使用文件模型 - AWS Mobile SDK
建立 DynamoDB 用户端CRUD 操作

Xamarin 的AWS行動 SDK 現在已包含在AWS SDK for .NET. 本指南參考 Xamarin 行動 SDK 的封存版本。

本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。

使用文件模型

文檔模型提供了圍繞低級別 .NET API 的包裝類。表和文檔是關鍵的包裝類。您可以使用文件模型來建立、檢索、更新和刪除項目。若要建立、更新和刪除資料表，您必須使用低階 API。如需如何使用低階 API 的資訊，請參使用 DynamoDB 服務級別 API。低階 API 在亞馬遜 DynamoDB 中提供。DocumentModel命名空間。

若要進一步了解文件模型，請參.NET 文件模型。

建立 DynamoDB 用户端

若要建立 DynamoDB 用户端，請執行下列

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

CRUD 操作

儲存項目

建立項目：

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";

將某個項目保存到 DynamoDB 資料表：

var book = await table.PutItemAsync(books);

擷取項目

要檢索項目：

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);
}

更新項目

若要更新項目：

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);
}

若要更新項目，請執行以下操作：

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);
}

刪除項目

若要刪除項目：

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

查詢和掃描

要查詢和檢索作者為「馬克·吐温」的所有圖書，請執行以下操作：

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);
  });
}

下面的掃描示例代碼返回我們表格中的所有圖書：

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);
      });
}