diff --git a/core/data/tests/anonymous_struct_with_rename/output.cs b/core/data/tests/anonymous_struct_with_rename/output.cs
index d4e2f2da..84db6773 100644
--- a/core/data/tests/anonymous_struct_with_rename/output.cs
+++ b/core/data/tests/anonymous_struct_with_rename/output.cs
@@ -7,20 +7,27 @@
 
 /** Generated type representing the anonymous struct variant `List` of the `AnonymousStructWithRename` Rust enum */
 public class AnonymousStructWithRenameListInner {
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<string> list { get; set; }
 }
 
 /** Generated type representing the anonymous struct variant `LongFieldNames` of the `AnonymousStructWithRename` Rust enum */
 public class AnonymousStructWithRenameLongFieldNamesInner {
+	[JsonProperty(Required = Required.Always)]
 	public string some_long_field_name { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public bool and { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<string> but_one_more { get; set; }
 }
 
 /** Generated type representing the anonymous struct variant `KebabCase` of the `AnonymousStructWithRename` Rust enum */
 public class AnonymousStructWithRenameKebabCaseInner {
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<string> another-list { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public string camelCaseStringField { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public bool something-else { get; set; }
 }
 
diff --git a/core/data/tests/can_apply_prefix_correctly/output.cs b/core/data/tests/can_apply_prefix_correctly/output.cs
index 4608b126..c8129964 100644
--- a/core/data/tests/can_apply_prefix_correctly/output.cs
+++ b/core/data/tests/can_apply_prefix_correctly/output.cs
@@ -6,6 +6,7 @@
 using System.Runtime.Serialization;
 
 public class ItemDetailsFieldValue {
+	[JsonProperty(Required = Required.Always)]
 	public string Hello { get; set; }
 }
 
diff --git a/core/data/tests/can_generate_generic_enum/output.cs b/core/data/tests/can_generate_generic_enum/output.cs
index d7e26d9f..6d3adab1 100644
--- a/core/data/tests/can_generate_generic_enum/output.cs
+++ b/core/data/tests/can_generate_generic_enum/output.cs
@@ -16,6 +16,7 @@ public record VariantB(TB Content) : GenericEnum<TA, TB>();
 
 
 public class StructUsingGenericEnum {
+	[JsonProperty(Required = Required.Always)]
 	public GenericEnum<string, short> EnumField { get; set; }
 }
 
@@ -33,23 +34,29 @@ public record VariantE(GenericEnum<string, uint> Content) : GenericEnumUsingGene
 
 /** Generated type representing the anonymous struct variant `VariantF` of the `GenericEnumsUsingStructVariants` Rust enum */
 public class GenericEnumsUsingStructVariantsVariantFInner<T> {
+	[JsonProperty(Required = Required.Always)]
 	public T Action { get; set; }
 }
 
 /** Generated type representing the anonymous struct variant `VariantG` of the `GenericEnumsUsingStructVariants` Rust enum */
 public class GenericEnumsUsingStructVariantsVariantGInner<T, TU> {
+	[JsonProperty(Required = Required.Always)]
 	public T Action { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public TU Response { get; set; }
 }
 
 /** Generated type representing the anonymous struct variant `VariantH` of the `GenericEnumsUsingStructVariants` Rust enum */
 public class GenericEnumsUsingStructVariantsVariantHInner {
+	[JsonProperty(Required = Required.Always)]
 	public int NonGeneric { get; set; }
 }
 
 /** Generated type representing the anonymous struct variant `VariantI` of the `GenericEnumsUsingStructVariants` Rust enum */
 public class GenericEnumsUsingStructVariantsVariantIInner<T, TU> {
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<T> Vec { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public MyType<T, TU> Action { get; set; }
 }
 
diff --git a/core/data/tests/can_generate_readonly_fields/output.cs b/core/data/tests/can_generate_readonly_fields/output.cs
index 585b0e43..881d66ba 100644
--- a/core/data/tests/can_generate_readonly_fields/output.cs
+++ b/core/data/tests/can_generate_readonly_fields/output.cs
@@ -6,6 +6,7 @@
 using System.Runtime.Serialization;
 
