File Upload Service

FileUploadService.cs

/// <summary>
/// Generates a presigned URL of the file if it is successfully uploaded to S3
/// </summary>
/// <param name="file">File to be Uploaded</param>
/// <returns></returns>
public async Task<string> GetS3ObjectPresignedUrl(IFormFile file)
{
	try
	{
		var key = Path.GetRandomFileName() + Guid.NewGuid().ToString() + Path.GetExtension(file.FileName).ToLowerInvariant();
		
		if (await UploadFileToS3(file, key))
		{
			var getUrlRequest = new GetPreSignedUrlRequest
			{
				BucketName = BucketName,
				Key = key,
				Expires = DateTime.UtcNow.AddHours(ExpirationDurationInHours),
			};
			return _client.GetPreSignedURL(getUrlRequest);
		}
		return null;
	}
	catch (AmazonS3Exception e)
	{
		throw;
	}
	catch (Exception e)
	{
		throw;
	}
}


/// <summary>
/// Uploads the file to S3 Bucket if it exists
/// </summary>
/// <param name="file">Uploaded File</param>
/// <param name="key">Object Key for S3</param>
/// <returns></returns>
private async Task<bool> UploadFileToS3(IFormFile file, string key)
{
	try
	{
		if (await AmazonS3Util.DoesS3BucketExistV2Async(_client, BucketName))
		{
			var transferUtilityConfig = new TransferUtilityConfig
			{
				ConcurrentServiceRequests = 5,
				MinSizeBeforePartUpload = 20 * MB,
			};

			using (var transferUtility = new TransferUtility(_client, transferUtilityConfig))
			{
				var uploadRequest = new TransferUtilityUploadRequest
				{
					Key = key,
					BucketName = BucketName,
					InputStream = file.OpenReadStream(),
					PartSize = 20 * MB,
					StorageClass = S3StorageClass.Standard,
					ServerSideEncryptionMethod = ServerSideEncryptionMethod.AES256,
				};
				await transferUtility.UploadAsync(uploadRequest);
			}
			return true;
		}
		else
		{
			return false;
		}

	}
	catch (Exception e)
	{
		throw;
	}
}