In this guide, we’ll be using Azure Functions in C# to upload a file to Azure Blob Storage.
Pre-requisites
- Azure blob storage connection string
- Packages:
- Microsoft.Azure.WebJobs
- Microsoft.Azure.Webjobs.Extensions.Storage
- Microsoft.NET.Sdk.Functions
Azure Function
Create your Azure Function and use an HTTP Trigger.
using System;
using System.IO;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Microsoft.Azure.Storage.Blob;
using Microsoft.Extensions.Configuration;
using Blobs.Logic;
namespace Blobs.Functions
{
public static class UploadBlob
{
[FunctionName("upload")]
public static async Task<IActionResult> Run(
[HttpTrigger(AuthorizationLevel.Function, "post", Route = null)] HttpRequest req,
ILogger log, ExecutionContext context)
{
try
{
var formdata = await req.ReadFormAsync();
bool isFileMissing = (req.Form.Files.Count == 0 && req.Form.Files["file"] == null);
string containerName = "my-container";
if (isFileMissing)
{
return new BadRequestObjectResult("The following parameters are required: 'file'");
}
string filename = formdata["filename"];
IFormFile file = req.Form.Files["file"];
string connectionString = GetConnectionString(context);
BlobStorage blobStorage = new BlobStorage(connectionString, containerName);
blobStorage.Initialize();
CloudBlockBlob blob;
blob = await blobStorage.CreateBlob(file, filename);
if (blob != null)
{
// Return url of created blob
string blobUrl = blob.Uri.ToString();
return new OkObjectResult(blobUrl);
}
else
{
return new BadRequestObjectResult("Failed to create blob.");
}
}
catch (ArgumentNullException ex)
{
return new UnprocessableEntityObjectResult(ex.Message);
}
catch (NullReferenceException ex)
{
return new UnprocessableEntityObjectResult(ex.Message);
}
catch (Exception ex)
{
if (String.IsNullOrEmpty(ex.Message))
{
return new BadRequestObjectResult("UnsupportedMediaType. Content type must be form-data");
}
else
{
return new UnprocessableEntityObjectResult(ex.Message);
}
}
}
private static string GetConnectionString(ExecutionContext executionContext)
{
var config = new ConfigurationBuilder()
.SetBasePath(executionContext.FunctionAppDirectory)
.AddJsonFile("local.settings.json", true, true)
.AddEnvironmentVariables().Build();
string connectionString = config["AzureWebJobsStorage"];
return connectionString;
}
}
}
BlobStorage.cs
using System;
using System.IO;
using System.Threading.Tasks;
using System.Linq;
using Microsoft.AspNetCore.Http;
using Microsoft.Azure.Storage;
using Microsoft.Azure.Storage.Blob;
using System.Collections.Generic;
using System.Net;
namespace Blobs.Logic
{
class BlobStorage
{
CloudStorageAccount StorageAccount {
get {
if(!String.IsNullOrEmpty(ConnectionString)) {
return CloudStorageAccount.Parse(ConnectionString);
}
else {
return null;
}
}
}
CloudBlobClient BlobClient
{
get
{
if (this.StorageAccount != null)
{
return this.StorageAccount.CreateCloudBlobClient();
}
else
{
return null;
}
}
}
private string ConnectionString;
private string ContainerName;
public BlobStorage(string _connectionString, string _containerName)
{
if (String.IsNullOrEmpty(_connectionString))
{
throw new ArgumentNullException("_connectionString is required");
}
else if (String.IsNullOrEmpty(_containerName))
{
throw new ArgumentNullException("_containerName is required");
}
this.ConnectionString = _connectionString;
this.ContainerName = _containerName;
}
public void Initialize()
{
if (this.StorageAccount == null)
{
throw new NullReferenceException("Error accessing Storage Account. Connection string might be invalid.");
}
this.CreateContainerIfNotExists();
}
CloudBlobContainer Container
{
get
{
CloudBlobContainer container = null;
if (this.BlobClient != null && !String.IsNullOrEmpty(this.ContainerName))
{
container = this.BlobClient.GetContainerReference(this.ContainerName);
}
return container;
}
}
public async Task<CloudBlockBlob> CreateBlob(IFormFile _file, string _fileName)
{
CloudBlobContainer container = this.Container;
string fileName = _fileName;
if(container != null)
{
if (String.IsNullOrEmpty(Path.GetFileNameWithoutExtension(fileName)))
{
if (String.IsNullOrEmpty(fileName))
{
fileName = "";
}
fileName += Guid.NewGuid().ToString();
}
string extension = Path.GetExtension(_file.FileName);
string blobName = $"{fileName}{extension}";
CloudBlockBlob blob = container.GetBlockBlobReference(blobName);
using (Stream stream = _file.OpenReadStream())
{
try
{
blob.Properties.ContentType = _file.ContentType;
await blob.UploadFromStreamAsync(stream).ConfigureAwait(false);
} catch
{
throw new ArgumentNullException("Failed to upload file, ContentType is not defined.");
}
}
return blob;
}
return null;
}
private void CreateContainerIfNotExists()
{
CloudStorageAccount storageAccount = this.StorageAccount;
if(storageAccount != null)
{
CloudBlobClient blobClient = this.BlobClient;
if(blobClient != null)
{
CloudBlobContainer blobContainer = blobClient.GetContainerReference(this.ContainerName);
blobContainer.CreateIfNotExistsAsync();
// Create a permission policy to set the public access setting for the container.
BlobContainerPermissions containerPermissions = new BlobContainerPermissions();
containerPermissions.PublicAccess = BlobContainerPublicAccessType.Blob;
//Set the permission policy on the container.
blobContainer.SetPermissions(containerPermissions);
}
}
}
}
}
To call the function locally
- Open postman, add a new POST request to
http://localhost:7071/api/upload. - Add form-data body.
-
To send a file from postman, hover on the Key column and select File on the dropdown, you should now see the “Select Files” button on the value column.
- You can add the filename field if you want to set the filename, this will be automatically generated if left blank.
- Send the request.
- You will receive the link for the created blob if the request was successful.
