Category Archives: HOWTO

All topics that have the potential to give a full walk through or how to on a specific subject.

How to consume an OAuth based REST service

Recently I decided to dive deep into REST services because of how prominent they are becoming in the industry.  Nearly most of my coding time is spent figuring out how to take one piece of software or code and connect it with another piece of software or code to produce the expected result.  RESTful web services are a great way to take a generic design such as Json or XML and come up with a standard library to talk to any system.  If you aren’t familiar with REST services, they are a simple form of HTTP communication that takes basic HTTP commands: GET, PUSH, PUT and DELETE and translates them into CRUD operations.

What does this all mean?  It means that you can call a website through a standard website client and treat it just as if you were hitting a data source.  Pretty neat huh?  A large chunk of the REST services out on the market now deal in Json with support for XML.  Json is a nice language that allows for dynamic object design without having any formal definition.  If you want to add a field, you add it.  It is very extensible and light weight allowing for quick and scalable data operations.

So how does OAuth play into all of this?  OAuth is a system that allows you to connect your application to another application in a secure fashion.  To start out, you give your application an ID.  This is sent to a service in the form of a request for access, and the user who is using your application grants what access they want to give.  Once granted your application gets back an authorization key which it uses to make future calls.  The beauty of this system is it puts the security and functionality of the application in the hands of the user and the end service.  All you need to worry about is what your authorization key is and how what services you should be calling at a given time.

My goto library for this type of call currently is called RestSharp.  This library is a REST service library built out for everything we are doing here.   Here is an example of how to create a client and make a call:

Dim auth = New RestClient(SiteURL)
Dim rqst As New RestRequest("wc-api/v2/orders", Method.GET)
Dim rtn As RestResponse

rqst.RequestFormat = DataFormat.Json
auth.Authenticator = New HttpBasicAuthenticator(ConsumerKey, ConsumerSecret)
rtn = auth.Execute(rqst)

With this call, you are reaching out to a popular WordPress plugin called WooCommerce to get a list of orders and returning back the HTTP response.  This response will be in a Json string that you can parse using the popular Newtonsoft library.  The request has all of the standard CRUD operations as well as numerous authentication libraries on top of OAuth.  For more details information about REST services or OAuth, check out the standards page here on W3C.

.NET Applications on Linux

Well, what a touchy subject this might be to some people.  I have always seen the battle go back and forth between Windows, Macintosh and Linux.  Windows being a middle-tier price range which excellent performance, Macintosh being the high end simply from marketing and Linux being the low end cost point which the most potential.  The problem I have always seen is that Microsoft holds the middle share which is always the most used share.   I have been a Microsoft developer for my entire career and I love it to death, but the power behind a Linux machine is starting to become hard to ignore.  Recently I ran into a project that was faced with spending 100 hours developing a communication platform for a piece of software or somehow getting .NET hooked into a Linux server.

Of course we went both routes as with any project whichever option is the best is the choice, but something has to work.  I came across this plugin for Apache and Linux called Mono.  Mono is a plugin/server application that lets you run ASP.NET applications on your Linux server native.  You do not have to get pushed to another server or lose your performance, you simply install the package and configure it in Apache and you are up and running.  To start, here is the mono website for you to check out and hopefully spread out through all of your Linux servers: http://www.mono-project.com/Main_Page

Hopefully you all install it and configure it so when I come through I can install my applications on your server and be just fine and dandy, if you don’t I will no doubt make you do it :)  There is a set of install instructions for each server type including Mac servers as well as CentOS, Ubuntu, Debian, etc.  Mostly it seems to just be a package installation through w-get or whatever your package flavor is.  After configuration you can use this site to configure virtual directories: http://go-mono.com/config-mod-mono/Default.aspx

The nice thing about this configuration generator is that you can create a separate config file for each virtual directory and include them in your base httpd config file under each virtual host settings section.  It is almost exactly like creating virtual applications in IIS and the performance is for the most part the same.  From what I have seen this far, .NET 4.0 is supported as well as AJAX, and I am hoping to see some more stuff go into the project to make it a viable option for hosting .NET applications.  Cheers!

Prevent SQL Injection Attack With .NET

There has been a large stir recently with how to prevent SQL injection attacks with .NET.  Huge rumors are flying about viruses because of the nuclear incident that happened in Iran.  Just to be clear, regardless of how secure any site is there is a likelihood that you can be hacked.  The best we can do is prevent as much as possible so that it takes someone who is really good to do it.  At that point you are dealing with a security expert and likely they will just want you to pay them for the information.  Back on to the subject, to solve our security problem we must first ask ourselves, what is a SQL injection?  SQL injections are a trick that hackers use to execute malicious SQL scripts on your server.

Our main goal is not to take away functionality, but to prevent SQL injection attacks

Let’s say you have a login form, and you ask for a username and password.  You have a text box bound to both fields and when they hit a Login button your form code selects from the user table where user name is equal to the User text box.  The SQL might look something like this:

SELECT UserId, UserName,Password FROM Users
WHERE UserName = '" + txtUserName.Text + "'

prevent sql injection attacks
This is where a hacker can come in and where we need to prevent SQL injection attacks.  The user name a hacker would fill out would be something like this:

'; DROP DATABASE myWebApp --

When your code executes it will send a drop database command to your server destroying all of your data.  This is likely not the intent of the hacker as they would much rather send a command to validate their password or fetch data but the goal here is to prevent SQL injection.  Here are the three big steps to prevent SQL injection attacks:

Three methods to prevent SQL injection attacks with .NET

Validate your data

The first step in a SQL injection attack is to know what the developer is expecting to happen with a field and exploit it.  In reverse, the first step to prevent SQL injection attacks is to know what a hacker intends to do with a field and prevent it.  This will involve checking that your text received is the right length, scrubbing for invalid characters and make a decent attempt at stripping out dangerous SQL commands or throwing back errors if you find anything.

