System.Xml.Serialization.XmlSerializer.XmlSerializer() is inaccessible due to its protection level

One reason for this error is if you haven't mentioned the type when you initialize the XmlSerializer object

XmlSerializer Xser = new XmlSerializer()

can be replaced with

XmlSerializer Xser = new XmlSerializer(this.GetType() );

Unable to copy file "obj\x86\Debug\*.exe" to "bin\Debug\*.exe". The process cannot access the file 'bin\Debug\*.exe' because it is being used by another process.

To release the file go to the Task Manager and see if the Exe is running in the process Tab. Kill the process and Build the project it should work.

But before that make sure why the Exe was still running in the process even after the application is termninated. It might be due to some malperformance of garbage collection