以下是一个使用Angular和MongoDB进行直接CRUD操作的解决方法，包含了代码示例：

1. 首先，确保你已经安装了Node.js和npm。

2. 创建一个新的Angular项目：

   ng new angular-mongodb-crud
   

3. 进入项目目录并安装相关依赖项：

   cd angular-mongodb-crud
   npm install mongodb express body-parser
   

4. 创建一个名为server.js的新文件，用于创建一个简单的Express服务器和MongoDB连接。

   const express = require('express');
   const mongodb = require('mongodb');
   const bodyParser = require('body-parser');
   
   const app = express();
   const mongoClient = mongodb.MongoClient;
   const mongoUrl = 'mongodb://localhost:27017';
   const dbName = 'angular-mongodb-crud';
   
   app.use(bodyParser.json());
   
   app.post('/api/create', (req, res) => {
     mongoClient.connect(mongoUrl, { useNewUrlParser: true }, (err, client) => {
       if (err) {
         console.log('Error while connecting to MongoDB:', err);
         res.status(500).json({ message: 'Error while connecting to MongoDB' });
       } else {
         const db = client.db(dbName);
         const collection = db.collection('items');
         collection.insertOne(req.body, (err, result) => {
           if (err) {
             console.log('Error while inserting item:', err);
             res.status(500).json({ message: 'Error while inserting item' });
           } else {
             res.status(200).json({ message: 'Item created successfully' });
           }
           client.close();
         });
       }
     });
   });
   
   app.get('/api/read', (req, res) => {
     mongoClient.connect(mongoUrl, { useNewUrlParser: true }, (err, client) => {
       if (err) {
         console.log('Error while connecting to MongoDB:', err);
         res.status(500).json({ message: 'Error while connecting to MongoDB' });
       } else {
         const db = client.db(dbName);
         const collection = db.collection('items');
         collection.find({}).toArray((err, items) => {
           if (err) {
             console.log('Error while reading items:', err);
             res.status(500).json({ message: 'Error while reading items' });
           } else {
             res.status(200).json(items);
           }
           client.close();
         });
       }
     });
   });
   
   app.put('/api/update/:id', (req, res) => {
     const itemId = req.params.id;
     mongoClient.connect(mongoUrl, { useNewUrlParser: true }, (err, client) => {
       if (err) {
         console.log('Error while connecting to MongoDB:', err);
         res.status(500).json({ message: 'Error while connecting to MongoDB' });
       } else {
         const db = client.db(dbName);
         const collection = db.collection('items');
         collection.updateOne({ _id: mongodb.ObjectID(itemId) }, { $set: req.body }, (err, result) => {
           if (err) {
             console.log('Error while updating item:', err);
             res.status(500).json({ message: 'Error while updating item' });
           } else {
             res.status(200).json({ message: 'Item updated successfully' });
           }
           client.close();
         });
       }
     });
   });
   
   app.delete('/api/delete/:id', (req, res) => {
     const itemId = req.params.id;
     mongoClient.connect(mongoUrl, { useNewUrlParser: true }, (err, client) => {
       if (err) {
         console.log('Error while connecting to MongoDB:', err);
         res.status(500).json({ message: 'Error while connecting to MongoDB' });
       } else {
         const db = client.db(dbName);
         const collection = db.collection('items');
         collection.deleteOne({ _id: mongodb.ObjectID(itemId) }, (err, result) => {
           if (err) {
             console.log('Error while deleting item:', err);
             res.status(500).json({ message: 'Error while deleting item' });
           } else {
             res.status(200).json({ message: 'Item deleted successfully' });
           }
           client.close();
         });
       }
     });
   });
   
   app.listen(3000, () => {
     console.log('Server listening on port 3000');
   });
   

5. 创建一个名为item.service.ts的新文件，用于在Angular中调用服务器上的API。