title: blazor back end model exception just shows null?
body: <p>Primarily I am a Desktop developer, my interest was peaked by Blazor.  After having a play with the main sample I thought I create a Blazor Client app based off it.  But I am now suddenly experiencing some strange Exception and expression debug Evaluation behaviour?</p>
  <p>I've created a test Blazor Web Assembly application that uses VS2019 accesses a database using a simple Sql call through Dapper.  The object is created as part of the Control that renders the Page.</p>
  <p>The page auto-refreshes by triggering a timer every 1s.  And it works fine.  Until I call the SqlConnection create method, which fails with an error because the connection string is poorly formed.</p>
  <pre><code>        public bool DoTestSql(string sqlConn, string sqlCom)
          {
              SqlConnection conn = null;
              bool bok = false;
              try
              {
                  //this works
                  throw new Exception(&quot;Test Exception&quot;);
  
                  //this produces an Exception object but its very strange and is null???
  
                  conn = new SqlConnection(sqlConn);
  
                  //as a side node, going into immediate mode and typing ?sqlConn.subString(1) shows cannot be evaluated?
                  //?ex.ToString() shows &quot;unable to evaluate&quot;
                  bok = true;
              }
              catch (Exception ex)
              {
                  Debug.WriteLine(ex.ToString());
              }
  
              return bok;
  
          }
  
  </code></pre>
  <p>When the catch is caught (in the same function) it shows very little in the Exception object.  Printing the exception to console shows &quot;unable to evaluate&quot;.  In fact trying to output any variable in that function does the same.</p>
  <p>Once the connection string is correct I see &quot;Children could not be evaluated&quot; for the Exception?</p>
  <p>What is going on with the Exceptions and evaluations?  Is there any way round this?</p>
  <p>edit:  I have inserted a Sleep(10000) into the MainLayout.razor @code section to allow the debugger to spawn as per MS recommendation.</p>