How To Upload Files Into Azure Blob Storage Using Azure Functions In C#

Open the local.settings.json file in our function app and paste the connection string of our Azure Storage resource as the value of the “AzureWebJobsStorage” key. Also, add another key called “ContainerName” and paste the name of the container we created earlier.

{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "<replace your blob storage connection key here>",
        "ContainerName": "file-upload", // Container name
        "FUNCTIONS_WORKER_RUNTIME": "dotnet"
    }
}

To interact with Azure storage, we have to first install the below NuGet package.

Now add the below code to upload a file into the container in our blob storage.

using Azure.Storage.Blobs;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Extensions.Logging;
using System;
using System.IO;
using System.Threading.Tasks;
namespace FileUploadFunction {
    public static class FileUpload {
        [FunctionName("FileUpload")]
        public static async Task < IActionResult > Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = null)] HttpRequest req, ILogger log) {
            string Connection = Environment.GetEnvironmentVariable("AzureWebJobsStorage");
            string containerName = Environment.GetEnvironmentVariable("ContainerName");
            Stream myBlob = new MemoryStream();
            var file = req.Form.Files["File"];
            myBlob = file.OpenReadStream();
            var blobClient = new BlobContainerClient(Connection, containerName);
            var blob = blobClient.GetBlobClient(file.FileName);
            await blob.UploadAsync(myBlob);
            return new OkObjectResult("file uploaded successfylly");
        }
    }
}

First, we have stored the Blob Storage connection string and container name from configuration into local variables. After that, we read the file request by using a key called “File” into the variable, and using the OpenReadStream() function, we read the file into the steam. To interact with Blob storage, we first have to create BlobContainerClient by passing the connection string and container name. After creating the client, we have to create BlobClient using the GetBlobClient method by passing the input file name.

Finally, to upload the file to the container, we used the UploadAsync method by passing the stream. You can read more about these methods here.

Now run the FileUpload function.

For testing the function, open Postman and paste the about function URL, i.e., http://localhost:7071/api/FileUpload

Now in our code, we have read the file from form data, so click on Body and select form-data, then add key as “File,” and for value, select which file you want to upload and click on Send button.

Now if we open our “file-upload” container, we can see the file that we uploaded.

Publish Azure function to Azure function app using Visual Studio

Create a function app using the Azure portal

Log in to the Azure portal. In the Search bar, search "function app" and then select the Function app.

After that, click on the " + Create" button to add a new function app. Fill out the basic details,

Now click on Review: Create button review all the details and click on the Create button. Wait for a few minutes to create the resources.

Once deployment is complete, click on the Go to Resource button to see our new function app.

Publish the azure function into the function app

To deploy our function to Azure, we need Azure Function App. Right-click on our solution and click on the Publish button.

As we are publishing into Azure, then Select Azure and click on Next. Select the target as "Azure Function App(Windows)" and click on Next. We can either select an already created function app or we can create a new Function app.

Click on the Finish button.

Click on Publish button to push our function to our Function App.

Once our app is successfully published on Azure, go to the Azure portal and search for our function app. Select Functions from the left sidebar to see our deployed function.

Configure the storage account connection string into Configuration setting of Function app

Now we have deployed our function into Function app so next step is to configure the settings. So click on Configuration. For this app we have to set value of Storage connection string and container name in configuration. So seach for "AzureWebJobsStorage" and click on Edit button and paste your storage connection string.

Click on "+ New application setting" and give name as "ContainerName" and Value as "file-upload".

Finally click on Save button to save changes.

Test publish app using postman

To ge the url of deployed function click on Functions -> Select File Upload function -> Click on Get Function Url -> Copy url and paste in postman.

Now as we test locally in form-data add a key "File" and select file you want to upload.

Now if we check container we can see the file uploaded into it.

Conclusion

In this article, we have discuss about Azure Storage and Azure blob storage. We have created a Azure Blob storage resource from Azure Portal. We created a new Azure function from Visual Studio which uploads the file to blob storage. Also, I demonstrated how to test and deploy the function from VS and test using Postman. I really hope that you enjoyed this article, share it with friends, and please do not hesitate to send me your thoughts or comments. Stay tuned for more Azure Functions articles.