title: Filtering a DISTINCTCOUNT in DAX
body: <p>I have what I thought was a simple task: create a Measure that returns the distinct count of a field for all records that meet a specific filter condition, in this case a date filter. I came up with the following:</p>
  
  <pre><code>=CALCULATE(DISTINCTCOUNT(ExitFilter[Dim_Client_ID]),ExitFilter[ExitDate]&lt;1/1/2014)
  </code></pre>
  
  <p>and the result was (blank) so I tried:</p>
  
  <pre><code>=CALCULATE(DISTINCTCOUNT(ExitFilter[Dim_Client_ID]),FILTER(ExitFilter,ExitFilter[ExitDate]&lt;1/1/2014))
  </code></pre>
  
  <p>and the result was still (blank) so I tried:</p>
  
  <pre><code>=CALCULATE(COUNTROWS(DISTINCT(ExitFilter[Dim_Client_ID])),FILTER(ExitFilter,ExitFilter[ExitDate]&lt;1/1/2014))
  </code></pre>
  
  <p>and the result was still (blank). What am I missing? And what does (blank) signify?</p>
  
  <p>If it's not clear 'ExitFilter' is a table, [Dim_Client_Id] is a column, and [ExitDate] is a date column.</p>