diff --git a/packages/http-client-csharp/emitter/src/emitter.ts b/packages/http-client-csharp/emitter/src/emitter.ts
index 5181521c8c..a60cae1774 100644
--- a/packages/http-client-csharp/emitter/src/emitter.ts
+++ b/packages/http-client-csharp/emitter/src/emitter.ts
@@ -1,7 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License. See License.txt in the project root for license information.
 
-import { createSdkContext, UsageFlags } from "@azure-tools/typespec-client-generator-core";
+import { createSdkContext, SdkClientType, SdkHttpOperation, SdkServiceMethod, UsageFlags } from "@azure-tools/typespec-client-generator-core";
 import {
   EmitContext,
   getDirectoryPath,
@@ -23,6 +23,9 @@ import { Logger } from "./lib/logger.js";
 import { NetEmitterOptions, resolveOptions, resolveOutputFolder } from "./options.js";
 import { defaultSDKContextOptions } from "./sdk-context-options.js";
 import { Configuration } from "./type/configuration.js";
+import { CodeModel } from "./type/code-model.js";
+import { InputClient } from "./type/input-client.js";
+import { InputOperation } from "./type/input-operation.js";
 
 /**
  * Look for the project root by looking up until a `package.json` is found.
@@ -44,7 +47,75 @@ function findProjectRoot(path: string): string | undefined {
   }
 }
 
-export async function $onEmit(context: EmitContext<NetEmitterOptions>) {
+/** Start: all these in azure emitter */
+interface AzureCodeModel extends CodeModel {
+  AzureStuff: string;
+}
+
+interface AzureInputClient extends InputClient {
+  AzureStuff: string;
+}
+
+interface AzureInputOperation extends InputOperation {
+  AzureStuff: string;
+}
+
+interface ResoureceMetadata {
+  models?: {
+    operations: string[]
+  }
+}
+
+type AzureModelType = {
+  client: AzureInputClient;
+  operation: AzureInputOperation;
+  resources: ResoureceMetadata;
+}
+
+const azureHook: Hook<AzureModelType> = {
+  emitClient: (client: SdkClientType<SdkHttpOperation>, unbrandingClient: InputClient) => {
+    // Get something from TCGC client raw.
+    const azureStuff = "hello azure";
+    return {
+      ...unbrandingClient,
+      AzureStuff: azureStuff
+    };
+  },
+  emitOperation: (method: SdkServiceMethod<SdkHttpOperation>, unbrandingOperation: InputOperation) => {
+    // Get something from TCGC operation raw.
+    const azureStuff = "hello azure";
+    return {
+      ...unbrandingOperation,
+      AzureStuff: azureStuff
+    };
+  },
+  emitResources: () => {
+    // Get data from arm
+    return { "models": { "operations": []} };
+  }
+}
+
+export async function $onEmitInAzureEmitter(context: EmitContext<NetEmitterOptions>) {
+  $onEmit<AzureModelType>({
+    ...context,
+    "hook": azureHook
+  });
+}
+/** End: all these in azure emitter */
+
+
+export type CodeModelType = Record<"client"| "operation" | "resources", any>; // I think "resources" should be renamed to something like "others", just telling unbranding emitter just append these data.
+
+export interface Hook<T extends CodeModelType> {
+  emitClient?: (client: SdkClientType<SdkHttpOperation>, unbrandingClient: InputClient) => T["client"];
+  emitOperation?: (method: SdkServiceMethod<SdkHttpOperation>, unbrandingOperation: InputOperation) => T["operation"];
+  emitResources?: () => T["resources"];
+}
+
+export type ContextType<T extends CodeModelType> = EmitContext<NetEmitterOptions> & {"hook"?: Hook<T>};
+
+export async function $onEmit<T extends CodeModelType>(context: ContextType<T>) {
+  context.hook = azureHook as Hook<T>; // Ignore this line. Test purpose
   const program: Program = context.program;
   const options = resolveOptions(context);
   const outputFolder = resolveOutputFolder(context);
@@ -59,7 +130,7 @@ export async function $onEmit(context: EmitContext<NetEmitterOptions>) {
       "@typespec/http-client-csharp",
       defaultSDKContextOptions,
     );
-    const root = createModel(sdkContext);
+    const root = createModel<T>(sdkContext, context.hook); // context.hook is already in sdkContext. We should change createSdkContext signature to somehow accept hook type
     if (
       context.program.diagnostics.length > 0 &&
       context.program.diagnostics.filter((digs) => digs.severity === "error").length > 0
diff --git a/packages/http-client-csharp/emitter/src/lib/client-model-builder.ts b/packages/http-client-csharp/emitter/src/lib/client-model-builder.ts
index 880631124a..787826a144 100644
--- a/packages/http-client-csharp/emitter/src/lib/client-model-builder.ts
+++ b/packages/http-client-csharp/emitter/src/lib/client-model-builder.ts
@@ -25,8 +25,9 @@ import { Logger } from "./logger.js";
 import { navigateModels } from "./model.js";
 import { fromSdkServiceMethod, getParameterDefaultValue } from "./operation-converter.js";
 import { processServiceAuthentication } from "./service-authentication.js";
+import { CodeModelType, Hook } from "../emitter.js";
 
