title: System.Web.HttpException: Cannot have multiple items selected in a DropDownList
body: <p>During page load, index 0 was already selected. Then this code statement selected index 1:</p>
  
  <pre><code>dropDownList.Items.FindByValue(myValue).Selected = true; 
  // assume myValue is found at index 1 of dropDownList.Items
  </code></pre>
  
  <p>On completion of page load, the page reads: "System.Web.HttpException: Cannot have multiple items selected in a DropDownList."</p>
  
  <p>Why did I get the exception? And how can I fix it?</p>