Add project files and fix warnings

[gewarren]

Add missing project files and fix some warnings. Also modernize code.

[learn-build-service-prod]

Learn Build status updates of commit be58c9c:

✅ Validation status: passed

File	Status	Preview URL	Details
snippets/csharp/System.Messaging/MessageQueue/.ctor/class1.cs	✅Succeeded	View
snippets/csharp/System.Messaging/MessageQueue/.ctor/class11.cs	✅Succeeded	View
snippets/csharp/System.Messaging/MessageQueue/.ctor/mqctor_denysharedreceive.cs	✅Succeeded	View
snippets/csharp/System.Messaging/MessageQueue/.ctor/Project.csproj	✅Succeeded
snippets/csharp/System.Messaging/MessageQueue/BeginPeek/mqbeginpeek_noparms.cs	✅Succeeded	View
snippets/csharp/System.Messaging/MessageQueue/BeginPeek/mqbeginpeek_timeout.cs	✅Succeeded	View
snippets/csharp/System.Messaging/MessageQueue/BeginPeek/mqbeginpeek_timeoutstateobject.cs	✅Succeeded	View
snippets/csharp/System.Messaging/MessageQueue/BeginPeek/Project.csproj	✅Succeeded
snippets/csharp/System.Net.Sockets/MulticastOption/Overview/listener.cs	✅Succeeded	View
snippets/csharp/System.Net.Sockets/MulticastOption/Overview/Project.csproj	✅Succeeded
snippets/csharp/System.Net.Sockets/MulticastOption/Overview/sender.cs	✅Succeeded	View
snippets/csharp/System.Reflection.Emit/EnumBuilder/GetCustomAttributes/enumbuilder_setcustomattribute2.cs	✅Succeeded	View
snippets/csharp/System.Reflection.Emit/EnumBuilder/GetCustomAttributes/Project.csproj	✅Succeeded
snippets/csharp/System.Runtime.InteropServices/ComImportAttribute/Overview/codefile1.cs	✅Succeeded	n/a (file deleted or renamed)
snippets/csharp/System.Runtime.InteropServices/ComImportAttribute/Overview/codefile2.cs	✅Succeeded	View
snippets/csharp/System.Runtime.InteropServices/ComImportAttribute/Overview/codefile3.cs	✅Succeeded	View
snippets/csharp/System.Runtime.InteropServices/ComImportAttribute/Overview/codefile4.cs	✅Succeeded	View
snippets/csharp/System.Runtime.InteropServices/ComImportAttribute/Overview/codefile5.cs	✅Succeeded	View
snippets/csharp/System.Runtime.InteropServices/ComImportAttribute/Overview/Project.csproj	✅Succeeded
snippets/csharp/System.Runtime.InteropServices/Marshal/GetActiveObject/Project.csproj	✅Succeeded
snippets/csharp/System.Security.Cryptography/AsymmetricKeyExchangeDeformatter/Overview/contosodeformatter.cs	✅Succeeded	View
snippets/csharp/System.Security.Cryptography/AsymmetricKeyExchangeDeformatter/Overview/ContosoEncryption.cs	✅Succeeded	n/a (file deleted or renamed)
snippets/csharp/System.Security.Cryptography/AsymmetricKeyExchangeDeformatter/Overview/makefile	✅Succeeded	n/a (file deleted or renamed)
snippets/csharp/System.Security.Cryptography/AsymmetricKeyExchangeDeformatter/Overview/Project.csproj	✅Succeeded
snippets/csharp/System.Windows.Forms/KeyPressEventArgs/Handled/Project.csproj	✅Succeeded

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[BillWagner]

Thias LGTM @gewarren

Let's

[gewarren]

@BillWagner Can you approve it so I can merge it?

[BillWagner]

I accidentally clicked "comment" instead of "approve" earlier.