1 files changed, 37 insertions, 0 deletions
diff --git a/release-notes/7.0/preview/api-diff/preview7/Microsoft.NETCore.App/7.0-preview7_System.Text.Json.Serialization.md b/release-notes/7.0/preview/api-diff/preview7/Microsoft.NETCore.App/7.0-preview7_System.Text.Json.Serialization.md
new file mode 100644
index 00000000..76568e54
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+++ b/release-notes/7.0/preview/api-diff/preview7/Microsoft.NETCore.App/7.0-preview7_System.Text.Json.Serialization.md
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+# System.Text.Json.Serialization
+
+``` diff
+ namespace System.Text.Json.Serialization {
+-    [NullableAttribute((byte)0)]
+-    [NullableContextAttribute((byte)1)]
+-    public class JsonPolymorphicTypeConfiguration : ICollection<(Type, object?)>, IEnumerable, IEnumerable<(Type, object?)> {
+-        public JsonPolymorphicTypeConfiguration(Type baseType);
+-        public Type BaseType { get; }
+-        public bool IgnoreUnrecognizedTypeDiscriminators { get; set; }
+-        int ICollection<(Type, object?)>.Count { get; }
+-        bool ICollection<(Type, object?)>.IsReadOnly { get; }
+-        [NullableAttribute((byte)2)]
+-        public string? TypeDiscriminatorPropertyName { [NullableContextAttribute((byte)2)] get; [NullableContextAttribute((byte)2)] set; }
+-        public JsonUnknownDerivedTypeHandling UnknownDerivedTypeHandling { get; set; }
+-        void ICollection<(Type, object?)>.Add((Type DerivedType, object TypeDiscriminator) item);
+-        void ICollection<(Type, object?)>.Clear();
+-        bool ICollection<(Type, object?)>.Contains((Type DerivedType, object TypeDiscriminator) item);
+-        void ICollection<(Type, object?)>.CopyTo((Type DerivedType, object TypeDiscriminator)[] array, int arrayIndex);
+-        bool ICollection<(Type, object?)>.Remove((Type DerivedType, object TypeDiscriminator) item);
+-        IEnumerator<(Type DerivedType, object TypeDiscriminator)> IEnumerable<(Type, object?)>.GetEnumerator();
+-        IEnumerator IEnumerable.GetEnumerator();
+-        public JsonPolymorphicTypeConfiguration WithDerivedType(Type derivedType);
+-        public JsonPolymorphicTypeConfiguration WithDerivedType(Type derivedType, int typeDiscriminator);
+-        public JsonPolymorphicTypeConfiguration WithDerivedType(Type derivedType, string typeDiscriminator);
+-    }
+-    [NullableAttribute((byte)0)]
+-    [NullableContextAttribute((byte)1)]
+-    public class JsonPolymorphicTypeConfiguration<TBaseType> : JsonPolymorphicTypeConfiguration where TBaseType : class {
+-        public JsonPolymorphicTypeConfiguration();
+-        public JsonPolymorphicTypeConfiguration<TBaseType> WithDerivedType<TDerivedType>() where TDerivedType : TBaseType;
+-        public JsonPolymorphicTypeConfiguration<TBaseType> WithDerivedType<TDerivedType>(int typeDiscriminator) where TDerivedType : TBaseType;
+-        public JsonPolymorphicTypeConfiguration<TBaseType> WithDerivedType<TDerivedType>(string typeDiscriminator) where TDerivedType : TBaseType;
+-    }
+ }
+```
+