How to Build a Backend for Blazor?

introduction in this tutorial, you’ll learn how to build a complete backend for a blazor application using back4app we’ll walk through integrating essential back4app features such as database management, cloud code functions, rest and graphql apis, user authentication, and real time queries (live queries) to create a secure, scalable, and robust backend that seamlessly communicates with your blazor frontend leveraging back4app’s robust backend services with blazor, an asp net core framework for building interactive web uis using c#, enables developers to accelerate backend development whether you're building a blazor server app or a blazor webassembly app, the seamless integration with back4app can drastically reduce development time while ensuring high quality server side business logic by the end of this tutorial, you'll have built a secure backend structure tailored for a full stack web application using blazor you will gain insights on how to handle data operations, apply security controls, and implement cloud functions, making your blazor web application robust and scalable prerequisites to complete this tutorial, you will need a back4app account and a new back4app project getting started with back4app https //www back4app com/docs/get started/new parse app if you do not have an account, you can create one for free follow the guide above to get your project ready basic blazor development environment you can set this up by installing the latest net sdk from microsoft https //dotnet microsoft com/download and creating a new blazor project using templates like dotnet new blazorserver or dotnet new blazorwasm net sdk (version 6 or above) installed ensure you have the net sdk for building and running blazor apps familiarity with c# and blazor concepts blazor official documentation https //docs microsoft com/en us/aspnet/core/blazor/?view=aspnetcore 6 0 if you’re new to blazor, review the official docs or a beginner’s tutorial before starting ensure you have these prerequisites before starting to ensure a smooth tutorial experience step 1 – setting up back4app project create a new project the first step in building your blazor backend on back4app is creating a new project if you have not already created one, follow these steps log in to your back4app account click the “new app” button in your back4app dashboard give your app a name (e g , “blazor backend tutorial”) once the project is created, you will see it listed in your back4app dashboard this project will be the foundation for all backend configurations discussed in this tutorial connect the parse sdk back4app relies on the parse platform to manage your data, provide real time features, handle user authentication, and more connecting your blazor application to back4app involves installing the parse sdk for net and initializing it with the credentials from your back4app dashboard retrieve your parse keys in your back4app dashboard, navigate to your app’s “app settings” or “security & keys” section to find your application id and net key you will also find the parse server url (often in the format https //parseapi back4app com ) install the parse sdk in your blazor project dotnet add package parse initialize parse in your blazor application typically, you would set up initialization in the program cs or a dedicated service class program cs using parse; var builder = webapplication createbuilder(args); // initialize parse parseclient initialize(new parseclient configuration { applicationid = "your application id", windowskey = "your dotnet key", server = "https //parseapi back4app com" }); var app = builder build(); // rest of your configuration this configuration ensures that whenever you use parse in your blazor application, it is pre configured to connect to your specific back4app instance by completing this step, you have established a secure connection between your blazor frontend and the back4app backend, paving the way to perform database operations, user management, and more step 2 – setting up the database saving and querying data with your back4app project set up and the parse sdk integrated into your blazor app, you can now start saving and retrieving data the simplest way to create a record is to use the parseobject class somedataservice cs using parse; using system threading tasks; public class somedataservice { public async task\<parseobject> createtodoitemasync(string title, bool iscompleted) { var todo = new parseobject("todo"); todo\["title"] = title; todo\["iscompleted"] = iscompleted; try { await todo saveasync(); console writeline("todo saved successfully " + todo objectid); return todo; } catch (exception ex) { console writeline("error saving todo " + ex message); return null; } } public async task\<ilist\<parseobject>> fetchtodosasync() { var query = new parsequery\<parseobject>("todo"); try { var results = await query findasync(); console writeline("fetched todo items " + results count); return results; } catch (exception ex) { console writeline("error fetching todos " + ex message); return null; } } } alternatively, you can use back4app’s rest api endpoints for operations schema design and data types by default, parse allows schema creation on the fly , but you can also define your classes and data types in the back4app dashboard for more control navigate to the “database” section in your back4app dashboard create a new class (e g , “todo”) and add relevant columns, such as title (string) and iscompleted (boolean) back4app also supports various data types string , number , boolean , object , date , file , pointer, array, relation , geopoint , and polygon you can choose the appropriate type for each field if you prefer, you can also let parse automatically create these columns when you first save an object from your blazor app