Use keyword examples instead of example

Author: irvinesunday

src/Microsoft.OpenApi/Validations/Rules/JsonSchemaRules.cs

@@ -34,12 +34,18 @@ public static class JsonSchemaRules
 
                     context.Exit();
 
-                    // example
-                    context.Enter("example");
+                    // examples
+                    context.Enter("examples");
 
-                    if (jsonSchema.GetExample() != null)
+                    if (jsonSchema.GetExamples() != null)
                     {
-                        RuleHelpers.ValidateDataTypeMismatch(context, nameof(SchemaMismatchedDataType), jsonSchema.GetExample(), jsonSchema);
+                        for (int i = 0; i < jsonSchema.GetExamples().Count(); i++)
+                        {
+                            context.Enter(i.ToString());
+                            RuleHelpers.ValidateDataTypeMismatch(context, nameof(SchemaMismatchedDataType), jsonSchema.GetExamples().ElementAt(i), jsonSchema);
+                            context.Exit();
+                        }
+                        
                     }
 
                     context.Exit();

src/Microsoft.OpenApi/Writers/OpenApiWriterBase.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
 using System;
@@ -574,9 +574,9 @@ public void WriteJsonSchemaWithoutReference(IOpenApiWriter writer, JsonSchema sc
 
             // externalDocs
             writer.WriteOptionalObject(OpenApiConstants.ExternalDocs, schema.GetExternalDocs(), (w, s) => JsonSerializer.Serialize(s));
-
-            // example
-            writer.WriteOptionalObject(OpenApiConstants.Example, schema.GetExample(), (w, e) => w.WriteAny(new OpenApiAny(e)));
+            
+            // examples
+            writer.WriteOptionalCollection(OpenApiConstants.Examples, schema.GetExamples(), (n, e) => n.WriteAny(new OpenApiAny(e)));
 
             // deprecated
             writer.WriteProperty(OpenApiConstants.Deprecated, schema.GetDeprecated(), false);

test/Microsoft.OpenApi.Readers.Tests/V31Tests/Samples/OpenApiDocument/docWithExample.yaml

@@ -61,7 +61,8 @@ paths: # The available paths and operations for the API
                 properties:
                   message: # A property for the confirmation message
                     type: string
-                    example: File uploaded successfully
+                    examples:
+                      - The file was uploaded successfully
 components: # Reusable components for the API
   schemas: # JSON Schema definitions for the API
     User: # A schema for a user object