21 DynamoDB Query Code Examples .NET/C# (2023)

DynamoDB is a NoSQL database hosted in the Amazon cloud. It offers reliable performance, a well-managed environment, and easy API access to interact with it.

This article will help you perform various queries against DynamoDB using C#.

If you are looking for a similar guide but for Node.js,you can find it here, forrosa, and toPython/boto3 here.

DynamoDB C# Query Sample List

• Setting
• create table
• Consultation
• delete table
• delete element
• Scan
• Item Retrieval Using the Query Filter
• set item
• get all items
• Get all articles (with pagination)
• received a single item
• update article
• Retrieve items in batches
• Get items from multiple tables
• Batch write items
• execute transactions
• Run DynamoDB Local

Setting

To set up DynamoDB in the .NET environment, you need the AWSSDK.DynamoDBv2 package. Provides a .NET API that makes it easy to interact with DynamoDB to perform various query operations.

For the examples in this article, I use thelocal stackFrame. And the syntax remains the same for the actual DynamoDB instance by removing the service url parameter.

Let's see how to insert a new record and retrieve it by scanning the table or using a hash key.

Configuring the DynamoDB client

public Class Dynamo Client Configuration { Private read only AmazonDynamoDB client_amazonDynamoDBClient; Private read only DynamoDBContext_Context; public DynamoClient() { //localstack ignores secrets_amazonDynamoDBClient= nuevo AmazonDynamoDB client("Access ID", "awsSecretAccessKey", nuevo AmazonDynamoDBConfig {service url= "http://localhost:4569", //Standard-Localstack-URLUse HTTP= TRUE, });_Context= nuevo DynamoDBContext(_amazonDynamoDBClient, nuevo DynamoDBContextConfig {table name prefix= "proof_" }); }}

You must pass the accessId and accessKey to the AmazonDynamoDBClient constructor.

Create table and model class

To create the table, we are going to create the table creation request. To do this, we must specify all the declared keys of the table. If you have a lot of tables, this might be a bit formal; However, I will show several alternatives to make this process easier and faster in the future.

[DynamoDBTable("Employees")]public Class Look for: IEcuable<Employees> { [DynamoDBHashKey] public And tempId{ receive; Prayer; } public lineFirst name{ receive; Prayer; } public linelast name, last name{ receive; Prayer; } public bool Same(EmployeesOthers) { And (reference match(Null,Others)) go back INCORRECT; And (reference match(He,Others)) go back TRUE; go backID==Others.ID&& line.Same(First name,Others.First name) && line.Same(last name, last name,Others.last name, last name); } public overwrite bool Same(Objectobject) { And (reference match(Null,object)) go back INCORRECT; And (reference match(He,object)) go back TRUE; And (object.getType() != He.getType()) go back INCORRECT; go back Same((Student)object); } public overwrite And t get hash code() { rampant { GuerraHash code=empId;Hash code= (Hash code* 397) ^ (First name!= Null ?First name.get hash code() : 0);Hash code= (Hash code* 397) ^ (last name, last name!= Null ?last name, last name.get hash code() : 0); go backHash code; } }}

There are two unique attributes that we can use.

• DynamoDBTable--- Allocate the equivalent DynamoDB table.
• DynamoDBHashKey--- Assign the hash key of the table.

public asynchronous Task<CreateTableResponseCreateTableResponse> ConfigurationAsync() { GuerracreateTableRequest= nuevo CreateTableRequest {table name= "employee_test",attribute definitions= nuevo List<attribute definition> (),key scheme= nuevo List<KeySchemaElement> (),GlobalSecondaryIndexesGlobalSecondaryIndexes= nuevo List<Global Secondary Index> (),local secondary indexes= nuevo List<LocalSecondaryIndex> (),provisioned throughput= nuevo provisioned throughput {read capacity units= 1,Write Capacity Units= 1 } };createTableRequest.key scheme= nuevo [] { nuevo KeySchemaElement {attribute name= "same",key type=key type.HASHISH, }, }.List();createTableRequest.attribute definitions= nuevo [] { nuevo attribute definition {attribute name= "same",attribute type=ScalarAttributeType.norte, } }.List();}
(Video) Getting started with AWS DynamoDB in .NET

