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7 Simple Steps to Run Your First Azure Blob Program

, 26 Feb 2014
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7 simple steps to run your first Azure Blob Program

Table of Contents

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.

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Step 1: Ensure You Have Things In Place

In case you are a complete fresher to Azure, please ensure you have all the pre-requisites in place. You can read this article to get the basic prerequisites.

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 this article 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 ellipse 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 code in 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 the below figure that we have created a browse button which will 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 a 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 that 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.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Shivprasad koirala
Architect http://www.questpond.com
India India

I am a Microsoft MVP for ASP/ASP.NET and currently a CEO of a small
E-learning company in India. We are very much active in making training videos ,
writing books and corporate trainings. Do visit my site for 
.NET, C# , design pattern , WCF , Silverlight
, LINQ , ASP.NET , ADO.NET , Sharepoint , UML , SQL Server  training 
and Interview questions and answers


Comments and Discussions

 
QuestionWeb Role and Worker role Pinmemberbmulinti22-May-11 19:49 
QuestionHow do you created these images PinmemberJitendra Zaa18-May-10 21:01 
AnswerRe: How do you created these images PinmvpShivprasad koirala18-May-10 21:43 
GeneralRe: How do you created these images PinmemberJitendra Zaa18-May-10 21:45 
QuestionSteps for deployment/usage in the actual Azure Blob? Pinmemberrghubert1-Apr-10 9:28 
GeneralIf you are getting the exception " One of the request inputs is out of range.": Pinmemberp100017-Feb-10 7:18 
GeneralConfiguring the blob container for public access. Pinmembergreghsr2-Feb-10 11:20 

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