Use pattern matching and the native count extension method

Author: MaggieKimani1

src/Microsoft.OpenApi/Services/OpenApiReferenceResolver.cs

@@ -206,9 +206,12 @@ public override void Visit(ref JsonSchema schema)
             }
 
             var builder = new JsonSchemaBuilder();
-            foreach (var keyword in schema?.Keywords)
+            if (schema?.Keywords is { } keywords)
             {
-                builder.Add(keyword);
+                foreach (var keyword in schema?.Keywords)
+                {
+                    builder.Add(keyword);
+                }
             }
 
             ResolveJsonSchema(schema.GetItems(), r => builder.Items(r));

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

@@ -39,14 +39,12 @@ public static class JsonSchemaRules
 
                     if (jsonSchema.GetExamples() is { } examples)
                     {
-                        var examplesCount = examples.Count();
-                        for (int i = 0; i < examplesCount; i++)
+                        for (int i = 0; i < examples.Count; i++)
                         {
                             context.Enter(i.ToString());
                             RuleHelpers.ValidateDataTypeMismatch(context, nameof(SchemaMismatchedDataType), examples.ElementAt(i), jsonSchema);
                             context.Exit();
                         }
-                        
                     }
 
                     context.Exit();