diff --git a/src/common/enums/message.enum.ts b/src/common/enums/message.enum.ts
index e992f6f..8bf57e4 100755
--- a/src/common/enums/message.enum.ts
+++ b/src/common/enums/message.enum.ts
@@ -933,5 +933,11 @@ export const enum ProjectMessage {
 }
 
 export const enum TaskPhaseMessage {
-  TASK_PHASE_NOT_FOUND = "فاز تسک مورد نظر پیدا نشد!"
+  TASK_PHASE_NOT_FOUND = "فاز تسک مورد نظر پیدا نشد!",
+  TASK_PHASE_NOT_SAME_PROJECT = "فاز تسک جدید با فاز تسک قبلی در یک پروژه نیستند!"
+}
+
+export const enum TaskMessage {
+  TASK_NOT_FOUND = "تسک مورد نظر پیدا نشد!",
+  USERS_ASSIGNED_TO_TASK_NOT_PROJECT_MEMBER = "حداقل یکی از کاربران تعیین شده عضو پروژه نیستند!"
 }
\ No newline at end of file
diff --git a/src/modules/task-manager/controllers/task-phase.controller.ts b/src/modules/task-manager/controllers/task-phase.controller.ts
index 32f83c9..5e3fd3d 100644
--- a/src/modules/task-manager/controllers/task-phase.controller.ts
+++ b/src/modules/task-manager/controllers/task-phase.controller.ts
@@ -32,7 +32,7 @@ export class TaskPhaseController {
   @ApiResponse({ status: 200, description: "TaskPhase found", type: TMTaskPhase })
   @ApiResponse({ status: 404, description: "TaskPhase not found" })
   findOne(@Param("id") id: string): Promise<TMTaskPhase> {
-    return this.taskPhaseService.findOne(id);
+    return this.taskPhaseService.findOneOrFail(id);
   }
 
   @Post()
diff --git a/src/modules/task-manager/controllers/task.controller.ts b/src/modules/task-manager/controllers/task.controller.ts
index 9e356b3..c0fa93d 100644
--- a/src/modules/task-manager/controllers/task.controller.ts
+++ b/src/modules/task-manager/controllers/task.controller.ts
@@ -26,7 +26,7 @@ export class TaskController {
   @ApiResponse({ status: 200, description: 'Task found', type: TMTask })
   @ApiResponse({ status: 404, description: 'Task not found' })
   findOne(@Param('id') id: string): Promise<TMTask> {
-    return this.taskService.findOne(id);
+    return this.taskService.findOneOrFail(id);
   }
 
   @Post()
diff --git a/src/modules/task-manager/providers/task-phase.service.ts b/src/modules/task-manager/providers/task-phase.service.ts
index 00bcf63..11233ee 100644
--- a/src/modules/task-manager/providers/task-phase.service.ts
+++ b/src/modules/task-manager/providers/task-phase.service.ts
@@ -23,7 +23,7 @@ export class TaskPhaseService {
     });
   }
 
-  async findOne(id: string): Promise<TMTaskPhase> {
+  async findOneOrFail(id: string): Promise<TMTaskPhase> {
     const taskPhase = await this.taskPhaseRepository.findOne({where: {id}});
     if (!taskPhase) throw new NotFoundException(TaskPhaseMessage.TASK_PHASE_NOT_FOUND);
     return taskPhase;
@@ -36,7 +36,7 @@ export class TaskPhaseService {
   }
 
   async update(id: string, dto: UpdateTaskPhaseDto): Promise<TMTaskPhase> {
-    const taskPhase = await this.findOne(id);
+    const taskPhase = await this.findOneOrFail(id);
 
     if (dto.projectId) {
       await this.projectService.findOneOrFail(dto.projectId);
@@ -47,7 +47,7 @@ export class TaskPhaseService {
   }
 
