How do I convert a PowerPoint file to PDF using Aspose 6.4?

[Heavy1]

I am using \[code\]aspose.slides.dll\[/code\] v6.4.0 to convert \[code\].pptx\[/code\] files to \[code\].pdf\[/code\].My Code:\[code\]public static MemoryStream pptx2Pdf(byte[] FileRead){ MemoryStream ResultStream = new MemoryStream(); Aspose.Slides.Pptx.PresentationEx pres = new Aspose.Slides.Pptx.PresentationEx(new MemoryStream(FileRead)); pres.Save(ResultStream, Aspose.Slides.Export.SaveFormat.Pdf); return ResultStream;}\[/code\]But when the method is called, the following exception is shown and file is not converted:\[quote\] Attempt by security transparent method 'ns3.Class115.smethod_6(System.Drawing.Imaging.BitmapData, Boolean)' to access security critical method 'System.Runtime.InteropServices.Marshal.Copy(IntPtr, Byte[], Int32, Int32)' failed. Assembly 'Aspose.Slides, Version=6.4.0.0, Culture=neutral, PublicKeyToken=null' is marked with the AllowPartiallyTrustedCallersAttribute, and uses the level 2 security transparency model. Level 2 transparency causes all methods in AllowPartiallyTrustedCallers assemblies to become security transparent by default, which may be the cause of this exception.\[/quote\]I tried to search for details about this exception, but could find nothing relevant to it. How can I resolve this issue?