# Ejemplo: operaciones CRUD con la API de bajo nivel de AWS SDK para .NET
<a name="LowLevelDotNetItemsExample"></a>

En el siguiente ejemplo de código C\$1 se ilustran las operaciones de creación, lectura, actualización y eliminación (CRUD, Create, Read, Update and Delete) en un elemento de Amazon DynamoDB. En el ejemplo se agrega un elemento a la tabla `ProductCatalog`, se recupera, se llevan a cabo varias actualizaciones y, por último, se elimina. Si no ha creado esta tabla, también puede crearla mediante programación. Para obtener más información, consulte [Creación de ejemplos de tablas y carga de datos utilizando AWS SDK para .NET](AppendixSampleDataCodeDotNET.md).

Para obtener instrucciones paso a paso para probar el siguiente ejemplo, consulte [Ejemplos de código .NET](CodeSamples.DotNet.md). 

**Example**  

```
using System;
using System.Collections.Generic;
using Amazon.DynamoDBv2;
using Amazon.DynamoDBv2.Model;
using Amazon.Runtime;
using Amazon.SecurityToken;

namespace com.amazonaws.codesamples
{
    class LowLevelItemCRUDExample
    {
        private static string tableName = "ProductCatalog";
        private static AmazonDynamoDBClient client = new AmazonDynamoDBClient();

        static void Main(string[] args)
        {
            try
            {
                CreateItem();
                RetrieveItem();

                // Perform various updates.
                UpdateMultipleAttributes();
                UpdateExistingAttributeConditionally();

                // Delete item.
                DeleteItem();
                Console.WriteLine("To continue, press Enter");
                Console.ReadLine();
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                Console.WriteLine("To continue, press Enter");
                Console.ReadLine();
            }
        }

        private static void CreateItem()
        {
            var request = new PutItemRequest
            {
                TableName = tableName,
                Item = new Dictionary<string, AttributeValue>()
            {
                { "Id", new AttributeValue {
                      N = "1000"
                  }},
                { "Title", new AttributeValue {
                      S = "Book 201 Title"
                  }},
                { "ISBN", new AttributeValue {
                      S = "11-11-11-11"
                  }},
                { "Authors", new AttributeValue {
                      SS = new List<string>{"Author1", "Author2" }
                  }},
                { "Price", new AttributeValue {
                      N = "20.00"
                  }},
                { "Dimensions", new AttributeValue {
                      S = "8.5x11.0x.75"
                  }},
                { "InPublication", new AttributeValue {
                      BOOL = false
                  } }
            }
            };
            client.PutItem(request);
        }

        private static void RetrieveItem()
        {
            var request = new GetItemRequest
            {
                TableName = tableName,
                Key = new Dictionary<string, AttributeValue>()
            {
                { "Id", new AttributeValue {
                      N = "1000"
                  } }
            },
                ProjectionExpression = "Id, ISBN, Title, Authors",
                ConsistentRead = true
            };
            var response = client.GetItem(request);

            // Check the response.
            var attributeList = response.Item; // attribute list in the response.
            Console.WriteLine("\nPrinting item after retrieving it ............");
            PrintItem(attributeList);
        }

        private static void UpdateMultipleAttributes()
        {
            var request = new UpdateItemRequest
            {
                Key = new Dictionary<string, AttributeValue>()
            {
                { "Id", new AttributeValue {
                      N = "1000"
                  } }
            },
                // Perform the following updates:
                // 1) Add two new authors to the list
                // 1) Set a new attribute
                // 2) Remove the ISBN attribute
                ExpressionAttributeNames = new Dictionary<string, string>()
            {
                {"#A","Authors"},
                {"#NA","NewAttribute"},
                {"#I","ISBN"}
            },
                ExpressionAttributeValues = new Dictionary<string, AttributeValue>()
            {
                {":auth",new AttributeValue {
                     SS = {"Author YY", "Author ZZ"}
                 }},
                {":new",new AttributeValue {
                     S = "New Value"
                 }}
            },

                UpdateExpression = "ADD #A :auth SET #NA = :new REMOVE #I",

                TableName = tableName,
                ReturnValues = "ALL_NEW" // Give me all attributes of the updated item.
            };
            var response = client.UpdateItem(request);

            // Check the response.
            var attributeList = response.Attributes; // attribute list in the response.
                                                     // print attributeList.
            Console.WriteLine("\nPrinting item after multiple attribute update ............");
            PrintItem(attributeList);
        }

        private static void UpdateExistingAttributeConditionally()
        {
            var request = new UpdateItemRequest
            {
                Key = new Dictionary<string, AttributeValue>()
            {
                { "Id", new AttributeValue {
                      N = "1000"
                  } }
            },
                ExpressionAttributeNames = new Dictionary<string, string>()
            {
                {"#P", "Price"}
            },
                ExpressionAttributeValues = new Dictionary<string, AttributeValue>()
            {
                {":newprice",new AttributeValue {
                     N = "22.00"
                 }},
                {":currprice",new AttributeValue {
                     N = "20.00"
                 }}
            },
                // This updates price only if current price is 20.00.
                UpdateExpression = "SET #P = :newprice",
                ConditionExpression = "#P = :currprice",

                TableName = tableName,
                ReturnValues = "ALL_NEW" // Give me all attributes of the updated item.
            };
            var response = client.UpdateItem(request);

            // Check the response.
            var attributeList = response.Attributes; // attribute list in the response.
            Console.WriteLine("\nPrinting item after updating price value conditionally ............");
            PrintItem(attributeList);
        }

        private static void DeleteItem()
        {
            var request = new DeleteItemRequest
            {
                TableName = tableName,
                Key = new Dictionary<string, AttributeValue>()
            {
                { "Id", new AttributeValue {
                      N = "1000"
                  } }
            },

                // Return the entire item as it appeared before the update.
                ReturnValues = "ALL_OLD",
                ExpressionAttributeNames = new Dictionary<string, string>()
            {
                {"#IP", "InPublication"}
            },
                ExpressionAttributeValues = new Dictionary<string, AttributeValue>()
            {
                {":inpub",new AttributeValue {
                     BOOL = false
                 }}
            },
                ConditionExpression = "#IP = :inpub"
            };

            var response = client.DeleteItem(request);

            // Check the response.
            var attributeList = response.Attributes; // Attribute list in the response.
                                                     // Print item.
            Console.WriteLine("\nPrinting item that was just deleted ............");
            PrintItem(attributeList);
        }

        private static void PrintItem(Dictionary<string, AttributeValue> attributeList)
        {
            foreach (KeyValuePair<string, AttributeValue> kvp in attributeList)
            {
                string attributeName = kvp.Key;
                AttributeValue value = kvp.Value;

                Console.WriteLine(
                    attributeName + " " +
                    (value.S == null ? "" : "S=[" + value.S + "]") +
                    (value.N == null ? "" : "N=[" + value.N + "]") +
                    (value.SS == null ? "" : "SS=[" + string.Join(",", value.SS.ToArray()) + "]") +
                    (value.NS == null ? "" : "NS=[" + string.Join(",", value.NS.ToArray()) + "]")
                    );
            }
            Console.WriteLine("************************************************");
        }
    }
}
```