Replace XmlTextWriter as it's not supported in NETCore (#642)
Replace XmlTextWriter as it's not supported in NETCore (#642)


pascalberger/docfx,LordZoltan/docfx,superyyrrzz/docfx,pascalberger/docfx,928PJY/docfx,LordZoltan/docfx,LordZoltan/docfx,dotnet/docfx,hellosnow/docfx,dotnet/docfx,dotnet/docfx,superyyrrzz/docfx,hellosnow/docfx,pascalberger/docfx,DuncanmaMSFT/docfx,LordZoltan/docfx,928PJY/docfx,928PJY/docfx,hellosnow/docfx,superyyrrzz/docfx,DuncanmaMSFT/docfx