   async remove(id: string): Promise<void> {
-    await this.findOne(id);
+    await this.findOneOrFail(id);
     await this.taskPhaseRepository.delete(id);
   }
 }
diff --git a/src/modules/task-manager/providers/task.service.ts b/src/modules/task-manager/providers/task.service.ts
index 9e635e3..2be9e15 100644
--- a/src/modules/task-manager/providers/task.service.ts
+++ b/src/modules/task-manager/providers/task.service.ts
@@ -1,13 +1,15 @@
-import { BadRequestException, Injectable, NotFoundException } from '@nestjs/common';
-import { InjectRepository } from '@nestjs/typeorm';
-import { In, Repository } from 'typeorm';
-import { TaskRepository } from '../repositories/task.repository';
-import { TaskPhaseRepository } from '../repositories/task-phase.repository';
-import { TMTask } from '../entities/task.entity';
-import { CreateTaskDto } from '../dto/task/create-task.dto';
-import { UpdateTaskDto } from '../dto/task/update-task.dto';
-import { ChangeTaskPhaseDto } from '../dto/task/change-task-phase.dto';
-import { User } from '../../users/entities/user.entity';
+import { BadRequestException, Injectable, NotFoundException } from "@nestjs/common";
+import { InjectRepository } from "@nestjs/typeorm";
+import { In, Repository } from "typeorm";
+import { TaskRepository } from "../repositories/task.repository";
+import { TMTask } from "../entities/task.entity";
+import { CreateTaskDto } from "../dto/task/create-task.dto";
+import { UpdateTaskDto } from "../dto/task/update-task.dto";
+import { ChangeTaskPhaseDto } from "../dto/task/change-task-phase.dto";
+import { User } from "../../users/entities/user.entity";
+import { TaskMessage, TaskPhaseMessage } from "../../../common/enums/message.enum";
+import { TaskPhaseRepository } from "../repositories/task-phase.repository";
+import { TMTaskPhase } from "../entities/task-phase.entity";
 
 @Injectable()
 export class TaskService {
@@ -18,25 +20,50 @@ export class TaskService {
     private readonly userRepository: Repository<User>,
   ) {}
 
-  findAll(): Promise<TMTask[]> {
-    return this.taskRepository.findAll();
+  async findAll(): Promise<TMTask[]> {
+    return this.taskRepository.find({
+      relations: ["taskPhase", "remarks", "attachments", "checkListItems", "users"],
+    });
   }
 
-  findByPhase(taskPhaseId: string): Promise<TMTask[]> {
-    return this.taskRepository.findByPhase(taskPhaseId);
+  async findByPhase(taskPhaseId: string): Promise<TMTask[]> {
+    return this.taskRepository.find({ where: { taskPhaseId } });
   }
 
-  async findOne(id: string): Promise<TMTask> {
-    const task = await this.taskRepository.findOneById(id);
-    if (!task) throw new NotFoundException(`Task #${id} not found`);
+  async findOneOrFail(id: string): Promise<TMTask> {
+    const task = await this.taskRepository.findOne({
+      where: { id },
+      relations: {
+        taskPhase: true,
+      },
+    });
+    if (!task) throw new NotFoundException(TaskMessage.TASK_NOT_FOUND);
     return task;
   }
 
+  async findTaskPhaseOrFail(taskPhaseId: string): Promise<TMTaskPhase> {
+    const taskPhase = await this.taskPhaseRepository.findOne({
+      where: { id: taskPhaseId },
+      relations: {
+        project: {
+          users: true,
+        },
+      },
+    });
+    if (!taskPhase) throw new NotFoundException(TaskPhaseMessage.TASK_PHASE_NOT_FOUND);
+
+    return taskPhase;
+  }
+
   async create(dto: CreateTaskDto): Promise<TMTask> {
     const { userIds, startDate, endDate, ...rest } = dto;
 
-    const taskPhase = await this.taskPhaseRepository.findOneById(dto.taskPhaseId);
-    if (!taskPhase) throw new NotFoundException(`TaskPhase #${dto.taskPhaseId} not found`);
+    const taskPhase = await this.findTaskPhaseOrFail(dto.taskPhaseId);
+
+    if (userIds?.length) {
+      const isUsersValid = userIds.every((userId) => taskPhase.project.users.some((user) => user.id === userId));
+      if (!isUsersValid) throw new BadRequestException(TaskMessage.USERS_ASSIGNED_TO_TASK_NOT_PROJECT_MEMBER);
+    }
 
     const task = this.taskRepository.create({
       ...rest,
@@ -52,12 +79,16 @@ export class TaskService {
   }
 
