title: Auto Select parameter Value if only one value
body: <p>I want a dynamic parameter whereas if it's referencing a dataset, if the data set returns only one record, then the param dropdown just shows that value.  But if the dataset returns multiple values for that parameter, then I want to show an initial "Select a value" or something like that as the first value in the dropdown before the list of values returned from the data set.</p>
  
  <p>I can't figure out how to do a conditional default value.  So somehow check the dataset count and if > 1 set the default value to "Select a Value".</p>
  
  <p>I'm not sure if I need to set the default value to do this even...anyone?</p>
  
  <p>I tried to select "specify values" in the default value tab of the Report Param and tried setting it to check for more than one record returned from the dataset and if so, add the default value of "Select a value" but this doesn't work:</p>
  
  <pre><code> =IIf(Count(Fields!BusinessLine.Value) &gt; 1, "Select a Value", First(Fields!BusinessLine))
  </code></pre>
  
  <p>I also tried:</p>
  
  <pre><code>=IIf(Parameters!Organization.Count &gt; 1, "Select a Value", First(Fields!BusinessLine))
  </code></pre>
  
  <p>no luck.  I get the error "A value expression used for the report parameter '@ParameterName' refers to a field.  Fields cannot be used in report parameter expressions."</p>
  
  <p>So I'm stuck here as to how to get this expression or check in here for the default selected value for my Report Parameter here. </p>