add back null check #296

Job	Run time
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare)	1m 13s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.7/Petstore)	1m 54s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.7/FormModels)	1m 9s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.7/AllOf)	1m 12s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare)	1m 14s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate)	1m 11s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.8/FormModels)	1m 41s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.7/AnyOf)	3m 39s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate)	1m 8s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.8/AllOf)	1m 13s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.7/OneOf)	1m 6s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.8/OneOf)	1m 18s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.8/Petstore)	1m 8s
Build .Net Framework projects (samples/client/petstore/csharp/generichost/net4.8/AnyOf)	1m 10s
	20m 16s

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