ASP.NetControlsDropdownListVB.NetControlsDropdownList

ASP.Net DropDownList - Robust

Setting up DropDownList control to accomodate invalid values.

Does your dropdown control return messages like

DropDownList has a SelectedValue which is invalid because it does not exist in the list of item

Here’s an example of how to fix this

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<asp:DropDownList 
	 ID='ddl_Edit_codesLicensesAndCertsId'
	 runat='server'
	 cssClass='form-control'
	 DataSourceID='ods_codesLicensesAndCertsId'
	 DataTextField='description'
	 DataValueField='id'
	 SelectedValue='<%#Bind("codesLicensesAndCertsId")%>'
	 AppendDataBoundItems="true"
	 OnDataBinding="ddl_Edit_codesLicensesAndCertsId_DataBinding"
	 >
	<asp:ListItem Value="" Text="Select"></asp:ListItem>
</asp:DropDownList>

I added AppendDataBoundItems, OnDataBinding, and an extra ListItem

Then I created the OnDataBinding function

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Protected Sub ddl_Edit_codesLicensesAndCertsId_DataBinding(sender As Object, e As EventArgs)
	Dim ddList As DropDownList = CType(sender, DropDownList)
	RemoveHandler ddList.DataBinding, AddressOf ddl_Edit_codesLicensesAndCertsId_DataBinding
	Try
		ddList.DataBind()
	Catch ex As ArgumentOutOfRangeException
		ddList.SelectedValue = ""  ' or whatever value you have for the page dropdownlist
	End Try
End Sub

References:
https://blogs.uw.edu/earnshaw/2015/02/18/selected-value-invalid/