Example: CRUD operations using the AWS SDK for .NET document model

The following C# code example performs the following actions:

• Creates a book item in the ProductCatalog table.

• Retrieves the book item.

• Updates the book item. The code example shows a normal update that adds new attributes and updates existing attributes. It also shows a conditional update that updates the book price only if the existing price value is as specified in the code.

• Deletes the book item.

For step-by-step instructions to test the following example, see .NET code examples.

Example

/**
 * Copyright 2010-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * This file is licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License. A copy of
 * the License is located at
 *
 * http://aws.amazon.com/apache2.0/
 *
 * This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
*/
using System;
using System.Collections.Generic;
using System.Linq;
using Amazon.DynamoDBv2;
using Amazon.DynamoDBv2.DocumentModel;
using Amazon.Runtime;

namespace com.amazonaws.codesamples
{
    class MidlevelItemCRUD
    {
        private static AmazonDynamoDBClient client = new AmazonDynamoDBClient();
        private static string tableName = "ProductCatalog";
        // The sample uses the following id PK value to add book item.
        private static int sampleBookId = 555;

        static void Main(string[] args)
        {
            try
            {
                Table productCatalog = Table.LoadTable(client, tableName);
                CreateBookItem(productCatalog);
                RetrieveBook(productCatalog);
                // Couple of sample updates.
                UpdateMultipleAttributes(productCatalog);
                UpdateBookPriceConditionally(productCatalog);

                // Delete.
                DeleteBook(productCatalog);
                Console.WriteLine("To continue, press Enter");
                Console.ReadLine();
            }
            catch (AmazonDynamoDBException e) { Console.WriteLine(e.Message); }
            catch (AmazonServiceException e) { Console.WriteLine(e.Message); }
            catch (Exception e) { Console.WriteLine(e.Message); }
        }

        // Creates a sample book item.
        private static void CreateBookItem(Table productCatalog)
        {
            Console.WriteLine("\n*** Executing CreateBookItem() ***");
            var book = new Document();
            book["Id"] = sampleBookId;
            book["Title"] = "Book " + sampleBookId;
            book["Price"] = 19.99;
            book["ISBN"] = "111-1111111111";
            book["Authors"] = new List<string> { "Author 1", "Author 2", "Author 3" };
            book["PageCount"] = 500;
            book["Dimensions"] = "8.5x11x.5";
            book["InPublication"] = new DynamoDBBool(true);
            book["InStock"] = new DynamoDBBool(false);
            book["QuantityOnHand"] = 0;

            productCatalog.PutItem(book);
        }

        private static void RetrieveBook(Table productCatalog)
        {
            Console.WriteLine("\n*** Executing RetrieveBook() ***");
            // Optional configuration.
            GetItemOperationConfig config = new GetItemOperationConfig
            {
                AttributesToGet = new List<string> { "Id", "ISBN", "Title", "Authors", "Price" },
                ConsistentRead = true
            };
            Document document = productCatalog.GetItem(sampleBookId, config);
            Console.WriteLine("RetrieveBook: Printing book retrieved...");
            PrintDocument(document);
        }

        private static void UpdateMultipleAttributes(Table productCatalog)
        {
            Console.WriteLine("\n*** Executing UpdateMultipleAttributes() ***");
            Console.WriteLine("\nUpdating multiple attributes....");
            int partitionKey = sampleBookId;

            var book = new Document();
            book["Id"] = partitionKey;
            // List of attribute updates.
            // The following replaces the existing authors list.
            book["Authors"] = new List<string> { "Author x", "Author y" };
            book["newAttribute"] = "New Value";
            book["ISBN"] = null; // Remove it.

            // Optional parameters.
            UpdateItemOperationConfig config = new UpdateItemOperationConfig
            {
                // Get updated item in response.
                ReturnValues = ReturnValues.AllNewAttributes
            };
            Document updatedBook = productCatalog.UpdateItem(book, config);
            Console.WriteLine("UpdateMultipleAttributes: Printing item after updates ...");
            PrintDocument(updatedBook);
        }

        private static void UpdateBookPriceConditionally(Table productCatalog)
        {
            Console.WriteLine("\n*** Executing UpdateBookPriceConditionally() ***");

            int partitionKey = sampleBookId;

            var book = new Document();
            book["Id"] = partitionKey;
            book["Price"] = 29.99;

            // For conditional price update, creating a condition expression.
            Expression expr = new Expression();
            expr.ExpressionStatement = "Price = :val";
            expr.ExpressionAttributeValues[":val"] = 19.00;

            // Optional parameters.
            UpdateItemOperationConfig config = new UpdateItemOperationConfig
            {
                ConditionalExpression = expr,
                ReturnValues = ReturnValues.AllNewAttributes
            };
            Document updatedBook = productCatalog.UpdateItem(book, config);
            Console.WriteLine("UpdateBookPriceConditionally: Printing item whose price was conditionally updated");
            PrintDocument(updatedBook);
        }

        private static void DeleteBook(Table productCatalog)
        {
            Console.WriteLine("\n*** Executing DeleteBook() ***");
            // Optional configuration.
            DeleteItemOperationConfig config = new DeleteItemOperationConfig
            {
                // Return the deleted item.
                ReturnValues = ReturnValues.AllOldAttributes
            };
            Document document = productCatalog.DeleteItem(sampleBookId, config);
            Console.WriteLine("DeleteBook: Printing deleted just deleted...");
            PrintDocument(document);
        }

        private static void PrintDocument(Document updatedDocument)
        {
            foreach (var attribute in updatedDocument.GetAttributeNames())
            {
                string stringValue = null;
                var value = updatedDocument[attribute];
                if (value is Primitive)
                    stringValue = value.AsPrimitive().Value.ToString();
                else if (value is PrimitiveList)
                    stringValue = string.Join(",", (from primitive
                                    in value.AsPrimitiveList().Entries
                                                    select primitive.Value).ToArray());
                Console.WriteLine("{0} - {1}", attribute, stringValue);
            }
        }
    }
}