Saving images in Azure Blob Storage using Lightswitch 2012

Question

I have a lightswitch application which currently stores all data in SQL Azure - including images. But I would like to keep the images separately in Azure Blob Storage and all non-binary data as it is.

So the outcome of saving an entity in the lightswitch app should be as follows: insert/update data SQL Azure and insert/update images to blob storage.

Any suggestion on the best approach on issue this would be greatly appreciated :).

Answer 1

I've added a short code to the server side of the LightSwitch application to save the images to Azure Blobs on add and update of the related data entry.

namespace LightSwitchApplication
{
    public partial class ApplicationDataService
    {
        string storageAccount = [aZURE_STORAGE_NAME_HERE]
        string containerName = [CONTAINTER_NAME_HERE]
        string policyName = [POLICY_NAME_HERE]
        string policySig = [OBTAINED_POLICY_SIG_HERE]

        partial void SaveChanges_Executing()
        {
            if (this.DataWorkspace.ApplicationData.Details.HasChanges)
            {
                EntityChangeSet changeSet = this.DataWorkspace.ApplicationData.Details.GetChanges();
                foreach (IEntityObject entity in changeSet.ModifiedEntities)
                {
                    string type = entity.GetType().Name;
                    // ... 
                    // My type of LightSwitch entities are for example "Places"

                    UploadFileToBlob((Place)entity, containerName, policyName, policySig);
                }
            }
        }

        private void UploadFileToBlob(Place p, String container, String policyName, String policySig)
        {
            string signature = "?sr=c&si=" + policyName + "&sig=" + policySig;
            string file = p.Id + ".png";
            WebResponse resp = UploadFile(storageAccount, container, file, signature, p.Photo);
        }

        static WebResponse UploadFile(string storageAccount, string container, string filename, string signature, byte[] data)
        {
            try
            {
                var req = (HttpWebRequest)WebRequest.Create(string.Format("http://{0}.blob.core.windows.net/{1}/{2}{3}", storageAccount, container, filename, signature));
                req.Method = "PUT";
                req.ContentType = "image/png";
                req.ContentLength = data.Length;
                req.Date = DateTime.UtcNow;
                //req.Headers.Add("x-ms-date", DateTime.UtcNow.ToString());
                req.Headers.Add("x-ms-version", "2012-02-12");
                req.Headers.Add("x-ms-blob-type", "BlockBlob");

                using (Stream stream = req.GetRequestStream())
                {
                    stream.Write(data, 0, data.Length);
                }

                var a = req.Headers.ToString();

                return req.GetResponse();
            }
            catch (Exception e)
            { 
                // ...
            }
        }
    }
}

What it does it sends the file to the blob any-time the corresponding entity is changed. Values in the square brackets need to be change in accordance to your Azure account.

The method of obtaining policy signature is a Shared Access Signature well described in official documentation: Part 1 & Part 2.