How to Process file on S3 event through AWS lambda using C#

I am looking for C# code blocks to read file from S3 on PUT event and upload the file to another bucket. I am fairly new to C# and see most of the blogs are either written for python and java. Any help will be highly appreciated.

Thanks,

I know it's too late but maybe this will help someone else.
You need to add Amazon.Lambda.S3Events Nuget package. See code, this is how your Lambda Function should look like:

<!-- language: csharp -->

using System;
using System.Threading.Tasks;
using Amazon.Lambda.Core;
using Amazon.Lambda.S3Events;
using Amazon.S3;
using Amazon.S3.Model;

public async Task<string> FunctionHandler(S3Event evnt, ILambdaContext context)
{
    var s3Event = evnt.Records?[0].S3;
    if(s3Event == null)
    {
        return null;
    }

    try
    {
        var destinationBucketName = "your_bucket_to_upload";
        var destinationKey= "folder/subfolder/fileName.txt";

        var s3 = new AmazonS3Client();
        var request = new CopyObjectRequest
        {
            SourceBucket = s3Event.Bucket.Name,
            SourceKey = s3Event.Object.Key,
            DestinationBucket = destinationBucketName,
            DestinationKey = destinationKey
        };
        
        var response = await s3.CopyObjectAsync(request);
        return response.HttpStatusCode.ToString();
    }
    catch(Exception e)
    {
        context.Logger.LogLine($"Error getting object {s3Event.Object.Key} from bucket {s3Event.Bucket.Name}. Make sure they exist and your bucket is in the same region as this function.");
        context.Logger.LogLine(e.Message);
        context.Logger.LogLine(e.StackTrace);
        throw;
    }
}

You can find AWS Toolkit for Visual Studio here:
https://docs.aws.amazon.com/lambda/latest/dg/csharp-package-toolkit.html

The flow would be:

• Configure an Amazon S3 Event to trigger the AWS Lambda function when a new object is created
• Details of the object created will be passed to the Lambda function via the event
• Your Lambda function should then call CopyObject() to duplicate the object to another bucket (no need to download/upload)

See also: Copying Objects - Amazon Simple Storage Service

Create a bucket and create IAM role that has access to the bucket you created. Assign to that role to your lambda function ( either thru AWS console or AWS SDK if you use Visual studio. the option is available in the following screenshot1)

After you published go to the Event Trigger tab and add the bucket you created. Make sure you upload the code again once you set this trigger

Upload a file and check from the cloud watch log to see function has executed. Some sample code is attached here