title: Crystal Report Windows Forms Viewer : Object Reference not set to an instance on an object
body: <p>I am working with a Crystal Reports in Vb.Net Forms application. A huge report that consists of 10-12 Sub-Reports,there are many formulas used in this report, sometimes this report shows "Object Reference not set to an instance on an object" I can't figure out, I have handled exceptions as well. When I click to "Next Page" button it shows below dialog.</p>
  
  <p><img src="https://i.stack.imgur.com/5ht5F.jpg" alt="Error"></p>
  
  <p>I can't figure out why its happening.
  read many blogs, some says, its formula error, some says, "Mouse Move" error.</p>
  
  <p>Below is the code I have added, i will check now</p>
  
  <pre><code> Private Sub CrystalReportViewer1_HandleException(ByVal source As _
  Object, ByVal e As CrystalDecisions.Windows.Forms.ExceptionEventArgs) _
  Handles CrystalReportViewer1.HandleException
  
  'Label1.Text = e.Exception.ToString();
  'Here I will trap.
  
  End Sub
  </code></pre>
  
  <p>Below is the stack trace I have found by applying above code for exception:</p>
  
  <pre><code>Source:CrystalDecisions.CrystalReports.Engine
  Message:Object reference not set to an instance of an object.
  ST:   at CrystalDecisions.CrystalReports.Engine.ReportDocument.get_IsLoaded()
  at CrystalDecisions.ReportSource.NonHTTPCachedReportSource.GetReport(RequestContext  context, Boolean bAddToCacheWhenCreated)
  at CrystalDecisions.ReportSource.LocalReportSourceBase.GetPage(PageRequestContext pageReqContext)
  at CrystalDecisions.Windows.Forms.MainReportDocument.GetPage(PageRequestContext context)
  </code></pre>