[C#] Remove null checks for C# value types

[etherealjoy]

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Description of the PR

Remove null checks on C# value types which throws a lot of warnings.

Null checks on enums which is a value type are already avoided. Combining simple types and enum as value types and avoiding null checks.
See here.
https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/value-types

@wing328 @mandrean @jimschubert

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[etherealjoy]

I will regenerate code if it looks OK

[etherealjoy]

Question:
why is this line (some lines above) not covering all enums

for (CodegenProperty var : model.allVars) 

I had to add a separate one for this below

for (CodegenProperty var : model.vars) {

[wing328]

It should. That could be a bug with allVars.

I'll look into it in the coming week.

[etherealjoy]

I think I need to add extra condition if it is a valueType but not nullable, however I see parsing of the nullable field is not done.
On the other hand I am checking the dataType so at this point if a nullable type is specified it won't be a valueType anymore.

[wing328]

You mean something like {{#isNullable}} ... {{/isNulalble}}?

[etherealjoy]

Exactly. So if the value is nullable it will not be e.g. int but int?. But in this case if the dataType is used for postprocess it is not anymore a valueType
I will try out some specs with nullable fields.

[wing328]

I think nullable is supported in the C# generators already: https://github.com/OpenAPITools/openapi-generator/pulls?utf8=%E2%9C%93&q=is%3Apr+is%3Amerged+nullable+csharp

but you will need to use x-nullable in OAS v2 instead which does not support nullable natively.

[etherealjoy]

Thank you. I see that the simple type is already changed to nullable type. Then this will be covered.
I will make the test with this.

[etherealjoy]

Ok, I verified it. the nullable types are having null checks. only value Types are skipped.

[wing328]

Can you please update the C# netcore sample as well?

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   samples/client/petstore/csharp-netcore/OpenAPIClient/docs/EnumTest.md
	modified:   samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/ApiResponse.cs
	modified:   samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/Cat.cs
	modified:   samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/CatAllOf.cs
	modified:   samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/Category.cs
	modified:   samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/EnumTest.cs
	modified:   samples/client/petstore/csharp-netcore/OpenAPIClient/src/Org.OpenAPITools/Model/FormatTest.cs