Is it possible to delete the blob which triggers an azure function

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Is it possible to delete the blob which triggers an azure function

Peter Sharp 181

I've read around and it seems like people are doing this, but I just can't seem to get it to work.

how-to-delete-a-blob-using-azure-functions

cannot-delete-the-blob-that-triggers-an-azure-function-blob-input-binding

Can anyone provide me with guidance on having a blob trigger for a function, read that blob as a stream, and when finished, delete the triggering blob?

Many thanks

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Answer 1

MughundhanRaveendran-MSFT 12,506

@Peter Sharp ,

Thanks for reaching out to Q&A.

Yes, it appears that the deletion of the blob is possible via azure functions. You can read the blob as a stream by referring to this article : https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-storage-blob-input?tabs=csharp

You can delete the blob using the below code. You will have to add the nuget package namespace "using Azure.Storage.Blobs"

BlobClient client = new BlobClient("connectionString", "container", "blobName");
client.DeleteIfExists();

You might also find the blob receipts to be interesting.

I hope this helps!

Please 'Accept as answer' and ‘Upvote’ if it helped so that it can help others in the community looking for help on similar topics.

Peter Sharp 181 Reputation points

2021-11-04T01:10:50.347+00:00

Thanks for the response.

I've seen similar commentary around, but I still can't figure out how this applies to Azure Functions specifically.

Nuget seems to relate to the local development environment. Am I wrong with this? How is nuget applied to a Function?

For reference, I am developing in the Function Portal at the moment, so I don't have a local environment. I'm working up to it, but have been able to avoid it thus far.

And what, specifically, is 'connectionstring'? How can I use that securely? Can I use the connection details already in use by my bindings? If so, how?

I am new to Functions (clearly), but I'm finding the directions on how to implement things like this extremely confusing.

Any help you could offer would be greatly appreciated.

Thanks
Peter Sharp 181 Reputation points

2021-11-04T01:34:32.55+00:00
Answered myself on the connection string.

The bindings use connection strings stored in Application Settings under configuration. These are exposed as environment variables in the script.

So if my Storage Account Connection (as referred to by bindings in Integration) is called 'AzureWebJobsStorage', we can get it in script with:

var storageConnectionString = System.Environment.GetEnvironmentVariable("AzureWebJobsStorage");

I'm starting to get a handle on nuget (I think). I might be off the mark, but it seems that I might need to switch to using Visual Studio, create a file named 'function.proj', and put the nuget references in there. Uploading it then should trigger nuget behind my Function server for me. I think.

This all seems way too obscure. Nuget packages should be surfaced somewhere in the portal IMO.

Thanks for any other insight you can offer.
MughundhanRaveendran-MSFT 12,506 Reputation points

2021-11-05T07:36:36.757+00:00

@Peter Sharp , Please refer to this article to add nuget packages to the Functions for portal development : https://stackoverflow.com/questions/36411536/how-can-i-use-nuget-packages-in-my-azure-functions

However I would recommend using Visual Studio for the complete development of Functions as its a proper IDE. You wont be able to debug the code in the portal however debugging, adding dependencies, adding nuget pacakges are very easy in Visual Studio. Once you develop in Visual Studio, you can test the function by running it locally and then publish it to the Azure functions from Visual Studio
Peter Sharp 181 Reputation points

2021-11-08T06:46:32.707+00:00

Thanks for touching base again.

I originally tried to follow the steps to develop locally, but I got lost along the way with things not working. The browser editor was there and seemed viable, so I went that route. But the lack of functionality was a drag (proper code insight, IntelliSense, debugging, etc.).

Since posting this, I tried to give VSCode a swing, and it seemed really good (in that it seemed familiar to the browser editor I had become used to), but I just couldn't get it to compile and deploy. Dependencies were not working and overall, it was just a flop.

Visual Studio, on the other hand, worked fine for me as soon as I let go of the idea of using what I'd already built as a template. From the Function App, I found you can download the entire app content as a zip file, complete with Visual Studio Project. When you do this for an app developed in the browser, you get a run.csx and function.json per function, but I couldn't get anything with any kind of dependencies to compile.

Oddly, the download functionality has no apparent purpose if you're publishing from Visual Studio, as it just downloads the DLL and generated function.json files.

But if you start a Function App from scratch, and copy the content from your run.csx file into the boilerplate code in the cs file (with special attention to the bindings), then you at least have a chance to get things working.

In the end, I did get this working, and it was surprisingly easy once nuget started playing ball.

Your feedback was helpful, so thanks.

Answer 2

In case it helps anyone, here is how I did it.

Develop locally using Visual Studio (or alternative if you can make it work). The instructions in 'Function App > Overview > Quickstart > Start with a code editor' work.

Use Nuget Package Manager (Tools > Nuget Package Manager > Manage NuGet Packages for Solution) and update 'Microsoft.Azure.WebJobs.Storage' to version 5.0.0.

This has Azure.Storage.Blobs as a dependency - and this version doesn't have the bug when prevents the initial version from building properly.

Leave Microsoft.NET.Sdk.Functions at 3.0.13 to stay with LTS version of .NET.

Then ...

using Azure.Storage.Blobs;

... and then ...

var storageConnectionString = System.Environment.GetEnvironmentVariable("AzureWebJobsStorage");

This loads the connection string from Application Settings.

From there, the following should just work.

                var client = new BlobClient(storageConnectionString, "test-path", "in/" + name);
                client.DeleteIfExists();

Hope this helps someone.

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Is it possible to delete the blob which triggers an azure function

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