Fix/issue 176 enum properties

src/MicroElements.Swashbuckle.FluentValidation/OpenApi/OpenApiSchemaCompatibility.cs

@@ -452,7 +452,10 @@ public static IEnumerable<KeyValuePair<string, OpenApiSchema>> GetProperties(Ope
 #if OPENAPI_V2
             if (schema.Properties == null)
                 return Enumerable.Empty<KeyValuePair<string, OpenApiSchema>>();
+            // Filter out OpenApiSchemaReference entries (e.g., enum types) to avoid InvalidCastException
+            // Issue #176: https://github.com/micro-elements/MicroElements.Swashbuckle.FluentValidation/issues/176
             return schema.Properties
+                .Where(kvp => kvp.Value is OpenApiSchema)
                 .Select(kvp => new KeyValuePair<string, OpenApiSchema>(kvp.Key, (OpenApiSchema)kvp.Value));
 #else
             return schema.Properties ?? Enumerable.Empty<KeyValuePair<string, OpenApiSchema>>();

test/MicroElements.Swashbuckle.FluentValidation.Tests/SchemaGenerationTests.EnumProperties.cs

@@ -0,0 +1,80 @@
+// Copyright (c) MicroElements. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using FluentAssertions;
+using FluentValidation;
+#if OPENAPI_V2
+using Microsoft.OpenApi;
+#else
+using Microsoft.OpenApi.Models;
+#endif
+using Swashbuckle.AspNetCore.SwaggerGen;
+using Xunit;
+
+namespace MicroElements.Swashbuckle.FluentValidation.Tests
+{
+    /// <summary>
+    /// Tests for models with enum properties.
+    /// Issue #176: https://github.com/micro-elements/MicroElements.Swashbuckle.FluentValidation/issues/176
+    /// </summary>
+    public partial class SchemaGenerationTests
+    {
+        public enum SampleStatus
+        {
+            Pending,
+            Active,
+            Completed
+        }
+
+        public class ModelWithEnumProperty
+        {
+            public string Name { get; set; } = string.Empty;
+            public SampleStatus Status { get; set; }
+            public string Description { get; set; } = string.Empty;
+        }
+
+        public class ModelWithEnumPropertyValidator : AbstractValidator<ModelWithEnumProperty>
+        {
+            public ModelWithEnumPropertyValidator()
+            {
+                RuleFor(x => x.Name).NotEmpty().MaximumLength(100);
+                RuleFor(x => x.Description).MaximumLength(500);
+            }
+        }
+
+        /// <summary>
+        /// Issue #176: InvalidCastException when models contain enum properties.
+        /// In OpenAPI v2 (Microsoft.OpenApi 2.x), enum properties are represented as OpenApiSchemaReference,
+        /// not OpenApiSchema, causing InvalidCastException in GetProperties method.
+        /// </summary>
+        [Fact]
+        public void Model_With_Enum_Property_Should_Not_Throw_InvalidCastException()
+        {
+            // Arrange
+            var schemaRepository = new SchemaRepository();
+
+            // Act - This should not throw InvalidCastException
+            var referenceSchema = SchemaGenerator(new ModelWithEnumPropertyValidator())
+                .GenerateSchema(typeof(ModelWithEnumProperty), schemaRepository);
+
+            // Assert
+            var schema = schemaRepository.GetSchema(referenceSchema.GetRefId()!);
+
+            // Non-enum properties should have validation rules applied (using PascalCase as in C# property names)
+            var nameProperty = schema.GetProperty("Name");
+            nameProperty.Should().NotBeNull("Name property should exist in schema");
+            nameProperty!.MinLength.Should().Be(1);
+            nameProperty.MaxLength.Should().Be(100);
+
+            var descriptionProperty = schema.GetProperty("Description");
+            descriptionProperty.Should().NotBeNull("Description property should exist in schema");
+            descriptionProperty!.MaxLength.Should().Be(500);
+
+            // Schema should have all properties (including enum)
+            schema.Properties.Should().HaveCount(3);
+            schema.Properties.Keys.Should().Contain("Name");
+            schema.Properties.Keys.Should().Contain("Status");
+            schema.Properties.Keys.Should().Contain("Description");
+        }
+    }
+}

version.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <VersionPrefix>7.0.1</VersionPrefix>
+    <VersionPrefix>7.0.2</VersionPrefix>
     <VersionSuffix></VersionSuffix>
   </PropertyGroup>
 </Project>