How to Use AWS Lambda with .NET Core for Serverless Applications

Introduction

In modern cloud development, building scalable applications without managing servers has become a standard approach. This is where serverless computing comes into the picture.

AWS Lambda is one of the most popular serverless services that allows you to run code without provisioning or managing servers. When combined with .NET Core, developers can build powerful, scalable, and cost-effective applications using familiar C# skills.

In this article, we will understand how to use AWS Lambda with .NET Core step by step in simple words, along with practical examples and real-world scenarios.

What is AWS Lambda?

AWS Lambda is a serverless compute service provided by Amazon Web Services.

Simple understanding

Think of AWS Lambda as a function that runs only when needed.

You upload your code
AWS runs it automatically when triggered
You pay only for execution time

Key features

No server management
Automatic scaling
Pay-as-you-go pricing

What is .NET Core in Serverless?

.NET Core (now .NET) allows developers to build cross-platform applications using C#.

When used with AWS Lambda:

You write functions in C#
Deploy them to AWS
Trigger them using events like HTTP requests, file uploads, or database changes

Why Use AWS Lambda with .NET Core?

Benefits

Use existing C# skills
Build scalable APIs
Reduce infrastructure cost
Faster deployment cycles

Real-world example

Imagine a file upload system:

User uploads image to S3
Lambda function processes image
Saves result to database

No server is needed.

Prerequisites

Before starting, make sure you have:

AWS account
.NET SDK installed
Visual Studio or VS Code
AWS CLI configured

Step 1: Install AWS Lambda Tools for .NET

Install the required tools using CLI:

dotnet tool install -g Amazon.Lambda.Tools

This tool helps you create, build, and deploy Lambda functions.

Step 2: Create a New Lambda Project

Run the following command:

dotnet new lambda.EmptyFunction -n MyLambdaApp

This creates a basic AWS Lambda project.

Project structure

Function.cs → main logic
aws-lambda-tools-defaults.json → deployment settings

Step 3: Write Your Lambda Function

Example:

using System;
using Amazon.Lambda.Core;

[assembly: LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]

public class Function
{
    public string FunctionHandler(string input, ILambdaContext context)
    {
        return $"Hello {input}";
    }
}

What this does

Accepts input
Returns a response
Logs can be tracked using context

Step 4: Deploy Lambda Function to AWS

Run this command:

dotnet lambda deploy-function MyLambdaApp

What happens here

Code is packaged
Uploaded to AWS Lambda
Function is created in AWS

Step 5: Test the Lambda Function

You can test using AWS Console or CLI.

Example input:

"World"

Output:

"Hello World"

Step 6: Connect Lambda with API Gateway

To expose your Lambda as an API:

Go to AWS API Gateway
Create new API
Connect it to Lambda

Now your function can be accessed via HTTP endpoint.

Example: Simple Web API using Lambda

You can create an API that returns user data.

Request → GET /users
Lambda processes request
Returns JSON response

Step 7: Logging and Monitoring

AWS automatically integrates Lambda with CloudWatch.

What you can track

Logs
Execution time
Errors

Why it matters

Helps in debugging and performance tuning.

Step 8: Environment Variables

You can store configuration values in Lambda.

Example:

DB_CONNECTION
API_KEY

These can be accessed inside your code.

Step 9: Error Handling

Always handle errors properly.

Example:

try
{
    // logic
}
catch(Exception ex)
{
    context.Logger.LogLine(ex.Message);
    throw;
}

Best Practices

Keep functions small and focused
Use environment variables for configuration
Optimize cold start performance
Use logging for debugging

Advantages

No server management
Automatic scaling
Cost-efficient
Easy integration with AWS services

Disadvantages

Cold start latency
Limited execution time
Debugging can be tricky

Real-World Use Case

Consider an e-commerce platform:

User places order
Lambda processes order
Sends confirmation email

All without managing servers.

Summary

Using AWS Lambda with .NET Core allows developers to build scalable and efficient serverless applications with minimal infrastructure management. You can write functions in C#, deploy them easily, and integrate with other AWS services like API Gateway and S3. By following best practices and understanding the workflow, you can build production-ready serverless applications that are cost-effective and highly scalable.