 public class SomeStruct {
+	[JsonProperty(Required = Required.Always)]
 	public uint FieldA { get; set; }
 }
 
diff --git a/core/data/tests/can_generate_simple_struct_with_a_comment/output.cs b/core/data/tests/can_generate_simple_struct_with_a_comment/output.cs
index 744de2df..76a6dbd9 100644
--- a/core/data/tests/can_generate_simple_struct_with_a_comment/output.cs
+++ b/core/data/tests/can_generate_simple_struct_with_a_comment/output.cs
@@ -11,10 +11,14 @@ public class Location {
 /** This is a comment. */
 public class Person {
 	/** This is another comment */
+	[JsonProperty(Required = Required.Always)]
 	public string Name { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public ushort Age { get; set; }
 	public string? Info { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<string> Emails { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public Location Location { get; set; }
 }
 
diff --git a/core/data/tests/can_generate_slice_of_user_type/output.cs b/core/data/tests/can_generate_slice_of_user_type/output.cs
index 8696141c..95de631c 100644
--- a/core/data/tests/can_generate_slice_of_user_type/output.cs
+++ b/core/data/tests/can_generate_slice_of_user_type/output.cs
@@ -6,6 +6,7 @@
 using System.Runtime.Serialization;
 
 public class Video {
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<Tag> Tags { get; set; }
 }
 
diff --git a/core/data/tests/can_generate_struct_with_skipped_fields/output.cs b/core/data/tests/can_generate_struct_with_skipped_fields/output.cs
index a469a34b..da974387 100644
--- a/core/data/tests/can_generate_struct_with_skipped_fields/output.cs
+++ b/core/data/tests/can_generate_struct_with_skipped_fields/output.cs
@@ -6,7 +6,9 @@
 using System.Runtime.Serialization;
 
 public class MyStruct {
+	[JsonProperty(Required = Required.Always)]
 	public int A { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public int C { get; set; }
 }
 
diff --git a/core/data/tests/can_handle_anonymous_struct/output.cs b/core/data/tests/can_handle_anonymous_struct/output.cs
index 3ed38536..c93bb1bf 100644
--- a/core/data/tests/can_handle_anonymous_struct/output.cs
+++ b/core/data/tests/can_handle_anonymous_struct/output.cs
@@ -8,14 +8,17 @@
 /** Generated type representing the anonymous struct variant `Us` of the `AutofilledBy` Rust enum */
 public class AutofilledByUsInner {
 	/** The UUID for the fill */
+	[JsonProperty(Required = Required.Always)]
 	public string Uuid { get; set; }
 }
 
 /** Generated type representing the anonymous struct variant `SomethingElse` of the `AutofilledBy` Rust enum */
 public class AutofilledBySomethingElseInner {
 	/** The UUID for the fill */
+	[JsonProperty(Required = Required.Always)]
 	public string Uuid { get; set; }
 	/** Some other thing */
+	[JsonProperty(Required = Required.Always)]
 	public int Thing { get; set; }
 }
 
@@ -34,12 +37,15 @@ public record SomethingElse(AutofilledBySomethingElseInner Content): AutofilledB
 
 /** Generated type representing the anonymous struct variant `AnonVariant` of the `EnumWithManyVariants` Rust enum */
 public class EnumWithManyVariantsAnonVariantInner {
+	[JsonProperty(Required = Required.Always)]
 	public string Uuid { get; set; }
 }
 
 /** Generated type representing the anonymous struct variant `AnotherAnonVariant` of the `EnumWithManyVariants` Rust enum */
 public class EnumWithManyVariantsAnotherAnonVariantInner {
+	[JsonProperty(Required = Required.Always)]
 	public string Uuid { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public int Thing { get; set; }
 }
 
diff --git a/core/data/tests/can_handle_serde_rename/output.cs b/core/data/tests/can_handle_serde_rename/output.cs
index 4d6440d6..4385e58d 100644
--- a/core/data/tests/can_handle_serde_rename/output.cs
+++ b/core/data/tests/can_handle_serde_rename/output.cs
@@ -10,10 +10,14 @@ public class OtherType {
 