back4app offers an ai agent that can help you design your data model open the ai agent from your app dashboard or on the menu describe your data model in simple language (e g , “please, create a new todo app at back4app with a complete class schema ”) let the ai agent create the schema for you using the ai agent can save you time when setting up your data architecture and ensure consistency across your application relational data if you have relational data for example, a category object that points to multiple todo items you can use pointers or relations in parse the process is similar to reactjs but using net objects somedataservice cs (continuation) public async task\<parseobject> createtaskforcategoryasync(string categoryobjectid, string title) { var todo = new parseobject("todo"); // create a pointer to the category var categorypointer = parseobject createwithoutdata("category", categoryobjectid); todo\["title"] = title; todo\["category"] = categorypointer; try { await todo saveasync(); return todo; } catch (exception ex) { console writeline("error creating task with category relationship " + ex message); return null; } } when querying, include pointer data somedataservice cs (continuation) public async task\<ilist\<parseobject>> fetchtodoswithcategoryasync() { var query = new parsequery\<parseobject>("todo") include("category"); try { var todoswithcategory = await query findasync(); return todoswithcategory; } catch (exception ex) { console writeline("error fetching todos with category " + ex message); return null; } } live queries for real time updates in a blazor server app, consider using signalr connection for live queries although the parse net sdk supports live queries, integrating them directly within a blazor application may require additional setup with signalr for real time communication enable live queries in your back4app dashboard under your app’s server settings make sure “live queries” is turned on configure live query client in net if needed however, for blazor apps, leveraging signalr might be more idiomatic for server side connections due to the complexity of setting up live queries within blazor and potential limitations of the parse net sdk in blazor webassembly, you may need to implement a server side service that bridges parse live queries with signalr clients step 3 – applying security with acls and clps back4app security mechanism back4app takes security seriously by providing access control lists (acls) and class level permissions (clps) these features let you restrict who can read or write data on a per object or per class basis, ensuring only authorized users can modify your data access control lists (acls) an acl is applied to individual objects to determine which users, roles, or the public can perform read/write operations for example somedataservice cs (acl example) public async task\<parseobject> createprivatetodoasync(string title, parseuser owneruser) { var todo = new parseobject("todo"); todo\["title"] = title; // create an acl granting read/write access only to the owner var acl = new parseacl(owneruser); acl publicreadaccess = false; acl publicwriteaccess = false; todo acl = acl; try { await todo saveasync(); return todo; } catch (exception ex) { console writeline("error saving private todo " + ex message); return null; } } when you save the object, it has an acl that prevents anyone but the specified user from reading or modifying it class level permissions (clps) clps govern an entire class’s default permissions, such as whether the class is publicly readable or writable, or if only certain roles can access it go to your back4app dashboard , select your app, and open the database section select a class (e g , “todo”) open the class level permissions tab configure your defaults, such as “requires authentication” for read or write, or “no access” for the public these permissions set the baseline, while acls fine tune permissions for individual objects a robust security model typically combines both clps (broad restrictions) and acls (fine grained per object restrictions) for more information go to app security guidelines https //www back4app com/docs/security/parse security step 4 – writing and deploying cloud functions cloud code is a feature of the parse server environment that allows you to run custom javascript code on the server side without needing to manage your servers or infrastructure by writing cloud code, you can extend your back4app backend with additional business logic, validations, triggers, and integrations that run securely and efficiently on the parse server how it works when you write cloud code, you typically place your javascript functions, triggers, and any required npm modules in a main js (or app js ) file this file is then deployed to your back4app project, which is executed within the parse server environment since these functions and triggers run on the server, you can trust them to handle confidential logic, process sensitive data, or make backend only api calls processes you might not want to expose directly to the client all cloud code for your back4app app runs inside the parse server that is managed by back4app, so you don’t have to worry about server maintenance, scaling, or provisioning whenever you update and deploy your main js file, the running parse server is updated with your latest code main js file structure a typical main js might contain require statements for any needed modules (npm packages, built in node modules, or other cloud code files) cloud function definitions using parse cloud define() triggers such as parse cloud beforesave() , parse cloud aftersave() , etc npm modules you installed (if needed) main js // main js // 1 import necessary modules and other cloud code files const axios = require('axios'); const report = require(' /reports'); // 