Use schema from ISpecificRecord instead of reflecting a field (#1961)

* Use schema from ISpecificRecord instead of reflecting a field

* Use writer type for serialisation

* Added a line to CHANGELOG.md

* Update CHANGELOG

---------

Co-authored-by: Anchit Jain <[email protected]>

Author: AlexeyRaga

CHANGELOG.md

@@ -3,6 +3,7 @@
 - Added SetSaslCredentials. This new method (on the Producer, Consumer, and AdminClient) allows modifying the stored
   SASL PLAIN/SCRAM credentials that will be used for subsequent (new) connections to a broker (#1980).
 - Fixed `OverflowException` thrown intermittently when using the `ListGroup` method (#2003).
+- Changed the way the `_SCHEMA` filed is accessed internally from reflecting the static field to accessing it from the instance ([AlexeyRaga](https://github.com/AlexeyRaga)).
 
 
 # 2.0.2

src/Confluent.SchemaRegistry.Serdes.Avro/SpecificDeserializerImpl.cs

@@ -53,7 +53,7 @@ public SpecificDeserializerImpl(ISchemaRegistryClient schemaRegistryClient)
 
             if (typeof(ISpecificRecord).IsAssignableFrom(typeof(T)))
             {
-                ReaderSchema = (global::Avro.Schema)typeof(T).GetField("_SCHEMA", BindingFlags.Public | BindingFlags.Static).GetValue(null);
+                ReaderSchema = ((ISpecificRecord)Activator.CreateInstance<T>()).Schema;
             }
             else if (typeof(T).Equals(typeof(int)))
             {

src/Confluent.SchemaRegistry.Serdes.Avro/SpecificSerializerImpl.cs

@@ -123,7 +123,7 @@ private static SerializerSchemaData ExtractSchemaData(Type writerType)
             SerializerSchemaData serializerSchemaData = new SerializerSchemaData();
             if (typeof(ISpecificRecord).IsAssignableFrom(writerType))
             {
-                serializerSchemaData.WriterSchema = (global::Avro.Schema) writerType.GetField("_SCHEMA", BindingFlags.Public | BindingFlags.Static).GetValue(null);
+                serializerSchemaData.WriterSchema = ((ISpecificRecord)Activator.CreateInstance(writerType)).Schema;
             }
             else if (writerType.Equals(typeof(int)))
             {