Error parsing AppSettings value with a query string

Question

In my AppSettings in web.config, I have something like this:

Answer 1

You can Try using & instead.

Answer 2

In XML an ampersand tells the parser "the data immediately following this ampersand is an entity which needs to be translated." If the data immediately following is not a valid XML entity, then you get this error. If possible, use & for your ampersand within the XML.

Answer 3

Replace & with & (escape it):

<add
    key="ExternalSystemUrl"
    value="http://domain.com/page.aspx?id={0}&amp;action=eat&amp;object=bacon" />

That's the common requirement for any valid XML file.

See Where can I get a list of the XML document escape characters?