Is it possible to read File from same folder where Azure function exists

Question

In my Azure C# function I need to read a .txt file. I make the .txt file in Visual studio and set it to "copy Always".

Now I am using this code to read the file

var dir = System.IO.Path.GetDirectoryName(
    System.Reflection.Assembly.GetEntryAssembly().Location);

var path = System.IO.Path.Combine(dir, "twinkle.txt");

this code doesn't work. When I open the folder which is the value of dir. It lead me to this directory ""C:\Users{username}\AppData\Local\Azure.Functions.Cli\1.0.9""

How I can store a simple txt file in Azure function. Or I need Azure Storage for this.

Anything else I can do to get this done.

Update for showing file copied

Everyday

Embed that file as a resource into assembly. – Gouge

@Gouge I am checking that way, thanks for idea. – Everyday

@Gouge yes, it's working. thanks – Everyday

Answer 1

Here is how to get to the correct folder:

public static HttpResponseMessage Run(HttpRequestMessage req, ExecutionContext context)
{
    var path = System.IO.Path.Combine(context.FunctionDirectory, "twinkle.txt");
    // ...
}

This gets you to the folder with function.json file. If you need to get to bin folder, you probably need to go 1 level up, and then append bin:

// One level up
Path.GetFullPath(Path.Combine(context.FunctionDirectory, $"..{Path.DirectorySeparatorChar}twinkle.txt"))

// Bin folder
Path.GetFullPath(Path.Combine(context.FunctionDirectory, $"..{Path.DirectorySeparatorChar}bin{Path.DirectorySeparatorChar}twinkle.txt"))

Garnish

I don't believe I have access to ExecutionContext at startup. Any other way to do that? – Ursine

I had the same problem @BillNoel, I've posted an answer below that address the issue. – Maple

You can just add ExecutionContext context as a parameter to the Run method of your function. – Brunet

context.FunctionAppDirectory gives you access to anything in the applications root folder context.FunctionDirectory only gives you access to the function specific directory – Normy

This will only work on Windows (if it works) – Chaldea

context.FunctionAppDirectory is the right answer now. Adding this in the event somebody else lands here and gets confused. – Mab

Answer 2

For those like me who doesn't have access to ExecutionContext since we have to read a file in Startup.

var binDirectory = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
var rootDirectory = Path.GetFullPath(Path.Combine(binDirectory, ".."));

///then you can read the file as you would expect yew!
File.ReadAllText(rootDirectory + "/path/to/file.ext");

Also worth noting that Environment.CurrentDirectory might work on a local environment, but will not work when deployed to Azure.

Works inside functions too.

Reference

Maple

Super useful for including Google.json files that are necessary for FirebaseAdmin functions! Thanks, louie! – Ursine

Wondering how this has worked for everyone. The executing assembly directory that I see is a temporary ASP.NET location and the config file of course does not exists there. "D:\local\Temporary ASP.NET Files\root\80e1a0b8\1c033853\assembly\dl3\dc0956b6\". – Partner

Hmmm, that is strange indeed, it's maybe worth checking out the reference I included in the answer @PrasadKorhale – Maple

If I have the file in folder it doesn't work, it had to be directly places under root folder – Spermatophore

@PrasadKorhale, because I think you are deploying the source code (as opposed to a built assembly) and your project is being compiled on the hosting of Functions App. – Borneo

@Spermatophore then you have to navigate to the folder after getting the root directory similar to what I have in the answer rootDirectory + "/your/sub/folders/file.ext" – Maple

Needed to add "wwwroot" to the end for working. var rootDirectory = Path.Combine(Path.GetFullPath(Path.Combine(binDirectory, ".."),"wwwroot")); – Parang

Answer 3

To use a file called pub_key.pem in an Azure Function. I'd rather do this in the .csproj file:

<ItemGroup>
    <EmbeddedResource Include="pub_key.pem">
      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
    </EmbeddedResource>
</ItemGroup>
 

and then read the file using a Stream

var assy = Assembly.GetAssembly(typeof(AnyClassInFunction)); 
Stream fileStream = assy.GetManifestResourceStream(typeof(AnyClassInFunction),"pub_key.pem");

Vitale

Answer 4

I tried most of the above but still had issues. I found an article on another site where MS suggested a way to do this.

I ended up with an Environment Variable in local.settings.json that held the path to the dir containing my files.

Locally it was: "LiquidTemplatesPath": "C:_WorkingFolder_Code_Integrations_Partner"

In the AzFn Env it was: C:_home_site_wwwroot

This reflects the folder it sits in on the server. In code I then just access it as follows:

string? azure_root = Environment.GetEnvironmentVariable("LiquidTemplatesPath");
azure_root = azure_root.Replace("_", "/");
string liquidTemplate = File.ReadAllText($"{azure_root}{templateTxtPathWithLeadingSlash}");

The reason for _ in the variable is because I also hit issues trying to pass it in the YAML pipeline so this was the easiest workaround e.g.

          appSettings: 
            -LiquidTemplatesPath C:_home_site_wwwroot

Hopefully this might help someone.

Reunion

Answer 5

Here is a useful link: https://github.com/Azure/azure-functions-host/wiki/Retrieving-information-about-the-currently-running-function

There is the possibility of a hard coded way:

File.ReadAllText("d:\home\site\wwwroot\NameOfYourFunction" + "/path/to/file.ext");

Piperonal

This sound cool but hard coded code are bad. What if Azure suddenly storing Function somewhere else ? – Everyday