Since you mentioned that the thread, which is running elsewhere performs operation of the DataSource of the RadListBox (deleting items), do you rebind the RadListBox? The issue is probably related with the fact that the datasource of the RadListBox is changed, while you attempt to perform the reordering on the items, which does not already exist. Please make sure that the ListBox is supplied with the correct DataSource, with using the RadListBox1.DataBind()
. Thus, you will manually request the DataSource and you will ensure that this is the correct underlying data.
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