-export function createModel(sdkContext: SdkContext<NetEmitterOptions>): CodeModel {
+export function createModel<T extends CodeModelType>(sdkContext: SdkContext<NetEmitterOptions>, hook?: Hook<T>): CodeModel {
   const sdkPackage = sdkContext.sdkPackage;
 
   const sdkTypeMap: SdkTypeMap = {
@@ -49,6 +50,7 @@ export function createModel(sdkContext: SdkContext<NetEmitterOptions>): CodeMode
     sdkPackage.clients.filter((c) => c.initialization.access === "public"),
     inputClients,
     [],
+    hook
   );
 
   const clientModel: CodeModel = {
@@ -61,30 +63,31 @@ export function createModel(sdkContext: SdkContext<NetEmitterOptions>): CodeMode
   };
   return clientModel;
 
-  function fromSdkClients(
+  function fromSdkClients<T extends CodeModelType>(
     clients: SdkClientType<SdkHttpOperation>[],
     inputClients: InputClient[],
     parentClientNames: string[],
+    hook?: Hook<T>
   ) {
     for (const client of clients) {
-      const inputClient = emitClient(client, parentClientNames);
+      const inputClient = emitClient(client, parentClientNames, hook);
       inputClients.push(inputClient);
       const subClients = client.methods
         .filter((m) => m.kind === "clientaccessor")
         .map((m) => m.response as SdkClientType<SdkHttpOperation>);
       parentClientNames.push(inputClient.Name);
-      fromSdkClients(subClients, inputClients, parentClientNames);
+      fromSdkClients(subClients, inputClients, parentClientNames, hook);
       parentClientNames.pop();
     }
   }
 
-  function emitClient(client: SdkClientType<SdkHttpOperation>, parentNames: string[]): InputClient {
+  function emitClient<T extends CodeModelType>(client: SdkClientType<SdkHttpOperation>, parentNames: string[], hook?: Hook<T>): InputClient {
     const endpointParameter = client.initialization.properties.find(
       (p) => p.kind === "endpoint",
     ) as SdkEndpointParameter;
     const uri = getMethodUri(endpointParameter);
     const clientParameters = fromSdkEndpointParameter(endpointParameter);
-    return {
+    const unbrandingClient =  {
       Name: getClientName(client, parentNames),
       Description: client.description,
       Operations: client.methods
@@ -97,6 +100,7 @@ export function createModel(sdkContext: SdkContext<NetEmitterOptions>): CodeMode
             rootApiVersions,
             sdkContext,
             sdkTypeMap,
+            hook
           ),
         ),
       Protocol: {},
@@ -104,6 +108,7 @@ export function createModel(sdkContext: SdkContext<NetEmitterOptions>): CodeMode
       Parameters: clientParameters,
       Decorators: client.decorators,
     };
+    return hook?.emitClient ? hook.emitClient(client, unbrandingClient) : unbrandingClient;
   }
 
   function getClientName(
diff --git a/packages/http-client-csharp/emitter/src/lib/operation-converter.ts b/packages/http-client-csharp/emitter/src/lib/operation-converter.ts
index 92bc515e78..a56a297d0e 100644
--- a/packages/http-client-csharp/emitter/src/lib/operation-converter.ts
+++ b/packages/http-client-csharp/emitter/src/lib/operation-converter.ts
@@ -41,14 +41,16 @@ import { fromSdkHttpExamples } from "./example-converter.js";
 import { Logger } from "./logger.js";
 import { getInputType } from "./model.js";
 import { capitalize, isSdkPathParameter } from "./utils.js";
+import { CodeModelType, Hook } from "../emitter.js";
 
