write the binary to base64string and read it as byte[]

Author: xuzhg

src/Microsoft.OpenApi.Readers/ParseNodes/OpenApiAnyConverter.cs

@@ -195,13 +195,17 @@ public static IOpenApiAny GetSpecificOpenApiAny(IOpenApiAny openApiAny, OpenApiS
 
             if (type == "string" && format == "byte")
             {
-                if ( byte.TryParse(value, NumberStyles.Any, CultureInfo.InvariantCulture, out var byteValue))
+                if (byte.TryParse(value, NumberStyles.Any, CultureInfo.InvariantCulture, out var byteValue))
                 {
                     return new OpenApiByte(byteValue);
                 }
             }
 
-            // TODO: Parse byte array to OpenApiBinary type.
+            // binary
+            if (type == "string" && format == "binary")
+            {
+                return new OpenApiBinary(Convert.FromBase64String(value));
+            }
 
             if (type == "string" && format == "date")
             {

src/Microsoft.OpenApi/Writers/OpenApiWriterAnyExtensions.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license. 
 
+using System;
 using System.Collections.Generic;
 using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Exceptions;
@@ -170,7 +171,14 @@ private static void WritePrimitive(this IOpenApiWriter writer, IOpenApiPrimitive
 
                 case PrimitiveType.Binary:
                     var binaryValue = (OpenApiBinary)primitive;
-                    writer.WriteValue(binaryValue.Value);
+                    if (binaryValue == null)
+                    {
+                        writer.WriteNull();
+                    }
+                    else
+                    {
+                        writer.WriteValue(Convert.ToBase64String(binaryValue.Value));
+                    }
                     break;
 
                 case PrimitiveType.Boolean:

test/Microsoft.OpenApi.Tests/Models/OpenApiExampleTests.cs

@@ -30,7 +30,8 @@ public class OpenApiExampleTests
                             new OpenApiObject
                             {
                                 ["href"] = new OpenApiString("http://example.com/1"),
-                                ["rel"] = new OpenApiString("sampleRel1")
+                                ["rel"] = new OpenApiString("sampleRel1"),
+                                ["binary"] = new OpenApiBinary(new byte[] { 1, 2, 3 })
                             }
                         }
                     },
@@ -117,7 +118,8 @@ public void SerializeAdvancedExampleAsV3JsonWorks()
         ""links"": [
           {
             ""href"": ""http://example.com/1"",
-            ""rel"": ""sampleRel1""
+            ""rel"": ""sampleRel1"",
+            ""binary"": ""AQID""
           }
         ]
       },