diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpClientCodegen.java
index f69ffd9237f..cab9ee837fe 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpClientCodegen.java
@@ -536,33 +536,6 @@ public class CSharpClientCodegen extends AbstractCSharpCodegen {
         return this.modelPropertyNaming;
     }
 
-    @Override
-    public Map<String, Object> postProcessOperationsWithModels(Map<String, Object> objs, List<Object> allModels) {
-        super.postProcessOperationsWithModels(objs, allModels);
-        if (objs != null) {
-            Map<String, Object> operations = (Map<String, Object>) objs.get("operations");
-            if (operations != null) {
-                List<CodegenOperation> ops = (List<CodegenOperation>) operations.get("operation");
-                for (CodegenOperation operation : ops) {
-                    if (operation.returnType != null) {
-                        operation.returnContainer = operation.returnType;
-                        if (this.returnICollection && (
-                                operation.returnType.startsWith("List") ||
-                                        operation.returnType.startsWith("Collection"))) {
-                            // NOTE: ICollection works for both List<T> and Collection<T>
-                            int genericStart = operation.returnType.indexOf("<");
-                            if (genericStart > 0) {
-                                operation.returnType = "ICollection" + operation.returnType.substring(genericStart);
-                            }
-                        }
-                    }
-                }
-            }
-        }
-
-        return objs;
-    }
-
     @Override
     public CodegenType getTag() {
         return CodegenType.CLIENT;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpNetCoreClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpNetCoreClientCodegen.java
index 2e0a3bd1223..96c7c92f5ec 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpNetCoreClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpNetCoreClientCodegen.java
@@ -468,33 +468,6 @@ public class CSharpNetCoreClientCodegen extends AbstractCSharpCodegen {
         super.postProcessModelProperty(model, property);
     }
 
-    @Override
-    public Map<String, Object> postProcessOperationsWithModels(Map<String, Object> objs, List<Object> allModels) {
-        super.postProcessOperationsWithModels(objs, allModels);
-        if (objs != null) {
-            Map<String, Object> operations = (Map<String, Object>) objs.get("operations");
-            if (operations != null) {
-                List<CodegenOperation> ops = (List<CodegenOperation>) operations.get("operation");
-                for (CodegenOperation operation : ops) {
-                    if (operation.returnType != null) {
-                        operation.returnContainer = operation.returnType;
-                        if (this.returnICollection && (
-                                operation.returnType.startsWith("List") ||
-                                        operation.returnType.startsWith("Collection"))) {
-                            // NOTE: ICollection works for both List<T> and Collection<T>
-                            int genericStart = operation.returnType.indexOf("<");
-                            if (genericStart > 0) {
-                                operation.returnType = "ICollection" + operation.returnType.substring(genericStart);
-                            }
-                        }
-                    }
-                }
-            }
-        }
-
-        return objs;
-    }
-
     @Override
     public void postProcessParameter(CodegenParameter parameter) {
         postProcessPattern(parameter.pattern, parameter.vendorExtensions);