Simple 7 steps to run your first Azure Blob Program

Simple 7 steps to run your first Azure Blob
Program

Introduction


Step 1:- Ensure you have
things at place

Step 2:-
What will we do?

Step 3:-
Create a web role


Step 4:- Set the blob
connection string



Step 5:- Create the blob
on webrole onstart



Step 6:- Code your ASP.NET UI


Step 7:- Run the project and enjoy

Introduction

In this section we will create our first program using Azure blobs. This article
creates a simple web page where we upload image files which are stored in azure
blobs. We have also created a simple search text box which will help us to
search the image blobs with the image file name.

In case you are a complete newbie to azure you can download my two azure basic
videos which explain what azure is all about Azure Faq Part 1 :-
Video1 , Azuer Faq Part 2 :-
Video2.

Please feel free to download my free 500 question and answer eBook which covers
.NET , ASP.NET , SQL Server , WCF , WPF , WWF@
http://www.questpond.com/ .

Step 1:- Ensure you have
things at place

In case you are a complete fresher to Azure,
please ensure you have all the pre-requisite at place. You can read the below
article to get the basic prerequisite

http://computerauthor.blogspot.com/2010/01/simple-5-steps-to-run-your-first-azure.html .

Step 2:-
What will we do?

Azure Blobs help to store large items like
files, in other words its file storage system. In this article we will create a
simple program to upload image files in Azure blob system.

Step 3:-
Create a web role

The first step is to a create a web role
project. In case you are fresher in Azure, you can go through

http://computerauthor.blogspot.com/2010/01/simple-5-steps-to-run-your-first-azure.html to understand
how to create a web role project.
So let’s create a simple project with name ‘BlobStorage’. Once you have created
the project it creates two projects one is the cloud service project and the
other is the web role project. Cloud service project has all the necessary
configuration needed for your cloud service project while the web role project
is your asp.net project.

Step 4:- Set the blob
connection string

Now the next step is to define a blob
connection string in the service configuration file. So expand the ‘BlobStorage’
project, right click on roles and select properties.







Once you select properties, go to settings tab and add the blob connection
string as shown in the below figure. In the below figure we have added blob
connection string name as ‘BlobConnectionString’.





Click on the right hand eclipse and select ‘Use
development storage’. All the changes done using the setting UI will be
reflected in the ‘ServiceConfiguration’ file as shown above.

Step 5:- Create the blob
on webrole onstart

Now it’s time to start coding. Open the web
role project and open ‘WebRole.cs’ file.





Now let’s write a code on the ‘onstart’ event
to create the blob container.

public override bool OnStart()

{





}

Use the ‘CloudStorageAccount’ static class to
set the configuration environment.

public override bool OnStart()

{

// Set the configuration file

DiagnosticMonitor.Start("DiagnosticsConnectionString");

CloudStorageAccount.SetConfigurationSettingPublisher((configName, configSetter) =>

{

configSetter(RoleEnvironment.GetConfigurationSettingValue(configName));

});

....

....

....

....

}

The next step is to get a reference of the
cloudstorageaccount object using the blob connection string which was provided
when you setup your web role project.

// get the blob connection string

CloudStorageAccount objStorage = CloudStorageAccount.FromConfigurationSetting("BlobConnectionString");

Once we have access to the storage account
object, use the blob end point to create the blob client.

// get the client reference

CloudBlobClient objClient = new CloudBlobClient(objStorage.BlobEndpoint, objStorage.Credentials);

Give a nice name to the container and create
the container object using the client object which you have just created using
the blob end point. Call the ‘CreateIfnotExist’ method of the container to
ensure that you create the blob container only if it does not exist to avoid any
errors.

// Get the reference to container

CloudBlobContainer objContainer = objClient.GetContainerReference("mycontainer");



// Create the container if it does not exist

objContainer.CreateIfNotExist();

Step
6:- Code your ASP.NET UI

The final step is to create the ASPX page which
will help us upload image files in the blob container which we just created in
the ‘WebRole.cs’ file. You can see in t he below figure we have create a browse
button which help us upload image files and a search text box which will help us
search blob files.

So create the below defined ASPX UI.





In the above ASPX CS UI first get the reference
to the below specified name spaces.

using Microsoft.WindowsAzure;

using Microsoft.WindowsAzure.StorageClient;

In the file upload button we need to insert the
below code snippet to upload the file. So get access to the container object
‘MyContainer’ and call the ‘GetBlobReference’ function to get access to the
cloud blob object.

// Get the storage account reference

CloudStorageAccount objStorage = CloudStorageAccount.FromConfigurationSetting("BlobConnectionString");

// get the Client reference using storage blobend point

CloudBlobClient objClient = new CloudBlobClient(objStorage.BlobEndpoint, objStorage.Credentials);

// Get Container reference

CloudBlobContainer objContainer = objClient.GetContainerReference("mycontainer");

// Get blob reference

CloudBlob obj =objContainer.GetBlobReference(FileUpload1.FileName.ToString());

Set the meta data of the cloud object and open
a blob stream object to write the file. Do not forget to close the blob steam
object once you are done.

// Set meta values

obj.Metadata["MetaName"] = "meta";

// Open a stream using the cloud object

BlobStream blobstream = obj.OpenWrite();

// Write the stream to the blob database

blobstream.Write(FileUpload1.FileBytes, 0, FileUpload1.FileBytes.Count());

blobstream.Close();

Once we upload the file, we will browse through
the blob list to get the list of blobs present in the container.

// Browse through blob list from the container

IEnumerable<IListBlobItem> objBlobList = objContainer.ListBlobs();

foreach (IListBlobItem objItem in objBlobList)

{

Response.Write(objItem.Uri + "<br>");

}

In the same UI we have provided a search object
to search a blob. To search a blob first get access to the container object and
call the ‘GetBlobReference’ function with the blob name to get reference to the
cloud object.

// Get the blob reference using the blob name provided in the search

CloudBlob obj = objContainer.GetBlobReference(txtSearch.Text);

BlobStream blobstream = obj.OpenRead();

Read the blob stream using the blob steam
object and finally attach this stream with the Image object to display the same
in the HTTP response.

// Create the image object and display the same on the browser response

System.Drawing.Image objimg=null;

objimg = System.Drawing.Image.FromStream(blobstream,true);

Response.Clear();

Response.ContentType = "image/gif";

objimg.Save(Response.OutputStream,System.Drawing.Imaging.ImageFormat.Jpeg);

Step 7:- Run the project and enjoy

Finally enjoy your first blob program. You can
see in the below figure we have uploaded some image files in the blob.





We can also search the blob using the search
blob text box and you should be able to get the below image display from the
blob database.