2 define a custom cloud function parse cloud define('fetchexternaldata', async (request) => { const url = request params url; if (!url) { throw new error('url parameter is required'); } const response = await axios get(url); return response data; }); // 3 example of a beforesave trigger parse cloud beforesave('todo', (request) => { const todo = request object; if (!todo get('title')) { throw new error('todo must have a title'); } }); with the ability to install and use npm modules, cloud code becomes incredibly flexible, allowing you to integrate with external apis, perform data transformations, or execute complex server side logic typical use cases business logic for example, aggregate data for analytics or perform calculations before saving to the database data validations ensure certain fields are present or that a user has correct permissions before saving or deleting a record triggers perform actions when data changes (e g , send a notification when a user updates their profile) integrations connect with third party apis or services security enforcement validate and sanitize inputs to enforce security before performing sensitive operations deploy your function below is a simple cloud code function that calculates the length of a text string sent from the client main js // main js parse cloud define('calculatetextlength', async (request) => { const { text } = request params; if (!text) { throw new error('no text provided'); } return { length text length }; }); deploying via the back4app cli https //www back4app com/docs/local development/parse cli 1 install the cli for linux/macos curl https //raw\ githubusercontent com/back4app/parse cli/back4app/installer sh | sudo /bin/bash for windows download the b4a exe https //github com/back4app/parse cli/releases/download/release 3 3 1/b4a exe file from the releases page 2 configure your account key https //www back4app com/docs/local development/parse cli#f cxi b4a configure accountkey 3 deploy your cloud code b4a deploy deploying through the dashboard in your app’s dashboard, go to cloud code > functions copy/paste the function into the main js editor click deploy calling your function from blazor using the parse net sdk somedataservice cs (calling function) public async task\<int?> gettextlengthasync(string text) { try { var result = await parsecloud callfunctionasync\<dictionary\<string, object>>("calculatetextlength", new dictionary\<string, object> { { "text", text } }); if(result != null && result containskey("length")) return convert toint32(result\["length"]); return null; } catch(exception ex) { console writeline("error calling cloud function " + ex message); return null; } } you can also call it via rest or graphql as shown in the reactjs tutorial step 5 – configuring user authentication user authentication in back4app back4app leverages the parse user class as the foundation for authentication by default, parse handles password hashing, session tokens, and secure storage this means you don’t have to set up complex security flows manually setting up user authentication in a blazor application, you can create a new user with authservice cs using parse; using system threading tasks; public class authservice { public async task signupuserasync(string username, string password, string email) { var user = new parseuser() { username = username, password = password, email = email }; try { await user signupasync(); console writeline("user signed up successfully!"); } catch (exception ex) { console writeline("error signing up user " + ex message); } } public async task loginuserasync(string username, string password) { try { var user = await parseuser loginasync(username, password); console writeline("user logged in " + user username); } catch (exception ex) { console writeline("error logging in user " + ex message); } } } session management after a successful login, parse creates a session token that is stored in the user object in your blazor app, you can access the currently logged in user somecomponent razor cs var currentuser = parseuser currentuser; if (currentuser != null) { console writeline("currently logged in user " + currentuser username); } else { console writeline("no user is logged in"); } parse automatically handles token based sessions in the background, but you can also manually manage or revoke them for logging out authservice cs (logout) public async task logoutasync() { await parseuser logoutasync(); console writeline("user logged out"); } social login integration back4app and parse can integrate with popular oauth providers, such as google or facebook configuration may vary and often involves server side setup or additional packages refer to the social login docs https //www back4app com/docs/platform/sign in with apple for detailed instructions since blazor server apps run on asp net core, you might integrate social login using asp net core identity providers alongside parse for seamless authentication email verification and password reset to enable email verification and password reset navigate to the email settings in your back4app dashboard enable email verification to ensure new users verify ownership of their email addresses configure the from address , email templates, and your custom domain if desired these features improve account security and user experience by validating user ownership of emails and providing a secure password recovery method step 6 – handling file storage uploading and retrieving files parse includes the parsefile class for handling file uploads, which back4app stores securely fileservice cs using parse; using system; using system threading tasks; public class fileservice { public async task\<string> uploadimageasync(byte\[] filedata, string filename) { var parsefile = new parsefile(filename, filedata); try { await parsefile