Marking a class abstract should not mark the methods abstract as well

bin/configs/aspnetcore-8.0-abstract-class.yaml

@@ -0,0 +1,9 @@
+generatorName: aspnetcore
+outputDir: samples/server/petstore/aspnetcore-8.0-abstract-class
+inputSpec: modules/openapi-generator/src/test/resources/3_0/aspnetcore/petstore.yaml
+templateDir: modules/openapi-generator/src/main/resources/aspnetcore/3.0
+additionalProperties:
+  packageGuid: '{3C799344-F285-4669-8FD5-7ED9B795D5C5}'
+  aspnetCoreVersion: "8.0"
+  userSecretsGuid: 'cb87e868-8646-48ef-9bb6-344b537d0d37'
+  classModifier: abstract

bin/configs/csharp-functions-abstract-class.yaml

@@ -0,0 +1,6 @@
+generatorName: csharp-functions
+outputDir: samples/server/petstore/csharp-functions-abstract-class
+inputSpec: modules/openapi-generator/src/test/resources/3_0/petstore.yaml
+templateDir: modules/openapi-generator/src/main/resources/csharp-functions
+additionalProperties:
+  classModifier: abstract

bin/configs/csharp-functions-latest.yaml

@@ -1,5 +1,5 @@
 generatorName: csharp-functions
-outputDir: samples/client/petstore/csharp-functions
+outputDir: samples/server/petstore/csharp-functions
 inputSpec: modules/openapi-generator/src/test/resources/3_0/petstore.yaml
 templateDir: modules/openapi-generator/src/main/resources/csharp-functions
 additionalProperties:

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AspNetServerCodegen.java

@@ -673,15 +673,8 @@ private void setCliOption(CliOption cliOption) throws IllegalArgumentException {
     }
 
     private void setClassModifier() {
-        // CHeck for class modifier if not present set the default value.
+        // Check for class modifier if not present set the default value.
         setCliOption(classModifier);
-
-        // If class modifier is abstract then the methods need to be abstract too.
-        if ("abstract".equals(classModifier.getOptValue())) {
-            operationModifier.setOptValue(classModifier.getOptValue());
-            additionalProperties.put(OPERATION_MODIFIER, operationModifier.getOptValue());
-            LOGGER.warn("classModifier is {} so forcing operationModifier to {}", classModifier.getOptValue(), operationModifier.getOptValue());
-        }
     }
 
     private void setOperationModifier() {

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpFunctionsServerCodegen.java

@@ -539,15 +539,8 @@ private void setCliOption(CliOption cliOption) throws IllegalArgumentException {
     }
 
     private void setClassModifier() {
-        // CHeck for class modifier if not present set the default value.
+        // Check for class modifier if not present set the default value.
         setCliOption(classModifier);
-
-        // If class modifier is abstract then the methods need to be abstract too.
-        if ("abstract".equals(classModifier.getOptValue())) {
-            operationModifier.setOptValue(classModifier.getOptValue());
-            additionalProperties.put(OPERATION_MODIFIER, operationModifier.getOptValue());
-            LOGGER.warn("classModifier is {} so forcing operationModifier to {}", classModifier.getOptValue(), operationModifier.getOptValue());
-        }
     }
 
     private void setOperationModifier() {

modules/openapi-generator/src/test/java/org/openapitools/codegen/csharpnetcore/AspNetServerCodegenTest.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2026 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.openapitools.codegen.csharpnetcore;
+
+import org.openapitools.codegen.languages.AspNetServerCodegen;
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+public class AspNetServerCodegenTest {
+
+    @Test
+    public void abstractClassUsesDefaultVirtualOperations() {
+        final AspNetServerCodegen codegen = new AspNetServerCodegen();
+        codegen.additionalProperties().put("classModifier", "abstract");
+
+        codegen.processOpts();
+
+        Assert.assertEquals(codegen.additionalProperties().get("classModifier"), "abstract");
+        Assert.assertEquals(codegen.additionalProperties().get("operationModifier"), "virtual");
+        Assert.assertEquals(codegen.additionalProperties().get("generateBody"), Boolean.TRUE);
+    }
+
+    @Test
+    public void abstractOperationsDisableBodyGeneration() {
+        final AspNetServerCodegen codegen = new AspNetServerCodegen();
+        codegen.additionalProperties().put("classModifier", "abstract");
+        codegen.additionalProperties().put("operationModifier", "abstract");
+
+        codegen.processOpts();
+
+        Assert.assertEquals(codegen.additionalProperties().get("operationModifier"), "abstract");
+        Assert.assertEquals(codegen.additionalProperties().get("generateBody"), Boolean.FALSE);
+    }
+
+    @Test
+    public void libraryBuildUsesDefaultVirtualOperations() {
+        final AspNetServerCodegen codegen = new AspNetServerCodegen();
+        codegen.additionalProperties().put("buildTarget", "library");
+
+        codegen.processOpts();
+
+        Assert.assertEquals(codegen.additionalProperties().get("classModifier"), "abstract");
+        Assert.assertEquals(codegen.additionalProperties().get("operationModifier"), "virtual");
+        Assert.assertEquals(codegen.additionalProperties().get("generateBody"), Boolean.TRUE);
+    }
+}

modules/openapi-generator/src/test/java/org/openapitools/codegen/csharpnetcorefunctions/CSharpFunctionsServerCodegenTest.java

@@ -37,4 +37,39 @@ public void testToEnumVarName() throws Exception {
         // Assert.assertEquals(codegen.toEnumVarName("FOO-BAR", "string"), "FooBar");
         // Assert.assertEquals(codegen.toEnumVarName("FOO_BAR", "string"), "FooBar");
     }
+
+    @Test
+    public void abstractClassUsesDefaultVirtualOperations() {
+        final CSharpFunctionsServerCodegen codegen = new CSharpFunctionsServerCodegen();
+        codegen.additionalProperties().put("classModifier", "abstract");
+
+        codegen.processOpts();
+
+        Assert.assertEquals(codegen.additionalProperties().get("classModifier"), "abstract");
+        Assert.assertEquals(codegen.additionalProperties().get("operationModifier"), "virtual");
+        Assert.assertEquals(codegen.additionalProperties().get("generateBody"), Boolean.TRUE);
+    }
+
+    @Test
+    public void abstractOperationsDisableBodyGeneration() {
+        final CSharpFunctionsServerCodegen codegen = new CSharpFunctionsServerCodegen();
+        codegen.additionalProperties().put("classModifier", "abstract");
+        codegen.additionalProperties().put("operationModifier", "abstract");
+
+        codegen.processOpts();
+
+        Assert.assertEquals(codegen.additionalProperties().get("operationModifier"), "abstract");
+        Assert.assertEquals(codegen.additionalProperties().get("generateBody"), Boolean.FALSE);
+    }
+
+    @Test
+    public void libraryBuildUsesDefaultVirtualOperations() {
+        final CSharpFunctionsServerCodegen codegen = new CSharpFunctionsServerCodegen();
+        codegen.additionalProperties().put("buildTarget", "library");
+
+        codegen.processOpts();
+
+        Assert.assertEquals(codegen.additionalProperties().get("operationModifier"), "virtual");
+        Assert.assertEquals(codegen.additionalProperties().get("generateBody"), Boolean.TRUE);
+    }
 }