Consultation

DynamoDB allows queries not only against the index of the main table, but also againstLSI (local secondary indexes)YGSI (Global Secondary Indexes).

public asynchronous Task SaveOderUpdateStudent(EmployeesEmployees) { wait_Context.GuardarAsync(Employees);}public asynchronous Task<Employees> GetEmployeeUsingHashKey(And tID) { go back wait_Context.LoadAsync <Employees> (empId);}public asynchronous Task<Employees> ScanForEmployeeUsingFirstName(lineFirst name) { Guerralook for=_Context.ScanAsync <Employees> ( nuevo [] { nuevo scan condition ( name of(Employees.First name),scan operator.Same,First name) } ); GuerraResult= waitlook for.GetRemainingAsync(); go backResult.ErsteOderStandard();}
See Also
DynamoDB Joins [How To Guide with Query Examples]A better way to query DynamoDB data with SQL | technological objectiveAccelerate Your AWS DynamoDB QueriesDynamoDB Cheat Sheet: Everything You Need to Know About Amazon Dynamo DB for the AWS Certified Developer Associate 2020 Certification

• SaveOrUpdateEmployee – To save a new entity, run SaveAsync. Remember that SaveAsync creates or updates the record; If the form already exists, the execution of the method overwrites the data in the matching record.
• GetEmployeeUsingHashKey – This method retrieves the records using the hash key.
• ScanForEmployeeUsingFirstName scans the entire table for the first name.

delete table

[Http Delete]public asynchronous Task extinguish(lineFirst name) { wait_dynamoDbContexto.EliminarAsync <Employees> (empId,First name,last name, last name);}

The DeleteAsync method deletes an element by specifying the partition and range key or by using the element itself.

delete element

low level model

public asynchronous Task delete element(linetable name) { GuerraConsultation= nuevo DeleteItemRequest {table name=table name,Gusto= nuevo dictionary< line,Attribute> { { "same", nuevo Attribute {norte= "999" } } }, }; wait_dynamoDbClient.DeleteItemAsync(Consultation);}

object persistence model

You can map your client-side classes to Amazon DynamoDB tables using the AWS SDK for .Net object persistence mechanism. The element is assigned to each object instance in the corresponding tables. The object persistence model provides the DynamoDBContext class, an entry point to DynamoDB, for storing client-side objects in tables. This class connects to DynamoDB so that it can view tables, perform CRUD actions, and run queries.

public asynchronous Task delete element(Article requestarticle request) { wait_Context.EliminarAsync(article request);}

We can do the above using the same model, including the table name and partition key.

Avoid overwriting existing records

public asynchronous Task SaveOnlyEmployee(EmployeesEmployees) { Guerraidentity event table=Tisch.loadtable(_amazonDynamoDBClient, "employee_test"); GuerraExpression= nuevo Expression {ExpressionAttributeNamesExpressionAttributeNames= nuevo dictionary< line, line > { { "#Gusto", name of(Employees.empId) }, },ExpressionAttributeValuesExpressionAttributeValuesExpressionAttributeValues= { { ":Gusto",Employees.empId}, },Expression Statement= "attribute_doesn't_exist(#key) ODER #key <> :key", }; Guerradocument=_Context.Document(Employees); waitidentity event table.PutItemAsync(document, nuevo PutItemOperationConfig {conditional expression=Expression,return values=return values.none});}
(Video) Using Amazon DynamoDb for ASP.NET Framework Session State

We need to use conditional expressions in DynamoDB to avoid overrides. If we try to insert a record that already has a hash key into the table, aConditionalCheckFailedExceptionit's charged.

