title: nlog using the connectionStringName for database logging
body: <p>here is my nlog.config file. I have turned on the throwsException.</p>
  
  <pre><code>&lt;nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  throwExceptions="true"&gt;
        &lt;targets&gt;   
          &lt;target type="Database" name="databaseLog"
          dbProvider="sqlserver"   connectionstring="server=.\SQLExpress;database=Movie;integrated security=true"&gt;
              &lt;commandText&gt;
                  INSERT INTO [Log] ([Description] , [Level] ) VALUES (@Description,  @Level )
              &lt;/commandText&gt;
              &lt;parameter name="@Description" layout="${message}"/&gt; 
              &lt;parameter name="@Level" layout="${level}"/&gt;
          &lt;/target&gt;
  
        &lt;/targets&gt;
  
        &lt;rules&gt;
           &lt;logger name="*" minLevel="Trace"  appendTo="databaseLog"/&gt; 
        &lt;/rules&gt;
  &lt;/nlog&gt;
  </code></pre>
  
  <p>This will work and <em>will insert records into the database</em>. However I would like to use connectionstringName and not retype the connectionstring. 
  When I change the <strong><em>connectionstring</em></strong> to <strong><em>connectionstringname</em></strong> like this....</p>
  
  <pre><code>connectionstring="server=.\SQLExpress;database=Movie;integrated security=true"
  </code></pre>
  
  <p>to</p>
  
  <pre><code>connectionStringName="ApplicationConnectionString" 
  </code></pre>
  
  <p>I get an error 
  Expecting non-empty string for 'providerInvariantName' parameter</p>