 /** This is a comment. */
 public class Person {
+	[JsonProperty(Required = Required.Always)]
 	public string name { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public ushort age { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public int extraSpecialFieldOne { get; set; }
 	public IEnumerable<string>? extraSpecialFieldTwo { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public OtherType nonStandardDataType { get; set; }
 	public IEnumerable<OtherType>? nonStandardDataTypeInArray { get; set; }
 }
diff --git a/core/data/tests/can_handle_serde_rename_all/output.cs b/core/data/tests/can_handle_serde_rename_all/output.cs
index 584912f7..1d67137d 100644
--- a/core/data/tests/can_handle_serde_rename_all/output.cs
+++ b/core/data/tests/can_handle_serde_rename_all/output.cs
@@ -7,17 +7,24 @@
 
 /** This is a Person struct with camelCase rename */
 public class Person {
+	[JsonProperty(Required = Required.Always)]
 	public string firstName { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public string lastName { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public ushort age { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public int extraSpecialField1 { get; set; }
 	public IEnumerable<string>? extraSpecialField2 { get; set; }
 }
 
 /** This is a Person2 struct with UPPERCASE rename */
 public class Person2 {
+	[JsonProperty(Required = Required.Always)]
 	public string FIRST_NAME { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public string LAST_NAME { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public ushort AGE { get; set; }
 }
 
diff --git a/core/data/tests/can_handle_serde_rename_on_top_level/output.cs b/core/data/tests/can_handle_serde_rename_on_top_level/output.cs
index 1043375d..0fc6b3e8 100644
--- a/core/data/tests/can_handle_serde_rename_on_top_level/output.cs
+++ b/core/data/tests/can_handle_serde_rename_on_top_level/output.cs
@@ -10,10 +10,14 @@ public class OtherType {
 
 /** This is a comment. */
 public class PersonTwo {
+	[JsonProperty(Required = Required.Always)]
 	public string name { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public ushort age { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public int extraSpecialFieldOne { get; set; }
 	public IEnumerable<string>? extraSpecialFieldTwo { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public OtherType nonStandardDataType { get; set; }
 	public IEnumerable<OtherType>? nonStandardDataTypeInArray { get; set; }
 }
diff --git a/core/data/tests/can_override_types/output.cs b/core/data/tests/can_override_types/output.cs
index 836a61ca..21c53789 100644
--- a/core/data/tests/can_override_types/output.cs
+++ b/core/data/tests/can_override_types/output.cs
@@ -6,11 +6,13 @@
 using System.Runtime.Serialization;
 
 public class OverrideStruct {
+	[JsonProperty(Required = Required.Always)]
 	public char fieldToOverride { get; set; }
 }
 
 /** Generated type representing the anonymous struct variant `AnonymousStructVariant` of the `OverrideEnum` Rust enum */
 public class OverrideEnumAnonymousStructVariantInner {
+	[JsonProperty(Required = Required.Always)]
 	public char fieldToOverride { get; set; }
 }
 
diff --git a/core/data/tests/can_recognize_types_inside_modules/output.cs b/core/data/tests/can_recognize_types_inside_modules/output.cs
index feacde35..e631b983 100644
--- a/core/data/tests/can_recognize_types_inside_modules/output.cs
+++ b/core/data/tests/can_recognize_types_inside_modules/output.cs
@@ -6,18 +6,22 @@
 using System.Runtime.Serialization;
 
 public class A {
+	[JsonProperty(Required = Required.Always)]
 	public uint Field { get; set; }
 }
 
 public class ABC {
+	[JsonProperty(Required = Required.Always)]
 	public uint Field { get; set; }
 }
 
 public class AB {
+	[JsonProperty(Required = Required.Always)]
 	public uint Field { get; set; }
 }
 
 public class OutsideOfModules {
+	[JsonProperty(Required = Required.Always)]
 	public uint Field { get; set; }
 }
 
diff --git a/core/data/tests/generate_types/output.cs b/core/data/tests/generate_types/output.cs
index 5c93be46..690fdefe 100644
--- a/core/data/tests/generate_types/output.cs
+++ b/core/data/tests/generate_types/output.cs
@@ -9,15 +9,24 @@ public class CustomType {
 }
 