Scan

You can filter the scan results by specifying scan criteria. Each attribute in the table is used to evaluate the condition. Suppose you have a client-side class called EmployeeCategory that maps to the DynamoDB employee table. The following C# example searches the table and returns only employee IDs greater than 10.

IEnumerable<Employees>elements with wrong ID=context.Scan <Employees> ( nuevo scan condition("same",scan operator.Less than,empId), nuevo scan condition("Employee Category",scan operator.Same, "Internal"));

The Scan method returns an IEnumerable collection that has been "lazy loaded". Initially it just returns a page of results and then makes a service request for the next page if needed. You just need to iterate through the IEnumerable to get all the matching entries.

Get articles with query filter

object persistence model

public asynchronous Task<IEnumerable<Article request>> GetUsersItemsByName(And tempId, lineempname) { GuerraSetting= nuevo DynamoDBOperationConfig {query filter= nuevo List<scan condition> { nuevo scan condition("name of the job",scan operator.Starts with,empname) } }; go back wait_Context.QueryAsync <Article request> (empId,Setting).GetRemainingAsync();}

low level model

public asynchronous Task<consultanswer> Get items by name(And tempId, lineempname) { GuerraConsultation= nuevo consultaSolicitud {table name=table name,key condition expression= "id = :empId and starts_with (name,:empname)",ExpressionAttributeValuesExpressionAttributeValuesExpressionAttributeValues= nuevo dictionary< line,Attribute> { { ":ID", nuevo Attribute {norte=ID.Chain() } }, { ":Name", nuevo Attribute {S=empname} } } }; go back wait_dynamoDbClient.QueryAsync(Consultation);}

set item

Replace an old article with a new article or create a new article. If an item with the same primary key already exists in the mounted database, it will be completely replaced with the new item. You can insert a new element if the supplied primary key does not exist, or return an existing element if it contains specific attribute values.

You can use the returnValues ​​option to return the values ​​of the element's attributes in the same action as inserting the element.

Primary key attributes are the only attributes required when adding an item. Null values ​​are not allowed for attribute values. String length and binary properties must be greater than zero. There must be no empty record type attributes. ValidationException is thrown for requests with open values.

PutItem can return a copy of the old item (before the update) or a copy of the new item (after the update).

public virtual Empty CreateAccountItem(AmazonDynamoDB clientddb client, linetable name, AccountAccount) { // Create sales request GuerraputItemRequest= nuevo PutItemRequest {table name=table name,Article= nuevo dictionary< line,Attribute> { { "Company", nuevo Attribute {S=Account.Look for} }, { "Email", nuevo Attribute {S=Account.Email} } } }; // Only add attributes if the corresponding property on the Account object is not empty. And (!line.is null or empty(Account.First)) {putItemRequest.Article.add("First", nuevo Attribute {S=Account.First}); } And (!line.is null or empty(Account.Last)) {putItemRequest.Article.add("Last", nuevo Attribute {S=Account.Last}); } And (!line.is null or empty(Account.To alter)) {putItemRequest.Article.add("To alter", nuevo Attribute {norte=Account.To alter}); } // Send the requestddb client.also put(putItemRequest);}
(Video) AWS DynamoDB PAGINATION | .NET ON AWS | AWS Serverless | Amazon

get all items

Let's find all the items on the table.

GuerraEmployees= wait GetAllEmployees();console.Write line(Employees.paging token);console.Write line(Employees.result type);for each(GuerraempInEmployees.Employees) {console.Write line(ps{emp.Email address}-{emp.empId}-{emp.To alter}-{emp.united the}- ADDRESS:{emp.ADDRESS.Calle},{emp.ADDRESS.Ciudad}");}

Get all articles (with pagination)

The following code shows the functionality of the GetAllEmployees method. First you need to get the model table reference and look for a paging token. You can use paginationToken with the scan option to get the following result set.

