SelectedValue is invalid - doesn't exist in list - C#/ASP.NET
<p>Exception is: 
'Country' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value</p>

<pre><code>UserService.DsUserAttributes dsCountry = us_service.GetUserAttributeDropDown(systemId, "Country");
Country.DataSource = dsCountry.tblDropDownValues;
Country.DataTextField = "AttrValue";
Country.DataValueField = "Id";
Country.DataBind();
</code></pre>

<p>The values held within dsCountry.tblDropDownValues are:</p>

<pre><code>Id                                      AttrValue       AttrName
aefa28e0-a118-11dd-ad8b-080c210c9a66    PLEASE SELECT Country
213a743e-ea0b-419c-bd44-03b1c35241b3    USA         Country
eefa1387-8dc0-11d8-975f-13da67a41a5d    CANADA         Country
</code></pre>
