I recently was asked about a problem in the SalesLogix web client where the Bill To Ship To tab throws an error if either the Bill To or Ship To contact has more than one address with the same description.

If you look at the load event of the form you can see it is using a code action item like this:

        System.Web.UI.WebControls.ListItem billingItem;
        lstbxBillingAddress.Items.Clear();
        if (salesOrder.BillingContact != null)
        {
            System.Collections.Generic.IList<Sage.Entity.Interfaces.IAddress> billingAddresses = Sage.Platform.EntityFactory.GetRepository<Sage.Entity.Interfaces.IAddress>().FindByProperty("EntityId", salesOrder.BillingContact.Id.ToString());
            if (billingAddresses != null)
            {
                foreach (Sage.Entity.Interfaces.IAddress address in billingAddresses)
                {
                    billingItem = new System.Web.UI.WebControls.ListItem();
                    billingItem.Text = address.Description;
                    billingItem.Value = address.Id.ToString();
                    billingItem.Selected = address.Description.Equals(salesOrder.BillingAddress.Description);
                    lstbxBillingAddress.Items.Add(billingItem);
                }
            }
        }

The problem is in the line shown above in red, where the are selecting the address in the list based on if it is the same description as the sales order's address.  Since this is a single select list box it will not allow you to multi-select the same description if it exists.

A work around is to handle catching if an address has already been selected. Like so:

            System.Web.UI.WebControls.ListItem billingItem;
            lstbxBillingAddress.Items.Clear();
            if (salesOrder.BillingContact != null)
            {
                Sage.Platform.RepositoryHelper<Sage.Entity.Interfaces.IAddress> repository = Sage.Platform.EntityFactory.GetRepositoryHelper<Sage.Entity.Interfaces.IAddress>();
                Sage.Platform.Repository.ICriteria criteria = repository.CreateCriteria();
                criteria.Add(repository.EF.Eq("EntityId", salesOrder.BillingContact.Id.ToString()));
                criteria.AddOrder(repository.EF.Asc("Description"));
                System.Collections.Generic.IList<Sage.Entity.Interfaces.IAddress> billingAddresses = criteria.List<Sage.Entity.Interfaces.IAddress>();
                //System.Collections.Generic.IList<Sage.Entity.Interfaces.IAddress> billingAddresses = Sage.Platform.EntityFactory.GetRepository<Sage.Entity.Interfaces.IAddress>().FindByProperty("EntityId", salesOrder.BillingContact.Id.ToString());
                if (billingAddresses != null)
                {
                    bool selection = false;
                    foreach (Sage.Entity.Interfaces.IAddress address in billingAddresses)
                    {
                        billingItem = new System.Web.UI.WebControls.ListItem();
                        billingItem.Text = address.Description;
                        billingItem.Value = address.Id.ToString();
                        if (address.Description.Equals(salesOrder.BillingAddress.Description) && !selection)
                        {
                            billingItem.Selected = true;
                            selection = true;
                        }
                        lstbxBillingAddress.Items.Add(billingItem);
                    }
                }
            }

The pertinent changes to the code are shown in red. 

Also note, in the green lines, I have also modified the code to retrieve the list of addresses sorted alphabetically by description, unlike the OOTB screen which has no sort.

A pretty easy fix to make to the screen to let you work with contacts having the same description.  If you do have a lot of the same descriptions for addresses, it might be worth adding some additional descriptive information into the list, like

billingItem.Text = address.Description + " - " + address.City;