title: Expression illegal in evaluator
body: <p>I'm trying to code something but there is happening something I don't understand.</p>
  
  <p>I get some values from a database and loop over them and change some of them if needed.</p>
  
  <p>This is what I'm trying to do:</p>
  
  <pre><code>if qryGeneral.fieldbyname('B_PRIJS').IsNull or 
     qryGeneral.fieldbyname('B_PRIJS').Value = 0 then
  begin
     if (qryGeneral.fieldbyname('V_PRIJS').Value &lt;&gt; 0) or 
        (qryGeneral.fieldbyname('V_PRIJSEXCL').Value &lt;&gt; 0) then
     //make some calculations and save data
  end;
  </code></pre>
  
  <p><code>B_PRIJS</code> is a float, null type in a SQL Server DB. When I set a breakpoint and I hover .Value it shows 0,11. When I hover IsNull it shows False, so far so good.</p>
  
  <p>Now I would expect it would NOT enter the if-structure, because it is not null and not equal to 0, but it does enter the if-structure.
  I don't understand why, I always coded like this.</p>
  
  <p>When I select <code>qryGeneral.fieldbyname('B_PRIJS').Value = 0</code> while still being in debug mode, I get a message "Expression illegal in evaluator".</p>
  
  <p>I tried replacing <code>Value</code> into <code>AsFloat</code> or changing 0 into 0.0 but it doesn't work.</p>
  
  <p>What am I doing wrong or not understanding here?</p>