Deleting specific rows from DataTable

Question

I want to delete some rows from DataTable  but it gives an error like this      Collection was modified  enumeration operation might not execute     I use for deleting this code     foreach DataRow dr in dtPerson Rows       if dr  name   ToString     Joe           dr Delete        So  what is the problem and how to fix it  Which method do you advise

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I m seeing various bits and pieces of the right answer here  but let me bring it all together and explain a couple of things   First of all  AcceptChanges should only be used to mark the entire transaction on a table as being validated and committed  Which means if you are using the DataTable as a DataSource for binding to  for example  an SQL server  then calling AcceptChanges manually will guarantee that that the changes never get saved to the SQL server   What makes this issue more confusing is that there are actually two cases in which the exception is thrown and we have to prevent both of them   1  Modifying an IEnumerable s Collection  We can t add or remove an index to the collection being enumerated because doing so may affect the enumerator s internal indexing  There are two ways to get around this  either do your own indexing in a for loop  or use a separate collection  that is not modified  for the enumeration   2  Attempting to Read a Deleted Entry  Since DataTables are transactional collections  entries can be marked for deletion but still appear in the enumeration  Which means that if you ask a deleted entry for the column  name  then it will throw an exception  Which means we must check to see whether dr RowState    DataRowState Deleted before querying a column   Putting it all together  We could get messy and do all of that manually  or we can let the DataTable do all the work for us and make the statement look and at more like an SQL call by doing the following   string name    Joe   foreach DataRow dr in dtPerson Select   name   name          dr Delete      By calling DataTable s Select function  our query automatically avoids already deleted entries in the DataTable  And since the Select function returns an array of matches  the collection we are enumerating over is not modified when we call dr Delete    I ve also spiced up the Select expression with string interpolation to allow for variable selection without making the code noisy

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Before everyone jumps on the  You can t delete rows in an Enumeration  bandwagon  you need to first realize that DataTables are transactional  and do not technically purge changes until you call AcceptChanges    If you are seeing this exception while calling Delete  you are already in a pending-changes data state   For instance  if you have just loaded from the database  calling Delete would throw an exception if you were inside a foreach loop     BUT  BUT   If you load rows from the database and call the function  AcceptChanges    you commit all of those pending changes to the DataTable   Now you can iterate through the list of rows calling Delete   without a care in the world  because it simply ear-marks the row for Deletion  but is not committed until you again call AcceptChanges    I realize this response is a bit dated  but I had to deal with a similar issue recently and hopefully this saves some pain for a future developer working on 10-year-old code       P s  Here is a simple code example added by Jeff   C        YourDataTable AcceptChanges     foreach  DataRow row in YourDataTable Rows           If this row is offensive then     row Delete       YourDataTable AcceptChanges      VB Net      ds Tables 0  AcceptChanges   For Each row In ds Tables 0  Rows     ds Tables 0  Rows counter  Delete       counter    1 Next ds Tables 0  AcceptChanges

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the easy way use this in button    var table       example1   DataTable     table row     yesmediasec-  id    closest  tr    remove    draw     example1   id table   yesmediasec   id of the button in the row use it and every thing will be ok

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Where is the problem  It is forbidden to delete items from collection inside a foreach loop   Solution  Either do it like Widor wrote  or use two loops  In the first pass over DataTable you only store  in a temporary list  the references to rows you want to delete  Then in the second pass over your temporary list you delete those rows

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lt asp GridView ID  grd item list  runat  server  AutoGenerateColumns  false  Width  100   CssClass  table table-bordered table-hover  OnRowCommand  grd item list RowCommand  gt       lt Columns gt           lt asp TemplateField HeaderText  No  gt               lt ItemTemplate gt                   lt    Container DataItemIndex   1   gt               lt  ItemTemplate gt           lt  asp TemplateField gt                       lt asp TemplateField HeaderText  Actions  gt               lt ItemTemplate gt                                       lt asp Button ID  remove itemIndex  OnClientClick  if confirm  Are You Sure to delete     true   return true   else  return false    runat  server  class  btn btn-primary  Text  REMOVE  CommandName  REMOVE ITEM  CommandArgument   lt    Container DataItemIndex 1   gt     gt               lt  ItemTemplate gt           lt  asp TemplateField gt       lt  Columns gt   lt  asp GridView gt      This is the row binding event    protected void grd item list RowCommand object sender  GridViewCommandEventArgs e         item list bind structure         if  ViewState  item list      null          dt    DataTable ViewState  item list          if  e CommandName     REMOVE ITEM             var RowNum   Convert ToInt32 e CommandArgument ToString    - 1           DataRow dr   dt Rows RowNum           dr Delete                grd item list DataSource   dt      grd item list DataBind

