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

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It may be worth first databinding and then adding your blank value. Something along the lines of:

_ddlRequest.Datasource = request;
_ddlRequest.DataBind();
_ddlRequest.Insert(0, new ListItem("", ""));

The only reason I suggest this is that I came across this before and after banging my head in frustration for a while just settled on doing it this way instead.

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Mihai
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Mihai

Updated on June 04, 2022

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  • Mihai
    Mihai almost 2 years

    I have a ASP.NET DropDownList, which I data-bind to a list of objects, and then it throws an exception. This error is driving me nuts, because the message is wrong, and the value clearly does exist in the list of items, as shown by the screenshot: enter image description here

    Here's the relevant ASP.NET markup:

    <asp:DropDownList ID="_ddlRequests" runat="server" AppendDataBoundItems="true" DataTextField="RequestNumber" DataValueField="RequestNumber">
        <asp:ListItem Text="" Value="" />
    </asp:DropDownList>