Use SQL Stored Procedures

Stored procedures are the next great .NET tool, because a parameter passed through a stored procedure command is sent as literal text as opposed to executed with a command.  While converting your commands to a stored procedure does not prevent SQL injection attacks it does give you an additional security layer in case the injection makes it through and is targeting specific commands.

Use Parameters with Dynamic SQL

Another way to prevent SQL injection attacks is to embed your input from forms as parameters as opposed to injecting them directly into the statement.  This can be done simply by using an @ sign as a parameter in your statement and appending a parameter to your command object.  This looks something like this:

SqlDataAdapter saoSqlAdapter = new SqlDataAdapter(
         "SELECT UserName, UserId, Password FROM Users WHERE UserName = @userName",
         connection);
  myCommand.SelectCommand.Parameters.Add("@userName", SqlDbType.VarChar, 50);
  myCommand.SelectCommand.Parameters["@userName"].Value = txtUserName.Text;
  myDataAdapter.Fill(userDataset);

Other methods to prevent SQL injection attacks

After working these three methods you should be able to prevent SQL injection attacks from mostly all attackers, if you need more information on how to prevent SQL injection attacks check out how to prevent sql injection attacks on MSN.

XML to XML – Translating XML with C#

Working with XML documents is the new way of EDI in today’s business work.  XML to XML provides a way to not only translate data that you want to work with, but also provides a way to store extreme amounts of information in a structured manner.  In this article I will discuss how to use XML in two forms, XML to XML or moving one XML document to another XML document and translating it along the way and XML to Object.  XML to Objects will be used in the XML to XML process but it will also help with keeping your XML uniform as well.

The most important piece in XML to XML is uniform documents

Starting out with a fresh document is very important in being successful in translation.  Here is an example of a simple yet effective XML document:

xml to xml job definition

The first part of XML to XML is to load the document into a XmlDocument file.  We do this through instantiating a XmlDocument and calling the Load method targeting our file.  The XmlDocument will be used to populate our new document and then write out to finish our XML to XML process.

            XmlDocument xmlJobDoc = new System.Xml.XmlDocument();
            XmlDocument xmlLoadDocument = new System.Xml.XmlDocument();
            XmlNode xmlJobNode;
            XmlAttribute xmlAttribute;
            XmlNode xmlRootNode = xmlLoadDocument.CreateElement("Root");
            xmlJobDoc.Load("JobDefinition.xml");
            for (int i = 0; i < 2; i++)
            {
                xmlJobNode = xmlLoadDocument.CreateElement("TruckRun");
                xmlAttribute = xmlLoadDocument.CreateAttribute("JobNumber");
                xmlAttribute.Value = i.ToString();
                xmlJobNode.Attributes.Append(xmlAttribute);

                xmlJobNode.AppendChild(xmlLoadDocument.ImportNode(xmlJobDoc.DocumentElement,true));
                xmlRootNode.AppendChild(xmlJobNode);
            }
            xmlLoadDocument.AppendChild(xmlRootNode);
            xmlLoadDocument.Save("JobFile.xml");

Xml to Xml utilizing Xml ImportNode Command

This will utilize the Xml to Xml specific command called ImportNode. ImportNode is powerful as it allows you to copy one specific section of an Xml document to another Xml document or use the Xml to Xml functionality as if you were copy and pasting. To finish up the Xml to Xml translation, we utilize the Save method on the Xml document and push the information to the specified file.  If you would like to learn more about translating Xml documents from Xml to Xml or other Xml processing capabilities of Microsoft dotNet Framework, check out this MSDN article.

HOW TO: Write Your First Outlook 2010 Addin

Writing an Outlook 2010 Addin is a very easy task given the tools that Microsoft provides.  While it does require some knowledge about what you are doing and where you are going, overall the Outlook 2010 addin functionality is a robust system that gives you the flexibility you need to get the information required.

I am a big supporter of Outlook as an email client as well as a scheduling tool.  A huge advantage that Microsoft Office has over most of the competition is the ability to easily write addins and communicate with all other tools that are Office related.  An Outlook 2010 addin is no exception to this and it provides a great way to embed ideas and activities into your own interface without much work.  Developing an Outlook 2010 addin has been designed to be so easy that you can start right away simply by installing Visual Studio 2010 and Office 2010.

Creating an Outlook 2010 Addin

To get started an Outlook 2010 addin, Open up the New Solution window and navigate to the Office -> 2010 Section of your preferred language.

outlook 2010 addin - new  solution window

As a test, let’s create a custom tab in our Outlook and use it to pop a Hello World window.  To do this, open the Add New Item window and navigate to Office -> Ribbon (Visual Designer)

outlook 2010 addin - new  item window

How to implement an Outlook 2010 Addin that shows a new ribbon

To choose which Ribbon you are modifying, select the Ribbon Type on the right hand side.  For this example I chose the Explorer Ribbon so it shows up directly on the Office 2010 main ribbon.

On the left side of the Ribbon Designer you will get some nice pre-built Microsoft Office controls to use, simply drag a button onto the Ribbon.

outlook 2010 addin - new  ribbon button

At this point simply double click your button to bring up an event and type in the Message Box command to print Hello World.  If your Outlook is running you will need to close it to deploy.  Once closed, run your add-in through debug mode and it will pop up Outlook with your added loaded into it.

outlook 2010 addin - hello world

Writing an Outlook 2010 addin can be very simple or very complex based on what you want to do with it.  Just like with any coding you should start easy and have fun to start.  If you are interested in more information about writing an Outlook 2010 addin check out this MSDN article for more detail.