...
<PMode xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns="eu:edelivery:as4:pmode">
<MessageHandling>
<Deliver>
<IsEnabled>true</IsEnabled>
<PayloadReferenceMethod>
<Type>BLOB</Type>
<Parameters>
<Parameter name="ConnectionString" value="" />
<Parameter name="Container" value="" />
</Parameters>
</PayloadReferenceMethod>
</Deliver>
</MessageHandling>
</PMode># Uploading Payloads to a Custom Location
When a message must be delivered, it can contain payloads. The <b>AS4.NET</b> component can deliver payloads to some predefined locations (filesystem, payloadservice) and can be extended to upload payloads to custom locations.
Each uploader must implement following interface:
```csharp
/// <summary>
/// Interface to upload Payloads to a given Media
/// </summary>
public interface IAttachmentUploader
{
...
void Configure(Method payloadReferenceMethod);
...
Task<UploadResult> UploadAsync(Attachment attachment, UserMessage referringUserMessage);
}
```
Since the **Deliver Message** references the location of the uploaded payloads, the uploader returns an **Upload Result**. This contains a reference and an id that can be included in the **Deliver Message**.
Each uploader can be configured with settings that can be found in the **Receiving PMode**:
```xml
...
<MessageHandling>
<Deliver>
<IsEnabled>true</IsEnabled>
<PayloadReferenceMethod>
<Type>BLOB</Type>
<Parameters>
...
</Parameters>
</PayloadReferenceMethod>
</Deliver>
</MessageHandling>
</PMode>
```
If payloads have to be uploaded to **Azure Blob Storage**, an `IAttachmentUploader` can be implemented that looks like this:
```csharp
public class BlobAttachmentUploader : IAttachmentUploader
{
private CloudBlobContainer _container;
public void Configure(Method payloadReferenceMethod)
{
CloudStorageAccount storageAccount = CloudStorageAccount.Parse(
payloadReferenceMethod["ConnectionString"].Value);
CloudBlobClient client = storageAccount.CreateCloudBlobClient();
_container = client.GetContainerReference(payloadReferenceMethod["Container"].Value);
_container.CreateIfNotExists();
}
public async Task<UploadResult> UploadAsync(
Attachment attachment,
UserMessage referringUserMessage)
{
CloudBlockBlob blob = _container.GetBlockBlobReference(attachment.Id);
await blob.UploadFromStreamAsync(attachment.Content);
return UploadResult.SuccessWithIdAndUrl(
payloadId: blob.Name,
downloadUrl: blob.Uri.AbsolutePath
);
}
}
```
The `IAttachmentUploader` can return different types of `UploadResult`'s:
- `UploadResult.SuccessWithUrl(downloadUrl : string)` which means that the attachment is successfully uploaded and we get an download url where the attachment can be retrieved.
- `UploadResult.RetryableFail` which means that the attachment can't be uploaded but could succeed with another try. If the _Receiving Processing Mode_ is configured for retryable delivery, the uploading of the attachment will be retried.
- `UploadFatalFail` which means that the attachment can't be uploaded and will not be retried even if the _Receiving Processing Mode_ is configured this way.
#### Registration
To make sure that the <b>AS4.NET</b> component understands how to upload attachments to **Blob Storage**, we must register the custom `IAttachmentUploader` type in the `Registry`.
```csharp
Registry.Instance.AttachmentUploader.Accept(
condition: s => s == "BLOB",
uploader: new BlobAttachmentUploader());
```
This `"BLOB"` string will correspond with the Type configured in the **Receiving PMode**.
```xml
...
<MessageHandling>
<Deliver>
<IsEnabled>true</IsEnabled>
<PayloadReferenceMethod>
<Type>BLOB</Type>
<Parameters>
...
</Parameters>
</PayloadReferenceMethod>
</Deliver>
</MessageHandling>
</PMode>
```