How do I deploy .NET core Web API to Azure App Service?

Deploying a .NET Core Web API to Azure App Service is a streamlined process that enables you to host your application in a scalable and reliable cloud environment. The most common and user-friendly method involves using Visual Studio's built-in publishing tools.

How do I deploy .NET Core Web API to Azure App Service?

You can deploy your .NET Core Web API to Azure App Service primarily through Visual Studio's Publish feature, providing a direct and efficient pathway from your development environment to the cloud. Other methods include using Azure CLI, Azure DevOps pipelines, or Git deployments for more automated workflows.

Prerequisites for Deployment

Before you begin, ensure you have the following in place:

Azure Account: An active Azure subscription.
Visual Studio: Visual Studio 2019 or later, with the "Azure development" workload installed.
.NET Core SDK: The appropriate .NET Core SDK installed for your project version.
Developed Web API: A functional .NET Core Web API project.

Step-by-Step Deployment Using Visual Studio

The Visual Studio publishing wizard offers an intuitive way to deploy your API directly to Azure App Service.

Initiate the Publish Process:
- In Solution Explorer, right-click on your .NET Core Web API project.
- Select the Publish option from the context menu.
Choose Your Publish Target:
- In the Publish dialog that appears, select Azure as your publish target.
- Click the Next button to proceed.
Select Azure App Service (Windows):
- From the specific Azure service options, choose Azure App Service (Windows). This is the common choice for hosting .NET applications.
- Click Next.
Create a New Azure App Service Instance:
- You will be prompted to either select an existing App Service instance or Create a new Azure App Service. Choose the latter to provision new resources.
- If prompted, sign in to your Azure account.
Configure Your New App Service:
- A dialog box will appear to configure your new App Service instance. You'll need to provide the following details:
  - Name: A globally unique name for your App Service (e.g., mywebapi-demo).
  - Resource Group: Choose an existing resource group or create a new one. A resource group is a logical container for your Azure resources.
  - Hosting Plan: Select an existing App Service Plan or create a new one. The hosting plan defines the region, features, cost, and compute resources for your app. For most APIs, a Basic (B1) or Standard (S1) plan is a good starting point.
  - Region: Select the Azure region closest to your users for optimal performance.
Create the App Service:
- After configuring the settings, click the Create button.
- Visual Studio will provision the necessary resources in Azure. This may take a few moments.
Publish Your API:
- Once the App Service is created, Visual Studio will present a summary of the publish profile.
- Click the Publish button to deploy your .NET Core Web API to the newly created Azure App Service.
- Visual Studio will build your project, package it, and upload it to Azure. You can monitor the progress in the Output window.

Post-Deployment Steps and Best Practices

After successful deployment, consider these important steps:

Test Your API Endpoints: Navigate to the URL of your App Service (e.g., https://mywebapi-demo.azurewebsites.net/swagger if you use Swagger) and test your API endpoints to ensure they are functioning correctly.
Configure Application Settings: Manage your API's configuration, such as database connection strings, API keys, or environment-specific variables, within the Azure Portal under your App Service's "Configuration" section. These settings override values in appsettings.json.
- Example: To add a connection string, go to your App Service in the Azure Portal > Configuration > Application settings > New application setting.
Monitor Performance: Integrate Azure Application Insights to monitor your API's performance, track requests, and diagnose issues.
- You can enable Application Insights directly from the Azure Portal for your App Service.
Secure Your API: Implement proper authentication and authorization (e.g., Azure AD, OAuth 2.0) to protect your API endpoints. Consider enabling SSL/TLS (enabled by default for Azure App Services) and configuring CORS policies if needed.
Scaling: Adjust your App Service Plan to scale your API horizontally (instance count) or vertically (plan tier) based on demand.
Deployment Slots: For zero-downtime deployments and testing in production-like environments, utilize deployment slots. You can deploy to a staging slot, test it, and then swap it into production.

Alternative Deployment Methods

While Visual Studio publishing is excellent for initial deployments and quick updates, other methods offer more robust automation:

Method	Description	Ideal Use Case
Azure CLI	Command-line interface for managing Azure resources. You can deploy pre-built packages or publish directly from a Git repository using `az webapp deployment source config zip` or `az webapp up`.	Scripting, automation, local development environments.
Azure DevOps	Provides continuous integration and continuous deployment (CI/CD) pipelines. You can define build and release pipelines to automatically deploy your API whenever code changes are pushed to your repository.	Automated, enterprise-grade deployments, CI/CD workflows.
GitHub Actions	Similar to Azure DevOps, GitHub Actions allows you to create CI/CD workflows directly within your GitHub repository to build, test, and deploy your .NET Core Web API to Azure App Service.	Projects hosted on GitHub, streamlined CI/CD.
FTP/S	Direct file transfer protocol for uploading application files. While possible, it's generally not recommended for production environments due to lack of automation and potential for errors.	Quick, manual updates for small changes, troubleshooting.

For continuous integration and deployment, integrating with Azure DevOps or GitHub Actions is highly recommended, as they automate the entire process from code commit to deployment, ensuring consistency and reducing manual errors.