Blobs

Function Monkey supports two approaches for responding to blob storage events:

1. Deserializing directly into a command from JSON - useful for small blobs who's format is known in advance
2. Assigning a stream to a command that can be picked up in the handler - useful for blobs who's format is not known or that are very large and require careful processing

Deserializing Directly Into a Command

First begin by creating an empty Azure Functions v2 project and then install the core nuget packages for Function Monkey:

Install-Package FunctionMonkey
Install-Package FunctionMonkey.Compiler

You will also need the extension package for the storage triggers (at the time of writing this is 3.0.0-beta8):

Install-Package Microsoft.Azure.WebJobs.Extensions.Storage

Now create a folder in the solution called commands and create a class called HelloWorldCommand:

public class HelloWorldCommand : ICommand
{
    public string UserName { get; set; }
}

Next create a folder in the solution called Handlers and create a class called HelloWorldCommandHandler:

internal class HelloWorldCommandHandler : ICommandHandler<HelloWorldCommand>
{
    public Task ExecuteAsync(HelloWorldCommand command)
    {
        Debug.WriteLine($"Hello {command.UserName}");
        return Task.CompletedTask;
    }
}

And now we'll create our function app configuration in the root of the project that registers the command handler and registers the command with a storage account and blob container:

public class FunctionAppConfiguration : IFunctionAppConfiguration
{
    private const string ContainerName = "myblobcontainer";
    private const string StorageConnectionName = "storageConnection";

    public void Build(IFunctionHostBuilder builder)
    {
        builder
            .Setup((serviceCollection, commandRegistry) =>
                commandRegistry.Register<HelloWorldCommandHandler>()
            )
            .Functions(functions => functions
                .Storage(StorageConnectionName, storage => storage
                    .BlobFunction<HelloWorldCommand>($"{ContainerName}/{name}")
                )
            );
    }
}

Finally we need to create an entry in local.settings.json for the Azure Storage connection string:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "AzureWebJobsDashboard": "UseDevelopmentStorage=true",
    "storageConnection": "<connection string>" 
  }
}

And that's it! If you run this sample you should find that adding a blob to the container triggers the function. Note that Azure Functions blob triggers do not work with the storage emulator, you need to use a real storage account.

Note that it is possible to omit the connection setting name - see default connection settings for more details.

Using Streams

First begin by creating an empty Azure Functions v2 project and then install the core nuget packages for Function Monkey:

Install-Package FunctionMonkey
Install-Package FunctionMonkey.Compiler

Now create a folder in the solution called commands and create a class called HelloWorldCommand - in addition to implementing the ICommand interface we also must implement the IStreamCommand:

public class HelloWorldCommand : ICommand, IStreamCommand
{
    public Stream Stream { get; set; }

    public string Name { get; set; }
}

Next create a folder in the solution called Handlers and create a class called HelloWorldCommandHandler:

internal class HelloWorldCommandHandler : ICommandHandler<HelloWorldCommand, Message>
{
    public Task<Message> ExecuteAsync(HelloWorldCommand command, Message previousResult)
    {
        using (StreamReader reader = new StreamReader(command.Stream))
        {
            string json = reader.ReadToEnd();
            return Task.FromResult(new Message
            {
                Text = $"JSON payload\n{json}"
            });
        }                
    }
}

Our handler will be provided an open stream to the blob in the Stream property and the name of the blob in the Name property of the command.

And now we'll create our function app configuration in the root of the project that registers the command handler and registers the command with a storage account and blob container:

public class FunctionAppConfiguration : IFunctionAppConfiguration
{
    private const string ContainerName = "myblobcontainer";
    private const string StorageConnectionName = "storageConnection";

    public void Build(IFunctionHostBuilder builder)
    {
        builder
            .Setup((serviceCollection, commandRegistry) =>
                commandRegistry.Register<HelloWorldCommandHandler>()
            )
            .Functions(functions => functions
                .Storage(StorageConnectionName, storage => storage
                    .BlobFunction<HelloWorldCommand>($"{ContainerName}/{name}")
                )
            );
    }
}

Finally we need to create an entry in local.settings.json for the Azure Storage connection string:

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "AzureWebJobsDashboard": "UseDevelopmentStorage=true",
    "storageConnection": "<connection string>" 
  }
}

And that's it! If you run this sample you should find that adding a blob to the container triggers the function and you're given an open stream. Note that Azure Functions blob triggers do not work with the storage emulator, you need to use a real storage account.