title: Passing optional parameters
body: <p>I am working on SSRS Reporting Services with 2008R2. </p>
  
  <p>ISSUE: I have two tables <code>Orders</code> and <code>Customers</code>.</p>
  
  <p>I join both the tables and get the sufficient data.</p>
  
  <p>My issue is how to pass <code>Customername</code> as optional parameter. I need to take this value from a query (I mean to display customer name in drop down).</p>
  
  <p>To do this I have checked allow nulls as true for the parameter name: Customer name. But while generating the report it asks to select customer name. </p>
  
  <p>I have also tried with:</p>
  
  <p>Specified the filter condition of the dataset as follows:</p>
  
  <p><strong>Expression</strong>:</p>
  
  <pre><code>=IIF(Parameters!CustomerName.Value is nothing or (Fields!CustomerName.Value =Parameters!CustomerName.Value),true,false)  
  </code></pre>
  
  <p>(Select <code>Boolean</code> in the second drop-down list)</p>
  
  <p><strong>Operator</strong>: <code>=</code></p>
  
  <p><strong>Value</strong>: <code>true</code></p>