title: set values in web.config dynamically?
body: <p>in my web.config I have things like:</p>
  
  <pre><code> &lt;connectionStrings&gt;
      &lt;add name="Entities1" connectionString="metadata=res://*/CData.csdl|res://*/CData.ssdl|res://*/CData.msl;provider=System.Data.SqlClient;provider connection string=&amp;quot;data source=ser;initial catalog=dda;persist security info=True;user id=s;password=a;multipleactiveresultsets=True;App=EntityFramework&amp;quot;" providerName="System.Data.EntityClient" /&gt;
      &lt;add name="Entities2" connectionString="metadata=res://*/M.AuthModel.csdl|res://*/M.AuthModel.ssdl|res://*/M.AuthModel.msl;provider=System.Data.SqlClient;provider connection string=&amp;quot;data source=ser;initial catalog=dda;persist security info=True;user id=s;password=a;multipleactiveresultsets=True;App=EntityFramework&amp;quot;" providerName="System.Data.EntityClient" /&gt;
    &lt;/connectionStrings&gt;
  </code></pre>
  
  <p>where I have things like the DB password and so on.</p>
  
  <p>Every time I create a setting in my Project, I get s.th. like:</p>
  
  <pre><code>&lt;setting name="db_username" serializeAs="String"&gt;
          &lt;value&gt;s&lt;/value&gt;
  &lt;/setting&gt;
  </code></pre>
  
  <p>is it possible to user this <code>setting</code> in the <code>connectionString</code> above so that I can change e.g. the Username for both with just changing the <code>setting</code>?</p>