Fixed NullReferenceException.
Added test for optional {V}Specified and ShouldSerialize{V}.
{V}Specified is a property or field and ShouldSerialize{V} is a method that can be set to false if we do not want to serialize an attribute with name {V}.
Added optional serialization based on ShouldSerialize{V}.
SerializationCodeGenerator and XmlSerializationWriterInterpreter will no longer serialize an attribute named {V} if its object has a method named ShouldSerialize{V}() that returns false.
{V}Specified now is also checked to be true before serializating the attribute even if it is a property that is not settable.
Fixes #1852.
Test serialization wen class has method bool ShouldSerialize<T>().
.NET throws an exception but it should have no effect on the serialization.
Ignore method ShouldSerialize if it is a generic.
Merge pull request #1257 from esdrubal/xmloptional

Added optional serialization based on ShouldSerialize{V}.
[xbuild] Workaround for null log service (which should never be null)
Test xml serialization of nullable array items. Covers #19012.
If not specified assume that array items are nullable. Fixes #19012.
Merge pull request #1286 from esdrubal/xmlnullablearrayitem

XmlSerializer nullable array items.
[WCF]: Copy out/ref parameters on async call; bug #22129.
Merge pull request #1280 from nealef/master

Maximum large object size should be limited by SSIZE_MAX not SIZE_MAX.
[mcs] Revert usage of closed delegates for compiler generated anonymous method
Added missing files to projects csproj files.
[aot] Use gsharedvt for collection types instantiated with generic structs as well.
[xbuild] More tweaks to tool path setup
[runtime] Fix an assert in w32_dlerror () on winx64.
[arm64] Increase some opcode sizes. Fixes #23026.
[runtime] Add support for setting the thread name on windows. On windows, this will only work when running under a debugger.
[runtime] Fix the my_g_bit_nth_msf () function for win64.