 public class Types {
+	[JsonProperty(Required = Required.Always)]
 	public string S { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public string StaticS { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public short Int8 { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public float Float { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public double Double { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<string> Array { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public string[] FixedLengthArray { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public IDictionary<string, int> Dictionary { get; set; }
 	public IDictionary<string, int>? OptionalDictionary { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public CustomType CustomType { get; set; }
 }
 
diff --git a/core/data/tests/kebab_case_rename/output.cs b/core/data/tests/kebab_case_rename/output.cs
index b79628e0..2652b7c4 100644
--- a/core/data/tests/kebab_case_rename/output.cs
+++ b/core/data/tests/kebab_case_rename/output.cs
@@ -7,6 +7,7 @@
 
 /** This is a comment. */
 public class Things {
+	[JsonProperty(Required = Required.Always)]
 	public string bla { get; set; }
 	public string? label { get; set; }
 	public string? label-left { get; set; }
diff --git a/core/data/tests/recursive_enum_decorator/output.cs b/core/data/tests/recursive_enum_decorator/output.cs
index f309cdaf..a3e581e0 100644
--- a/core/data/tests/recursive_enum_decorator/output.cs
+++ b/core/data/tests/recursive_enum_decorator/output.cs
@@ -19,11 +19,13 @@ public record Vermont(Options Content) : Options();
 
 /** Generated type representing the anonymous struct variant `Exactly` of the `MoreOptions` Rust enum */
 public class MoreOptionsExactlyInner {
+	[JsonProperty(Required = Required.Always)]
 	public string Config { get; set; }
 }
 
 /** Generated type representing the anonymous struct variant `Built` of the `MoreOptions` Rust enum */
 public class MoreOptionsBuiltInner {
+	[JsonProperty(Required = Required.Always)]
 	public MoreOptions Top { get; set; }
 }
 
diff --git a/core/data/tests/resolves_qualified_type/output.cs b/core/data/tests/resolves_qualified_type/output.cs
index 1fb82657..ad1f9cd1 100644
--- a/core/data/tests/resolves_qualified_type/output.cs
+++ b/core/data/tests/resolves_qualified_type/output.cs
@@ -6,9 +6,13 @@
 using System.Runtime.Serialization;
 
 public class QualifiedTypes {
+	[JsonProperty(Required = Required.Always)]
 	public string Unqualified { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public string Qualified { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<string> QualifiedVec { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public IDictionary<string, string> QualifiedHashmap { get; set; }
 	public string? QualifiedOptional { get; set; }
 	public IDictionary<string, IEnumerable<string>>? QualfiedOptionalHashmapVec { get; set; }
diff --git a/core/data/tests/serialize_field_as/output.cs b/core/data/tests/serialize_field_as/output.cs
index 038a5506..048d0178 100644
--- a/core/data/tests/serialize_field_as/output.cs
+++ b/core/data/tests/serialize_field_as/output.cs
@@ -6,7 +6,9 @@
 using System.Runtime.Serialization;
 
 public class EditItemViewModelSaveRequest {
+	[JsonProperty(Required = Required.Always)]
 	public string Context { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<EditItemSaveValue> Values { get; set; }
 	public AutoFillItemActionRequest? FillAction { get; set; }
 }
diff --git a/core/data/tests/smart_pointers/output.cs b/core/data/tests/smart_pointers/output.cs
index b3e8470f..23e0a027 100644
--- a/core/data/tests/smart_pointers/output.cs
+++ b/core/data/tests/smart_pointers/output.cs
@@ -7,37 +7,49 @@
 
 /** This is a comment. */
 public class ArcyColors {
+	[JsonProperty(Required = Required.Always)]
 	public ushort Red { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public string Blue { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<string> Green { get; set; }
 }
 
 /** This is a comment. */
 public class MutexyColors {
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<string> Blue { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public string Green { get; set; }
 }
 
 /** This is a comment. */
 public class RcyColors {
+	[JsonProperty(Required = Required.Always)]
 	public string Red { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<string> Blue { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public string Green { get; set; }
 }
 
