Enumerators that need to be changed at runtime, avoiding exception

[Daniel]

Hi guys

In regards to the foreach and for loops. I am trying to avoid this
exception:exception:

"Collection was modified; enumeration operation may not execute.
System.InvalidOperationException"

The problem is i have a timer, that checks at an interval for any changes to
a list if there are changes it removes the corresponding item:

See below:

public override bool RemoveRoom(int roomId)
{
try
{
for (int i = 0; i < _roomList.Count; i++)
{
Room room = (Room)_roomList;

if (room.RoomId.Equals(roomId))
{
//clear timers
_timeManager.RemoveAll(roomId);

_roomList.RemoveAt(i);

return true;
}
}

return false;
}
catch(Exception e)
{
Console.WriteLine("Error removing room, exception: " +
e.Message + " " + e.GetType().ToString());
return false;
}
}

I understand why i am getting the error, i am changing the enumeratoed list
by removing an item durin the enumeration. So my question is, how do i do
this saftely?

Another issue i have is a render loop that runs in a for each liek this:

foreach(Object o in objList)
{
o.RenderObject();
}

And that runs all the time, but objects need to be removed from that list
when they are no longer 'alive'. Again how do i do that saftely?

Is the answer to lock it so that no other thread accesses it while the
object is removed? How would this hit efficiency is this even the right way
about it?

So to summarise, how do you remove an item from a list/array while it is
being looked through via a loop safetly? Thanks is advance

 

[John Duval]

Hi Daniel,
You might want to check out Eric Gunnerson's IterIsolate:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dncscol/html/Csharp01212002.asp

Hope that helps,
John

 

[Daniel]

WOW thanks!

Hi Daniel,
You might want to check out Eric Gunnerson's IterIsolate:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dncscol/html/Csharp01212002.asp

Hope that helps,
John

Hi guys

In regards to the foreach and for loops. I am trying to avoid this
exception:exception:

"Collection was modified; enumeration operation may not execute.
System.InvalidOperationException"

The problem is i have a timer, that checks at an interval for any changes
to
a list if there are changes it removes the corresponding item:

See below:

public override bool RemoveRoom(int roomId)
{
try
{
for (int i = 0; i < _roomList.Count; i++)
{
Room room = (Room)_roomList;

if (room.RoomId.Equals(roomId))
{
//clear timers
_timeManager.RemoveAll(roomId);

_roomList.RemoveAt(i);

return true;
}
}

return false;
}
catch(Exception e)
{
Console.WriteLine("Error removing room, exception: " +
e.Message + " " + e.GetType().ToString());
return false;
}
}

I understand why i am getting the error, i am changing the enumeratoed
list
by removing an item durin the enumeration. So my question is, how do i do
this saftely?

Another issue i have is a render loop that runs in a for each liek this:

foreach(Object o in objList)
{
o.RenderObject();
}

And that runs all the time, but objects need to be removed from that list
when they are no longer 'alive'. Again how do i do that saftely?

Is the answer to lock it so that no other thread accesses it while the
object is removed? How would this hit efficiency is this even the right
way
about it?

So to summarise, how do you remove an item from a list/array while it is
being looked through via a loop safetly? Thanks is advance

 

[William Stacey [C# MVP]]

I could be interesting to get same method working with Lists so you could
remove current and do the index fixup internally.

--
William Stacey [C# MVP]

| Hi Daniel,
| You might want to check out Eric Gunnerson's IterIsolate:
|
|
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dncscol/html/Csharp01212002.asp
|
| Hope that helps,
| John
|
| Daniel wrote:
| > Hi guys
| >
| > In regards to the foreach and for loops. I am trying to avoid this
| > exception:exception:
| >
| > "Collection was modified; enumeration operation may not execute.
| > System.InvalidOperationException"
| >
| > The problem is i have a timer, that checks at an interval for any
changes to
| > a list if there are changes it removes the corresponding item:
| >
| > See below:
| >
| > public override bool RemoveRoom(int roomId)
| > {
| > try
| > {
| > for (int i = 0; i < _roomList.Count; i++)
| > {
| > Room room = (Room)_roomList;
| >
| > if (room.RoomId.Equals(roomId))
| > {
| > //clear timers
| > _timeManager.RemoveAll(roomId);
| >
| > _roomList.RemoveAt(i);
| >
| > return true;
| > }
| > }
| >
| > return false;
| > }
| > catch(Exception e)
| > {
| > Console.WriteLine("Error removing room, exception: " +
| > e.Message + " " + e.GetType().ToString());
| > return false;
| > }
| > }
| >
| > I understand why i am getting the error, i am changing the enumeratoed
list
| > by removing an item durin the enumeration. So my question is, how do i
do
| > this saftely?
| >
| > Another issue i have is a render loop that runs in a for each liek this:
| >
| > foreach(Object o in objList)
| > {
| > o.RenderObject();
| > }
| >
| > And that runs all the time, but objects need to be removed from that
list
| > when they are no longer 'alive'. Again how do i do that saftely?
| >
| > Is the answer to lock it so that no other thread accesses it while the
| > object is removed? How would this hit efficiency is this even the right
way
| > about it?
| >
| > So to summarise, how do you remove an item from a list/array while it is
| > being looked through via a loop safetly? Thanks is advance
|

 

[Ignacio Machin \( .NET/ C# MVP \)]

Hi,

| Hi Daniel,
| You might want to check out Eric Gunnerson's IterIsolate:
|
|
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dncscol/html/Csharp01212002.asp
|
| Hope that helps,
| John

It did help me, it says how to show the console window in a win app, this is
a frequent question here and I did not know the answer