public static asynchronous Task<Employee View Model> GetAllEmployees(linepaging token= "") { GuerraTisch=context.GetDestinationTable <Employees> (); //Get PaginationToken to use for scanning GuerrascanOps= nuevo ScanOperationConfig(); And (!line.is null or empty(paging token)) {scanOps.paging token=paging token; } // returns the set of Document objects for the provided ScanOptions GuerraResults=Tisch.Scan(scanOps); List<Document>Data= waitResults.GetNextSetAsync(); IEnumerable<Employees>Employees=context.of documents <Employees> (Data); // Pass the PaginationToken, if available, from the results along with the result set go back nuevo Employee View Model {paging token=Results.paging token,Employees=Employees,result type=result type.List};}

received a single item

console.Write line("unique result");Guerraemployees found= wait Einzel("100e4548-1f68-4288-972d-81133b6dacb1",Convert.HastaFechaHora("2021-01-01T06:43:18.014Z"));And (employees found!= Null) {console.Write line(ps{employees found.Email address}-{employees found.ID}-{employees found.united the}");}public static asynchronous Task<Employees> Einzel(lineemployee ID, appointment timeunited the) { go back waitcontext.LoadAsync <Employees> (employee ID,united the);}

update article

public static asynchronous Task Update(lineemployee ID, EmployeeInputModellegal entity) { GuerraEmployees= wait Einzel(employee ID,legal entity.united the);Employees.Email address=legal entity.Email address;Employees.Username=legal entity.Username;Employees.Name=legal entity.Name; waitcontext.GuardarAsync <Employees> (Employees);}

Get items in batches

The following code retrieves three items from the EmployeeDetails table in C#. The result elements arenot necessarily in the same order as the primary keys you choose.

DynamoDBContextcontext= nuevo DynamoDBContext(Client);Guerraemployee batch=context.CreateBatchGet <details about employees> ();employee batch.add key(001);employee batch.add key(002);employee batch.add key(003);employee batch.Accomplish();// Get the result setconsole.Write line(employee batch.Results.To count);Employeesemp1=employee batch.Results[0];Employeesemp2=employee batch.Results[1];Employeesmp3=employee batch.Results[2];

When trying to retrieve multiple items from a database table with one query, you should consider the following:

• You must create an instance of the CreateBatchGet class.
• We need to provide the list of primary keys.
• When you call the Execute method, the response returns the elements of the Result property.

Get items from multiple tables

Follow these steps to retrieve items from multiple tables:

• First, create an instance of CreateBatchGet type for each type and pass in the primary key values ​​you want to retrieve from each table.
• Create an instance of in one of the following waysMultiTableBatchGetclass: - Call the Combine function using one of the BatchGet objects you created in the previous step. - A list of BatchGet objects is used to create an instance of the MultiBatchGet type. - Pass your list of BatchGet objects to DynamoDBContext's CreateMultiTableBatchGet function.
• Call the Execute function of MultiTableBatchGet, which provides results written to individual BatchGet objects.

HeCreateBatchGetThe function is used in the following C# code to retrieve various items from the Employee and EmployeeWorkDetails databases.

Guerraemployee batch=context.CreateBatchGet <Employees> ();employee batch.add key(101);employee batch.add key(102);GuerraEmployeeJobDetailsLot=context.CreateBatchGet <Employee Job Details> ();EmployeeJobDetailsLot.add key(101, "P1");EmployeeJobDetailsLot.add key(101, "P2");EmployeeJobDetailsLot.add key(102, "P3");EmployeeJobDetailsLot.add key(102, "P1");GuerraEmployeesAndDetailSuperBatch=Employee Job Details.To combine(Employee Job Details);EmployeesAndDetailSuperBatch.Accomplish();console.Write line(employee batch.Results.To count);console.Write line(EmployeeJobDetailsLot.Results.To count);Employeesemp1=employee batch.Results[0];Employeesemp2=EmployeeJobDetailsLot.Results[1];EmployeeWorkDetailEmployeeWorkDetail=EmployeeJobDetailsLot.Results[0];

Batch write items

This section covers inserting and removing multiple items in a batch write operation. To insert or delete batch write, you need to pay attention to the following.