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You try this for getting and removing id column from data table  if  dt1 Columns Contains  ID          for  int i   dt1 Rows Count - 1  i  gt   0  i--                DataRow dr   dt1 Rows i            if  dr  ID   ToString          amp  amp  dr  ID   ToString      null                        dr Delete                         dt1 Columns Remove  ID

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I know this is  very  old question  and I have similar situation few days ago   Problem was  in my table are approx  10000 rows  so looping trough DataTable rows was very slow   Finally  I found much faster solution  where I make copy of source DataTable with desired results  clear source DataTable and merge results from temporary DataTable into source one   note   instead search for Joe in DataRow called name You have to search for all records whose not have name Joe  little opposite way of searching   There is example  vb net      Copy all rows into tmpTable whose not contain Joe in name DataRow Dim tmpTable As DataTable   drPerson Select  name lt  gt  Joe    CopyToTable  Clear source DataTable  in Your case dtPerson dtPerson Clear    merge tmpTable into dtPerson  rows whose name not contain Joe  dtPerson Merge tmpTable  tmpTable   Nothing   I hope so this shorter solution will help someone   There is c  code  not sure is it correct because I used online converter          Copy all rows into tmpTable whose not contain Joe in name DataRow DataTable tmpTable   drPerson Select  name lt  gt  Joe    CopyToTable    Clear source DataTable  in Your case dtPerson dtPerson Clear      merge tmpTable into dtPerson  rows whose name not contain Joe  dtPerson Merge tmpTable   tmpTable   null    Of course  I used Try Catch in case if there is no result  for example  if Your dtPerson don t contain name Joe it will throw exception   so You do nothing with Your table  it stays unchanged

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Or just convert a DataTable Row collection to a list   foreach DataRow dr in dtPerson Rows ToList          if dr  name   ToString     Joe       dr Delete

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To remove entire row from DataTable   do like this  DataTable dt   new DataTable       User DataTable DataRow   rows  rows   dt Select  UserName    KarthiK         UserName  is ColumnName foreach  DataRow row in rows       dt Rows Remove row

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with this solution   for int i   dtPerson Rows Count-1  i  gt   0  i--          DataRow dr   dtPerson Rows i        if  dr  name       Joe           dr Delete         if you are going to use the datatable after deleting the row  you will get an error  So what you can do is  replace dr Delete    with dtPerson Rows Remove dr

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If you delete an item from a collection  that collection has been changed and you can t continue to enumerate through it    Instead  use a For loop  such as   for int i   dtPerson Rows Count-1  i  gt   0  i--        DataRow dr   dtPerson Rows i       if  dr  name       Joe           dr Delete      dtPerson AcceptChanges      Note that you are iterating in reverse to avoid skipping a row after deleting the current index

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DataRow   dtr dtPerson select  name Joe    foreach var drow in dtr       drow delete      dtperson AcceptChanges      I hope it will help you

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This works for me   List lt string gt  lstRemoveColumns   new List lt string gt       ColValue1    ColVal2    ColValue3    ColValue4     List lt DataRow gt  rowsToDelete   new List lt DataRow gt      foreach  DataRow row in dt Rows        if  lstRemoveColumns Contains row  ColumnName   ToString               rowsToDelete Add row            foreach  DataRow row in rowsToDelete        dt Rows Remove row      dt AcceptChanges

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I have a dataset in my app and I went to set changes  deleting a row  to it but ds tabales  TableName   is read only  Then I found this solution   It s a wpf C  app   try       var results   from row in ds Tables  TableName   AsEnumerable   where row Field lt string gt   Personalid       47  select row                      foreach  DataRow row in results            ds Tables  TableName   Rows Remove row

[c#] Deleting specific rows from DataTable

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