I'm going through the tutorials by AWS Mobile SDK - Xamarin Developer Guide and I want to upload a text file from my Android phone (through Xamarin) to AWS S3. These are the 2 tutorials: [Setting Up the AWS Mobile SDK for .NET and Xamarin](https://docs.aws.amazon.com/mobile/sdkforxamarin/developerguide/setup.html) and [Store and Retrieve Files with Amazon S3](https://docs.aws.amazon.com/mobile/sdkforxamarin/developerguide/getting-started-store-retrieve-s3-transferutility.html). 

I'm using the method `void Amazon.S3.Transfer.TransferUtility.Upload(string,string,string)` to upload my text file. I tried running my code but I couldn't. I run into this exception `**System.MissingMethodException:** 'Method not found: void Amazon.S3.Transfer.TransferUtility.Upload(string,string,string)'` despite the fact that I have included the correct namespaces. I have confirmed that the method `void Amazon.S3.Transfer.TransferUtility.Upload(string,string,string)` is found in the `namespace Amazon.S3.Transfer`. Below is my code

```
client = new AmazonS3Client(credentials, bucketRegion);
var fileTransferUtility = new TransferUtility(client);
fileTransferUtility.Upload(_fileName, bucketName, "toDo.txt");

```

I've included the correct namespaces, such as `using Amazon.S3;` `using Amazon.S3.Transfer;`

The above code works for Windows Presentation Foundation (WPF) Application, but not on Xamarin.

I've add the latest version of 

* AWSSDK.Core (v3.3.107.8)
* AWSSDK.S3 (v3.3.111.9)

How do I resolve this error? 

Any help is highly appreciated. Thank you so much in advance.