• First, call the CreateBatchWrite method on DynamoDB and create the BatchWrite class.
• Mention the items you need to add or remove. For this:
  • When inserting items, use the AddPutItem method or the AddPutItems method.
  • When you delete an item, you must specify the item's primary key or the client-side object associated with the item you want to delete. Use the AddDeleteItem, AddDeleteItems, and AddDeleteKey methods to specify the list of items to delete.
  • You can call BatchWrite.Execute, a method to insert or delete specific items in the table.

DynamoDBContextcontext= nuevo DynamoDBContext(Client);Guerralot of books=context.CreateBatchWrite <Employees> ();// Specify the employee to addEmployeesemp1= nuevo Employees {EmpId= 101,employee category= "Internal",Description= "Inside Employee 1"};Employeesemp2= nuevo Employees {EmpId= 102,employee category= "Internal",Description= "Inside Employee 2"};lot of books.Add sale items(nuevo List<Employees> {emp1,emp2});// Specify the employee to deleteemployee batch.AddDeleteKey(111);employee batch.Accomplish();

execute transactions

The following code snippet illustrates how transactions are performed in DynamoDB.

collection<TransactWriteItem>Behavior=arrangements.like a list( nuevo TransactWriteItem().mitConditionCheck(checkMitarbeiterValid), nuevo TransactWriteItem().mitUpdate(markItemSale), nuevo TransactWriteItem().mitPut(create order));TransactWriteItemsRequestplaceOrderTransaction= nuevo TransactWriteItemsRequest() .mitTransactItems(Behavior) .mitReturnConsumedCapacity(Return used capacity.TOTAL);// Execute the transaction and process the result.attempt {Client.transactWriteItems(placeOrderTransaction);System.outside.print("Succesful transaction");} catch (ResourceNotFoundExceptionrnf) {System.err.print("Could not find one of the tables involved in the transaction" +rnf.get message());} catch (InternalServerErrorExceptionwhile) {System.err.print("Internal Server Error" +while.get message());} catch (TransactionCanceledExceptiontce) {System.outside.print("Transaction canceled" +tce.get message());}

Run DynamoDB Local

By default, .NET Core loads app settings from a specific stream of sources. In our situation, when the program starts in the development environment (which is the default when debugging Visual Studio), the settings in this additional JSON file override the previous settings. For example, LocalMode was set to true and the service URL for the local DynamoDB instance was added.

We chose the value http://localhost:8000, but you can change this if you want to run the container on a different host port.

The following code shows how to register the DynamoDB service.

public Empty configure services(IServiceCollectionIServiceCollectionServices) { GuerradinamoDbConfig=Construction.GetSection("DinamoDb"); GuerrarunLocalDynamoDb=dinamoDbConfig.receive value < bool > ("local operation"); And (runLocalDynamoDb) {Services.add singleton <AmazonDynamoDB> (sp=> { GuerraclientConfig= nuevo AmazonDynamoDBConfig {service url=dinamoDbConfig.receive value < line > ("local service url") }; go back nuevo AmazonDynamoDB client(clientConfig); }); } Anders {Services.Add AWS service <AmazonDynamoDB> (); }Services.add mvc().Set Compatibility Version(compatibility version.Version_2_1);}

We can manually register a service for theAmazonDynamoDBinterface if thelocal operationIt's true. We use the overload to provide an implementation factory, which in this case returns the actual implementation. we use thatlocal service urlfrom configuration to creating an AmazonDynamoDBConfig instance in our scenario. We then use this configuration to create and return the AmazonDynamoDBClient. We've set this up as a singleton, which means this code will only be executed once when the service is in use.

If LocalMode is false, we need to use the AWS SDK helper methodAdd AWS serviceto add the service because we added thoseAWSSDK.Extensions.NETCore.ConfigurationPackage.

If you want to see your tables and local data in them, you can useDynobase to query and change items in spreadsheets offline.

learn more aboutRun DynamoDB locally.