-export function fromSdkServiceMethod(
+export function fromSdkServiceMethod<T extends CodeModelType>(
   method: SdkServiceMethod<SdkHttpOperation>,
   uri: string,
   clientParameters: InputParameter[],
   rootApiVersions: string[],
   sdkContext: SdkContext<NetEmitterOptions>,
   typeMap: SdkTypeMap,
+  hook?: Hook<T>
 ): InputOperation {
   let generateConvenience = shouldGenerateConvenient(sdkContext, method.operation.__raw.operation);
   if (method.operation.verb === "patch" && generateConvenience) {
@@ -69,7 +71,7 @@ export function fromSdkServiceMethod(
     sdkContext,
     typeMap,
   );
-  return {
+  const unbrandingOperation = {
     Name: method.name,
     ResourceName:
       getResourceOperation(sdkContext.program, method.operation.__raw.operation)?.resourceType
@@ -106,6 +108,7 @@ export function fromSdkServiceMethod(
         )
       : undefined,
   };
+  return hook?.emitOperation ? hook.emitOperation(method, unbrandingOperation) : unbrandingOperation;
 }
 
 export function getParameterDefaultValue(
diff --git a/packages/http-client-csharp/generator/TestProjects/Local/Unbranded-TypeSpec/tspCodeModel.json b/packages/http-client-csharp/generator/TestProjects/Local/Unbranded-TypeSpec/tspCodeModel.json
index c8f4572fc3..8b43fa1453 100644
--- a/packages/http-client-csharp/generator/TestProjects/Local/Unbranded-TypeSpec/tspCodeModel.json
+++ b/packages/http-client-csharp/generator/TestProjects/Local/Unbranded-TypeSpec/tspCodeModel.json
@@ -1997,7 +1997,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.sayHi",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "205",
@@ -2151,7 +2152,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.helloAgain",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "218",
@@ -2306,7 +2308,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": false,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.noContentType",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "231",
@@ -2371,7 +2374,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.helloDemo2",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "236",
@@ -2484,7 +2488,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.createLiteral",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "245",
@@ -2630,7 +2635,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.helloLiteral",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "259",
@@ -2724,7 +2730,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.topAction",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "267",
@@ -2789,7 +2796,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": false,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.topAction2",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "272",
@@ -2902,7 +2910,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": false,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.patchAction",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "281",
@@ -3015,7 +3024,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.anonymousBody",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "290",
@@ -3128,7 +3138,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.friendlyModel",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "299",
@@ -3188,7 +3199,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.addTimeHeader",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "304",
@@ -3301,7 +3313,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.projectedNameModel",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "313",
@@ -3366,7 +3379,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.returnsAnonymousModel",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "318",
@@ -3442,7 +3456,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.getUnknownValue",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "324",
@@ -3555,7 +3570,8 @@
      "GenerateProtocolMethod": false,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.internalProtocol",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "333",
@@ -3587,7 +3603,8 @@
      "GenerateProtocolMethod": false,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.stillConvenient",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "335",
@@ -3640,7 +3657,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.headAsBoolean",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     },
     {
      "$id": "339",
@@ -3724,7 +3742,8 @@
      "GenerateProtocolMethod": true,
      "GenerateConvenienceMethod": true,
      "CrossLanguageDefinitionId": "UnbrandedTypeSpec.WithApiVersion",
-     "Decorators": []
+     "Decorators": [],
+     "AzureStuff": "hello azure"
     }
    ],
    "Protocol": {
@@ -3735,7 +3754,8 @@
      "$ref": "193"
     }
    ],
-   "Decorators": []
+   "Decorators": [],
+   "AzureStuff": "hello azure"
   }
  ],
  "Auth": {