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adding rows from one datatable to another

The following code :
For Each r As DataRow In dtFlow.Rows
Dim arow As DataRow = dtAllFlows.NewR ow
arow = r
dtAllFlows.Rows .Add(arow)

leads to the error 'This row already belongs to another table '
at the line dtAllFlows.Rows .Add(arow).
I guess I should just do dtAllFlows = dtFlow.copy, but I can't as the
code above is contained in a For loop and at each iteration, I add new
rows (dtFlow changes at each iteration).

How can I solve this problem ?


Nov 21 '05
21 22744
I read your message but :

1. the link u gave me does not work
2. I don't understand this sentence :

The only thing you can do is copy it, use an extra dataview, remove it
the first.

Could you explain that to me if you don't mind please ?


Nov 21 '05 #11


You cannot add a reference from a datarow to 2 datatables. (That is what you
do with Add or insertAt)

Therefore is the only thing that you can do.
Create a copy from the original and add that to your new table
Remove the reference from the first and than add it to the new table
Create an extra dataview instead of that extra table.

The copy you have already, the second seems for me out of sense and the
thirth is probably what you need.

dim dv as new dataview(mydata table)

In fact you have now a complete view on your table. If you want only some
rows than you need a rowfilter

dv.rowfilter = "City = 'Amsterdam'"

I hope this helps

Nov 21 '05 #12
I'm very very confused. Sorry :(
Are you actually saying I should do that :

1. Create a copy from the original and add that to your new table
dim dtAllFlows as datatable
dtAllFlows = dtFlow.copy

2.Remove the reference from the first and than add it to the new table
???? what does this mean ?

3. Create an extra dataview instead of that extra table.
What for ? :
Dim dvTmp As new DataView
dvTmp.Table = dtFlow

Could you give a very simple example please, as I really don't
understand the above ?
Sorry for bothering :(

Nov 21 '05 #13

I am only saying that you cannot have the same datarow in 2 datatables.

However you only tell that you want this and I only try to explain you why
this is impossible.

Nov 21 '05 #14
I understood this. But you've also tried to explain a work around and I
dont understand it !

You said :
Therefore is the only thing that you can do.
Create a copy from the original and add that to your new table
Remove the reference from the first and than add it to the new table
Create an extra dataview instead of that extra table.
Could you give a little example of this (just a few lines of code) as I
can't get it.

Thx a lot

Nov 21 '05 #15

In addition, I give you 3 solutions that can solve your problem. However I
don't know your problem except that an original row cannot be added.

Nov 21 '05 #16

Quickly writen in this messages so watch typos or others.

The first
dim dtnew as datatable = dtOld.Clone
dtnew.rows.Add( dt.newrow)
dtnew.importrow (dtOld.Rows(0))
The second
dim dtnew as datatable = dtOld.Clone
dtnew.rows.Add( dt.newrow)
dim dr as datarow = dtnew.rows(0)
dt.rows.remove( 0)
dtnew.rows.Add( dr)
The third
dim dv = new dataview(dtOld)
'in a dv the show on a datarow is to get (as I showed you before) as a

I hope this give some ideas

Nov 21 '05 #17

All of these three methods have an issue.
As I said before, my code is in a loop. I think it's a good idea I give
the algorithm I'm trying to write so one can help me :

for ........
'reset dtFlows
'fill dtFlows with values based on some requests

'add rows of dtFlows to dtAllFlows (I know I can't do that directely)

Therefore, doing one of your two methods wouldn't work as I don't want
to do
dim dtnew as datatable = dtOld.Clone in each loop (that would delete
all the existing rows added before)
Your third method :
dim dv = new dataview(dtOld)
OK but I want to put my dv in a datatable then, how ? Actually to be
more precise, I want to add this new datatable (dataview) to a dataset.

Hope I'm clear enough.


Nov 21 '05 #18

You mean that you want to do this

Dim ds as new dataset
ds.tables.add(t ableOld.copy)

Here the same isue, you cannot add a table to two dataset, because every
datatable has a property dataset which can only hold one dataset.


I know it is hard, I cannot change it.

Nov 21 '05 #19
NOOOOOOOOOOOO !!!!!!! :-) I think we'll never understand each other on
this one, LOL
I don't want to add a table to two datasets. I just want to :

reset datatable
fill datatable with data

fill newdatatable with rows of datatable above (here is the catch and
I must find another way to do it, as you explained with a lot of effort
that it's impossible ;-))


Then add newdatatable to a dataset (this is no problem at all)

Hope this is clear ! Again as I'm in a loop I cannot do
dim dtnew as datatable = dtOld.Clone
as you mentionned before otherwise I would loose the data stored in
dtnew that have been added in previous loops.


Nov 21 '05 #20

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