fixed empty diamond operator on aspnetcore

Author: HugoMario

src/main/java/io/swagger/codegen/v3/generators/dotnet/DotNetSchemaHandler.java

@@ -0,0 +1,26 @@
+package io.swagger.codegen.v3.generators.dotnet;
+
+import io.swagger.codegen.v3.CodegenModel;
+import io.swagger.codegen.v3.generators.DefaultCodegenConfig;
+import io.swagger.codegen.v3.generators.SchemaHandler;
+import io.swagger.v3.oas.models.media.ArraySchema;
+
+import java.util.Map;
+
+public class DotNetSchemaHandler extends SchemaHandler {
+
+    public DotNetSchemaHandler(DefaultCodegenConfig codegenConfig) {
+        super(codegenConfig);
+    }
+
+    protected CodegenModel processArrayItemSchema(CodegenModel codegenModel, ArraySchema arraySchema, Map<String, CodegenModel> allModels) {
+        final CodegenModel composedModel = super.processArrayItemSchema(codegenModel, arraySchema, allModels);
+        if (composedModel == null) {
+            return null;
+        }
+        if (codegenModel.getParent().equals("List<>")) {
+            codegenModel.setParent("List<" + composedModel.getClassname() + ">");
+        }
+        return composedModel;
+    }
+}

src/test/java/io/swagger/codegen/v3/generators/dotnet/AspNetCoreServerCodegenTest.java

@@ -0,0 +1,21 @@
+package io.swagger.codegen.v3.generators.dotnet;
+
+import io.swagger.codegen.v3.CodegenConfig;
+import io.swagger.codegen.v3.CodegenModel;
+import io.swagger.codegen.v3.generators.AbstractCodegenTest;
+import io.swagger.codegen.v3.generators.CodegenWrapper;
+import io.swagger.v3.oas.models.OpenAPI;
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+public class AspNetCoreServerCodegenTest extends AbstractCodegenTest {
+
+    @Test(description = "Verify if List<> is fixed for array schema with composed items.")
+    public void checkArrayItemsSchemaParent() {
+        final OpenAPI openAPI = getOpenAPI("3_0_0/composed_schemas.yaml");
+        final CodegenConfig config = new AspNetCoreServerCodegen();
+        final CodegenWrapper codegenWrapper = processSchemas(config, openAPI);
+        CodegenModel codegenModel = codegenWrapper.getAllModels().get("AllPetsResponse");
+        Assert.assertEquals(codegenModel.parent, "List<OneOfAllPetsResponseItems>");
+    }
+}