Error Msg : Collection was modified: enumeration operation may not execute

[SonicWave]

Good day.

I have a datagrid which supposed to receive data input from user and when the user click on Save button, i use the function as below, to iterate throw each datarow and manually append it into db.

For Each objDR In tblUserGroupAdd.Rows
objUserGroup = New My.BusinessFacade.UserGroup

Select Case objDR.RowState
Case DataRowState.Added
objUserGroup.append(objDR("description", DataRowVersion.Default), objDR("remarks", DataRowVersion.Default), Nothing)
tblUserGroupAdd.RemoveTbl_User_GroupRow(objDR)

Case Else

End Select
Next

Upon success, teh datarow will be removed or else, it will remain in the datagrid.

But, when I try to exec the program, it return the error message "Collection was modified: enumeration operation may not execute".

What happen ? Is there any better way to code the same thing instead of the function I am using now ?

Thanks.

SonicWave

[SonicWave]

Good day.

I found an explaination in http://www.dotnet247.com/247referenc...31/158752.aspx saying that it's a problem with the looping.

But in another datagrid for the user to add, update adn delete existing data using the function below, it works flawlessly. I not really understand what happen.

For Each objDR In tblUserGroupAmmend.Rows
objUserGroup = New My.BusinessFacade.UserGroup

Select Case objDR.RowState
Case DataRowState.Added
objUserGroup.append(objDR("description", DataRowVersion.Proposed), objDR("remarks", DataRowVersion.Proposed), Nothing)

Case DataRowState.Deleted
objUserGroup.delete(objDR("id", DataRowVersion.Original), Nothing)
tblUserGroupAmmend.RemoveTbl_User_GroupRow(objDR)

Case DataRowState.Modified
objUserGroup.update(objDR("id"), objDR("description", DataRowVersion.Proposed), objDR("remarks", DataRowVersion.Proposed), Nothing)

Case Else

End Select
Next

Help.

SonicWave

[hellswraith]

When you affect the enumeration when using a foreach loop, things get messed up.

In order to modify contents in the way you are doing, you need to use a for loop, and loop in reverse. This won't mess with the elements that you are looping through.

The basic reason is you are modifying the elements you are looping through. When you do this, the iterator no longer knows what is next.