ASP.NET: DropDownList throws an exception “[ctlName] has a SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value”

 

Yes, you may monitor this exception if your DropDownList WebControl is initialized programmatically, like

ddlDocumentState.DataValueField = "StateId";
ddlDocumentState.DataTextField = “StateName";
ddlDocumentState.DataSource = stateList;
ddlDocumentState.DataBind(); // <— here is exception thrown

If the data source doesn’t include an element with empty string as value, the above mentioned exception is thrown.

The problem is solved with setting SelectedValue of the DropDownList to null:

ddlDocumentState.DataValueField = "StateId";
ddlDocumentState.DataTextField = “StateName";
ddlDocumentState.SelectedValue = null; // <- added to solve 

                                       // the problem
ddlDocumentState.DataSource = stateList;
ddlDocumentState.DataBind(); // <— here is no more exception

Enjoy!