I have a problem with listbox

[StoaVio]

Iam facing a problem in adding a value to a list box which is located in parent window thru a child window. I made the listbox as HTML control and the following is the code i have written in the child window to add a value in it.

When i clicked the submit button of child window it throws a error "Server threws an exception" and the window is get closed.

Plz help me!!.

[Dodge]

First, please provide the complete text of the exception.

Second, please simplify this in order to create a small reproducer. For instance, does the DataGrid have to be on the child form in order for you to reproduce the problem?

[Dodge]

The parent window contains a listbox (HTML) and a button called "Add", once the user clicks the Add button a child window popups up with a datagrid ontains a series of values and checkbox and a single submit button, once the user selects his required values thru checking checkboxes and clicks the submit button the selected values has to be added into the parent window's listbox.

I hope, this is clear as far as the functionality required here.