saveasync(); console writeline("file saved " + parsefile url); return parsefile url; } catch (exception ex) { console writeline("error uploading file " + ex message); return null; } } } to attach the file to an object fileservice cs (continued) public async task\<parseobject> createphotoobjectasync(byte\[] filedata, string filename) { var photo = new parseobject("photo"); var parsefile = new parsefile(filename, filedata); photo\["imagefile"] = parsefile; try { await photo saveasync(); return photo; } catch (exception ex) { console writeline("error creating photo object " + ex message); return null; } } retrieving the file url somecomponent razor cs var imagefile = photo get\<parsefile>("imagefile"); var imageurl = imagefile url; you can display this imageurl in your blazor components by setting it as the source of an \<img> tag file security parse server provides flexible configurations to manage file upload security use acls on parsefiles or set server level configurations as needed step 7 – scheduling tasks with cloud jobs cloud jobs cloud jobs in back4app let you schedule and run routine tasks on your backend like cleaning up old data or sending a daily summary email a typical cloud job might look like this main js parse cloud job('cleanupoldtodos', async (request) => { const todo = parse object extend('todo'); const query = new parse query(todo); const now = new date(); const thirty days = 30 24 60 60 1000; const cutoff = new date(now thirty days); query lessthan('createdat', cutoff); try { const oldtodos = await query find({ usemasterkey true }); await parse object destroyall(oldtodos, { usemasterkey true }); return `deleted ${oldtodos length} old todos `; } catch (err) { throw new error('error during cleanup ' + err message); } }); deploy your cloud code with the new job (via cli or the dashboard) go to the back4app dashboard > app settings > server settings > background jobs schedule the job to run daily or at whatever interval suits your needs cloud jobs enable you to automate background maintenance or other periodic processes without requiring manual intervention step 8 – integrating webhooks webhooks allow your back4app app to send http requests to an external service whenever certain events occur this is powerful for integrating with third party systems like payment gateways, email marketing tools, or analytics platforms navigate to the webhooks configuration in your back4app dashboard > more > webhooks and then click on add webhook set up an endpoint (e g , https //your external service com/webhook endpoint https //your external service com/webhook endpoint ) configure triggers to specify which events in your back4app classes or cloud code functions will fire the webhook for instance, if you want to notify a slack channel whenever a new todo is created create a slack app that accepts incoming webhooks copy the slack webhook url in your back4app dashboard, set the endpoint to that slack url for the event “new record in the todo class ” you can also add custom http headers or payloads if needed you can also define webhooks in cloud code by making custom http requests in triggers like beforesave, aftersave step 9 – exploring the back4app admin panel the back4app admin app is a web based management interface designed for non technical users to perform crud operations and handle routine data tasks without writing any code it provides a model centric , user friendly interface that streamlines database administration, custom data management, and enterprise level operations enabling the admin app enable it by going to app dashboard > more > admin app and clicking on the “enable admin app” button create a first admin user (username/password), which automatically generates a new role (b4aadminuser) and classes (b4asetting, b4amenuitem, and b4acustomfield) in your app’s schema choose a subdomain for accessing the admin interface and complete the setup log in using the admin credentials you created to access your new admin app dashboard once enabled, the back4app admin app makes it easy to view, edit, or remove records from your database without requiring direct use of the parse dashboard or backend code conclusion by following this comprehensive tutorial, you have created a secure backend for a blazor app on back4app configured a database with class schemas, data types, and relationships integrated real time queries where applicable for immediate data updates applied security measures using acls and clps to protect and manage data access implemented cloud code functions to run custom business logic on the server side set up user authentication with support for email verification and password resets managed file uploads and retrieval, with optional file security controls scheduled cloud jobs for automated background tasks used webhooks to integrate with external services explored the back4app admin panel for data management with a solid blazor frontend and a robust back4app backend, you are now well equipped to develop feature rich, scalable, and secure web applications continue exploring more advanced functionalities, integrate your business logic, and harness the power of back4app to save you countless hours in server and database administration happy coding! next steps build a production ready blazor app by extending this backend to handle more complex data models, caching strategies, and performance optimizations integrate advanced features such as specialized authentication flows, role based access control, or external apis check out back4app’s official documentation for deeper dives into advanced security, performance tuning, and logs analysis explore other tutorials on real time chat applications, iot dashboards, or location based services combine the techniques learned here with third party apis to create complex, real world applications