       if  item Contains removelistitem                 toRemove Add item            foreach  string item in toRemove        listbox Remove item       But if you re using c 3 5  you could say something like this   listbox Items   listbox Items Select n   gt   n Contains  OBJECT

User · Answer

I found out the hard way that if your listbox items are assigned via a data source  List lt String gt  workTables   hhsdbutils GetWorkTableNames    listBoxWork DataSource   workTables       you have to unbind that before doing the removal   listBoxWork DataSource   null  for  int i   listBoxWork Items Count - 1  i  gt   0  --i        if  listBoxWork Items i  ToString   Contains listboxVal                 listBoxWork Items RemoveAt i             Without the  listBoxWork DataSource   null   line  I was getting   Value does not fall within the expected range

User · Answer

You can t use an enumerator  you have to loop using an index  starting at the last item   for  int n   listBox1 Items Count - 1  n  gt   0  --n        string removelistitem    OBJECT       if  listBox1 Items n  ToString   Contains removelistitem                 listBox1 Items RemoveAt n

User · Answer

You want to iterate backwards through using a counter instead of foreach   If you iterate forwards you have to adjust the counter as you delete items   for int i listBox1 Items Count - 1  i  gt  -1  i--          if listBox1 Items i  Contains  OBJECT                  listBox1 Items RemoveAt i

User · Answer

for  int i   0  i  lt  listBox1 Items Count  i                  if  textBox1 Text    listBox1 Items i  ToString                          jeElement   true              break                      if  jeElement                label1 Text    je element             else               label1 Text    ni element             textBox1 ResetText        textBox1 Focus        private void Form1 KeyDown object sender  KeyEventArgs e        if  e Alt    true  amp  amp  e KeyCode    Keys A                buttonCheck PerformClick

User · Answer

Sorry guys i had to adjust the string  sqldatapull   dr 0  ToString                    if  sqldatapull StartsWith  OBJECT                                          sqldatapull                                         listBox1 Items Add sqldatapull                   for  int i   listBox1 Items Count - 1  i  gt   0  i--                                        if  String IsNullOrEmpty listBox1 Items i  as String                           listBox1 Items RemoveAt i

User · Answer

protected void lbAddtoDestination Click object sender  EventArgs e                        AddRemoveItemsListBox lstSourceSkills  lstDestinationSkills                     protected void lbRemovefromDestination Click object sender  EventArgs e                        AddRemoveItemsListBox lstDestinationSkills  lstSourceSkills                     private void AddRemoveItemsListBox ListBox source  ListBox destination                        List lt ListItem gt  toBeRemoved   new List lt ListItem gt                 foreach  ListItem item in source Items                                if  item Selected                                        toBeRemoved Add item                       destination Items Add item                                               foreach  ListItem item in toBeRemoved  source Items Remove item

User · Answer

The problem here is that you re changing your enumerator as you remove items from the list  This isn t valid with a  foreach  loop  But just about any other type of loop will be OK   So you could try something like this   for int i 0  i  lt  listBox1 Items Count          string removelistitem    OBJECT       if listBox1 Items i  Contains removelistitem            listBox1 Items Remove item       else           i

User · Answer

You can t modify a collection while you re iterating over it with foreach   You might try using a regular for   statement    You may need to iterate backwards from the end of the collection to make sure you cover every item in the collection and don t accidentally overrun the end of the collection after removing an item  since the length would change    I can t remember if  NET accounts for that possibility or not

User · Answer

Your question implies that you re willing to modify other parts of the code  even though you can t modify the SQL Statement itself  Instead of removing them from the ListBox Collection  it might be easier to just exclude them in the first place   This code assumes you re connecting to SQL Server   void PopulateListBox ListBox listToPopulate        SqlConnection conn   new SqlConnection  myConnectionString         SqlCommand cmd   new SqlCommand  spMyStoredProc   conn       cmd CommandType   CommandType StoredProcedure      SqlDataReader reader   cmd ExecuteReader        while  reader Read                  string item   reader GetString 0     or whatever column is displayed in the list         if   item Contains  OBJECT                 listToPopulate Items Add item              But if you re absolutely determined to do it this way you should check out this question on modifying an enumerable collection while iterating through it

User · Answer

With this code you can remove every item from your listbox     Notice that you should write this code in the click event of your button            if  listBox1 SelectedIndex    -1                        listBox1 Items RemoveAt listBox1 SelectedIndex

User · Answer

You can try this also  if you don t want to deal with the enumerator   object ItemToDelete   null  foreach  object lsbItem in listbox1 Items       if  lsbItem ToString       -ITEM-              ItemToDelete   lsbItem                                            if  ItemToDelete    null      listbox1 Items Remove ItemToDelete

[c#] C# removing items from listbox

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