How are you binding the data to the DropDownList?

>I have a detailsView in my webForm. Inside detailView have a dropdownlist.
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>The dropdownlist will be populated from a table eg, supplier table which have fields id,supName
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>The data source the detailsView is pulling data from another table which store supplier id.
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>If 2nd table store invalid supplier Id (eg. supplier deleted form supplier table or whatever), The error will appear :
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>System.ArgumentOutOfRangeException: 'DropDownList1' has a SelectedValue which is invalid because it does not exist in the list of items.
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>
>Any suggestions to solve the problem would be appreciated.
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>TIA.
>
>Best Regards,