title: How do you get a subreport to render in SSRS?
body: <p>I am wondering if someone can let me know which of the following steps I am doing wrong.</p>
  
  <ol>
  <li>Have a blank new report ('Blank')</li>
  <li>Have an existing report ('Sub1') which has its own
  data sources and one parameter (int, named 'Likelihood', with
  a default value). These are in the same project and same folder.</li>
  <li>Drag the subreport control onto the new report</li>
  <li>In the subreport control properties, select "Sub1" as the "Use this report as a subreport".</li>
  <li>In the parameters tab click Add.</li>
  <li>Try and select a name from the dropdown (it's empty).</li>
  <li>Enter 'Likelihood' as the name.</li>
  <li>Enter '1' as the value.</li>
  <li>Try and preview the report, get 'Error: Subreport could not be shown.' in the preview and 'rsErrorExecutingSubreport] An error occurred while executing the subreport 'SubReport1' (Instance: 0): Object reference not set to an instance of an object.' in the Output (where 'Subreport1' is the name of the control attempting to render the report 'Sub1'.</li>
  </ol>
  
  <p>Things I have tried:</p>
  
  <ol>
  <li>Entering '=1' as the value.</li>
  <li>Adding a parameter of the same type and name to my main report 'Blank'. Leaving Parameters tab blank in subreport control properties. Also tried setting the value of a 'Likelihood' entry to be equal to the parameter on the Blank report ('=Parameters!Likelihood.Value').</li>
  <li>Setting the name as '@Likelihood' (error about requiring name be CLR compliant).</li>
  <li>Copying the datasources and tables etc. from the subreport to the blank parent report.</li>
  </ol>
  
  <p>The SubReport control rdl:</p>
  
  <pre><code>&lt;Subreport Name="Subreport1"&gt;
      &lt;ReportName&gt;Sub1&lt;/ReportName&gt;
      &lt;Parameters&gt;
        &lt;Parameter Name="Likelihood"&gt;
          &lt;Value&gt;10&lt;/Value&gt;
        &lt;/Parameter&gt;
      &lt;/Parameters&gt;
      &lt;Top&gt;2cm&lt;/Top&gt;
      &lt;Left&gt;2cm&lt;/Left&gt;
      &lt;Height&gt;7cm&lt;/Height&gt;
      &lt;Width&gt;7cm&lt;/Width&gt;
      &lt;ZIndex&gt;1&lt;/ZIndex&gt;
      &lt;Style&gt;
        &lt;Border&gt;
          &lt;Style&gt;None&lt;/Style&gt;
        &lt;/Border&gt;
      &lt;/Style&gt;
    &lt;/Subreport&gt;
  </code></pre>
  
  <p>I have encountered many others with similar problems but I have not yet found a solution and would appreciate a point in the right direction.</p>