适用于 Xamarin 的 AWS 移动 SDK 现已包含在。 适用于 .NET 的 AWS SDK本指南参考了适用于 Xamarin 的 Mobile SDK 的存档版本。

本文属于机器翻译版本。若本译文内容与英语原文存在差异，则一律以英文原文为准。

# 使用文档模型
<a name="dynamodb-integration-docmodel"></a>

文档模型围绕低级别 .NET API 提供封装类。表和文档是主要的封装类。您可以使用文档模型创建、检索、更新和删除项目。要创建、更新和删除表，您必须使用低级别 API。有关如何使用低级 API 的说明，请参阅[使用 DynamoDB 服务](dynamodb-integration-lowlevelapi.md)级别。 APIs低级 API 已在 Amazon.dynamoDB 中提供。 DocumentModel 命名空间。

要了解有关文档模型的更多信息，请参阅 [.NET 文档模型](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/DotNetSDKMidLevel.html)。

## 创建 DynamoDB 客户端
<a name="create-a-dynamodb-client"></a>

创建 DynamoDB 客户端：

```
var client = new AmazonDynamoDBClient(credentials,region);
DynamoDBContext context = new DynamoDBContext(client);
```

## CRUD 操作
<a name="crud-operations"></a>

### 保存项目
<a name="save-an-item"></a>

创建项目：

```
Table table = Table.LoadTable(client, "Books");
id = Guid.NewGuid().ToString();
var books = new Document();
books["Id"] = id;
books["Author"] = "Mark Twain";
books["Title"] = "Adventures of Huckleberry Finn";
books["ISBN"] = "112-111111";
books["Price"] = "10";
```

将项目保存到 DynamoDB 表中：

```
var book = await table.PutItemAsync(books);
```

### 检索项目
<a name="retrieve-an-item"></a>

检索项目：

```
public async Task GetItemAsync(AWSCredentials credentials, RegionEndpoint region)
{
      var client = new AmazonDynamoDBClient(credentials, region);
      Table books = Table.LoadTable(client, "Books");
      var book = await books.GetItemAsync(id);
}
```

### 更新项目
<a name="update-an-item"></a>

如何更新项目:

```
public async Task UpdateItemAttributesAsync(AWSCredentials credentials, RegionEndpoint region)
{
      var book = new Document();
      book["Id"] = id;
      book["PageCount"] = "200";
      var client = new AmazonDynamoDBClient(credentials, region);
      Table books = Table.LoadTable(client, "Books");
      Document updatedBook = await books.UpdateItemAsync(book);
}
```

有条件更新项目：

```
public async Task UpdateItemConditionallyAsync(AWSCredentials credentials, RegionEndpoint region) {
      var book = new Document();
      book["Id"] = id;
      book["Price"] = "30";

      // For conditional price update, creating a condition expression.
      Expression expr = new Expression();
      expr.ExpressionStatement = "Price = :val";
      expr.ExpressionAttributeValues[":val"] = 10.00;

      var client = new AmazonDynamoDBClient(credentials, region);
      Table books = Table.LoadTable(client, "Books");

      Document updatedBook = await books.UpdateItemAsync(book);
}
```

### 删除项目
<a name="delete-an-item"></a>

如何删除项目:

```
public async Task DeleteItemAsync(AWSCredentials credentials, RegionEndpoint region)
{
  var client = new AmazonDynamoDBClient(credentials, region);
  Table books = Table.LoadTable(client, "Books");
  await books.DeleteItemAsync(id);
}
```

### 查询和扫描
<a name="query-and-scan"></a>

查询和检索作者为“Mark Twain”的所有图书：

```
public async Task QueryAsync(AWSCredentials credentials, RegionEndpoint region) {
  var client = new AmazonDynamoDBClient(credentials, region);
  Table books = Table.LoadTable(client, "Books");
  var search = books.Query(new QueryOperationConfig() {
   IndexName = "Author-Title-index",
   Filter = new QueryFilter("Author", QueryOperator.Equal, "Mark Twain")
  });
  Console.WriteLine("ScanAsync: printing query response");
  var documents = await search.GetRemainingAsync();
  documents.ForEach((d) = > {
   PrintDocument(d);
  });
}
```

下面的扫描示例代码返回我们的表中的所有图书：

```
public async Task ScanAsync(AWSCredentials credentials, RegionEndpoint region) {
      var client = new AmazonDynamoDBClient(credentials, region);
      Table books = Table.LoadTable(client, "Books");
      var search = books.Scan(new ScanOperationConfig() {
              ConsistentRead = true
      });
      Console.WriteLine("ScanAsync: printing scan response");
      var documents = await search.GetRemainingAsync();
      documents.ForEach((d) = > {
              PrintDocument(d);
      });
}
```