 /** This is a comment. */
 public class CellyColors {
+	[JsonProperty(Required = Required.Always)]
 	public string Red { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public IEnumerable<string> Blue { get; set; }
 }
 
 /** This is a comment. */
 public class LockyColors {
+	[JsonProperty(Required = Required.Always)]
 	public string Red { get; set; }
 }
 
 /** This is a comment. */
 public class CowyColors {
+	[JsonProperty(Required = Required.Always)]
 	public string Lifetime { get; set; }
 }
 
diff --git a/core/data/tests/test_generate_char/output.cs b/core/data/tests/test_generate_char/output.cs
index cb2c1677..83c000b1 100644
--- a/core/data/tests/test_generate_char/output.cs
+++ b/core/data/tests/test_generate_char/output.cs
@@ -6,6 +6,7 @@
 using System.Runtime.Serialization;
 
 public class MyType {
+	[JsonProperty(Required = Required.Always)]
 	public char Field { get; set; }
 }
 
diff --git a/core/data/tests/test_i54_u53_type/output.cs b/core/data/tests/test_i54_u53_type/output.cs
index de49db18..fd0defaa 100644
--- a/core/data/tests/test_i54_u53_type/output.cs
+++ b/core/data/tests/test_i54_u53_type/output.cs
@@ -6,7 +6,9 @@
 using System.Runtime.Serialization;
 
 public class Foo {
+	[JsonProperty(Required = Required.Always)]
 	public long A { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public ulong B { get; set; }
 }
 
diff --git a/core/data/tests/test_serde_iso8601/output.cs b/core/data/tests/test_serde_iso8601/output.cs
index 0a8c5123..5bbe3772 100644
--- a/core/data/tests/test_serde_iso8601/output.cs
+++ b/core/data/tests/test_serde_iso8601/output.cs
@@ -6,6 +6,7 @@
 using System.Runtime.Serialization;
 
 public class Foo {
+	[JsonProperty(Required = Required.Always)]
 	public string Time { get; set; }
 }
 
diff --git a/core/data/tests/test_serde_url/output.cs b/core/data/tests/test_serde_url/output.cs
index dde28904..4b1f3f64 100644
--- a/core/data/tests/test_serde_url/output.cs
+++ b/core/data/tests/test_serde_url/output.cs
@@ -6,6 +6,7 @@
 using System.Runtime.Serialization;
 
 public class Foo {
+	[JsonProperty(Required = Required.Always)]
 	public string Url { get; set; }
 }
 
diff --git a/core/data/tests/use_correct_integer_types/output.cs b/core/data/tests/use_correct_integer_types/output.cs
index 3ba7c226..eb0690b6 100644
--- a/core/data/tests/use_correct_integer_types/output.cs
+++ b/core/data/tests/use_correct_integer_types/output.cs
@@ -7,11 +7,17 @@
 
 /** This is a comment. */
 public class Foo {
+	[JsonProperty(Required = Required.Always)]
 	public short A { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public short B { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public int C { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public ushort E { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public ushort F { get; set; }
+	[JsonProperty(Required = Required.Always)]
 	public uint G { get; set; }
 }
 
diff --git a/core/tests/snapshot_tests.rs b/core/tests/snapshot_tests.rs
index b08fbc0a..360fd3a1 100644
--- a/core/tests/snapshot_tests.rs
+++ b/core/tests/snapshot_tests.rs
@@ -642,7 +642,7 @@ tests! {
     const_enum_decorator: [ swift{ prefix: "OP".to_string(), } ];
     algebraic_enum_decorator: [ swift{ prefix: "OP".to_string(), } ];
     struct_decorator: [ kotlin, swift{ prefix: "OP".to_string(), } ];
-    serialize_field_as: [kotlin, swift, typescript, scala,  go];
+    serialize_field_as: [kotlin, swift, typescript, scala,  go, csharp];
     serialize_type_alias: [kotlin, swift, typescript, scala,  go];
     serialize_anonymous_field_as: [kotlin, swift, typescript, scala,  go, csharp];
     smart_pointers: [kotlin, swift, typescript, scala, go, csharp];