   async update(id: string, dto: UpdateTaskDto): Promise<TMTask> {
-    const task = await this.findOne(id);
+    const task = await this.findOneOrFail(id);
     const { userIds, startDate, endDate, ...rest } = dto;
 
     if (dto.taskPhaseId) {
-      const taskPhase = await this.taskPhaseRepository.findOneById(dto.taskPhaseId);
-      if (!taskPhase) throw new NotFoundException(`TaskPhase #${dto.taskPhaseId} not found`);
+      const taskPhase = await this.findTaskPhaseOrFail(dto.taskPhaseId);
+
+      if (userIds?.length) {
+        const isUsersValid = userIds.every((userId) => taskPhase.project.users.some((user) => user.id === userId));
+        if (!isUsersValid) throw new BadRequestException(TaskMessage.USERS_ASSIGNED_TO_TASK_NOT_PROJECT_MEMBER);
+      }
     }
 
     Object.assign(task, {
@@ -67,24 +98,19 @@ export class TaskService {
     });
 
     if (userIds) {
-      task.users = userIds.length
-        ? await this.userRepository.findBy({ id: In(userIds) })
-        : [];
+      task.users = userIds.length ? await this.userRepository.findBy({ id: In(userIds) }) : [];
     }
 
     return this.taskRepository.save(task);
   }
 
   async changePhase(id: string, dto: ChangeTaskPhaseDto): Promise<TMTask> {
-    const task = await this.findOne(id);
+    const task = await this.findOneOrFail(id);
 
-    const newPhase = await this.taskPhaseRepository.findOneById(dto.taskPhaseId);
-    if (!newPhase) throw new NotFoundException(`TaskPhase #${dto.taskPhaseId} not found`);
+    const newPhase = await this.findTaskPhaseOrFail(dto.taskPhaseId);
 
     if (task.taskPhase.projectId !== newPhase.projectId) {
-      throw new BadRequestException(
-        `TaskPhase #${dto.taskPhaseId} does not belong to the same project as the current phase`,
-      );
+      throw new BadRequestException(TaskPhaseMessage.TASK_PHASE_NOT_SAME_PROJECT);
     }
 
     task.taskPhaseId = dto.taskPhaseId;
@@ -94,7 +120,7 @@ export class TaskService {
   }
 
   async remove(id: string): Promise<void> {
-    await this.findOne(id);
+    await this.findOneOrFail(id);
     await this.taskRepository.delete(id);
   }
-}
\ No newline at end of file
+}
diff --git a/src/modules/task-manager/repositories/task.repository.ts b/src/modules/task-manager/repositories/task.repository.ts
index f419845..5f07518 100644
--- a/src/modules/task-manager/repositories/task.repository.ts
+++ b/src/modules/task-manager/repositories/task.repository.ts
@@ -4,45 +4,10 @@ import { Repository } from "typeorm";
 import { TMTask } from "../entities/task.entity";
 
 @Injectable()
-export class TaskRepository {
+export class TaskRepository extends Repository<TMTask> {
   constructor(
-    @InjectRepository(TMTask)
-    private readonly repository: Repository<TMTask>,
-  ) {}
-
-  findAll() {
-    return this.repository.find({
-      relations: ["taskPhase", "remarks", "attachments", "checkListItems", "users"],
-    });
-  }
-
-  findByPhase(taskPhaseId: string) {
-    return this.repository.find({
-      where: { taskPhaseId },
-      relations: ["remarks", "attachments", "checkListItems", "users"],
-    });
-  }
-
-  findOneById(id: string) {
-    return this.repository.findOne({
-      where: { id },
-      relations: ["taskPhase", "remarks", "attachments", "checkListItems", "users"],
-    });
-  }
-
-  create(data: Partial<TMTask>) {
-    return this.repository.create(data);
-  }
-
-  save(task: TMTask) {
-    return this.repository.save(task);
-  }
-
-  update(id: string, data: Partial<TMTask>) {
-    return this.repository.update(id, data);
-  }
-
-  delete(id: string) {
-    return this.repository.delete(id);
+    @InjectRepository(TMTask) taskRepository: Repository<TMTask>,
+  ) {
+    super(taskRepository.target, taskRepository.manager, taskRepository.queryRunner)
   }
 }