Vishwamohan.NET

Secure Query String using Symmetric Cryptography

Vishwa — Wed, 28 May 2008 23:43:00 -0400

It is important to secure information on the web specially when transferring data from one page to another. Some information you may not want to make it readable by end user. Microsoft .NET provides Cryptography namespace which can be easily utilized for this purpose. The following example contains a simple class containing Encryption and Decryption method. It supports 2 types – DESC and Rijndael. Symmetric type and encryption key can be configured easily through .config file. Read More

Error: Could not establish trust relationship for the SSL/TLS secure channel with authority

Vishwa — Fri, 18 Apr 2008 23:37:00 -0400

I got this error when calling a WCF Service over HTTPS. A Similar error can also occurs when you try calling a web service programmatically over SSL (HTTPS) and certificate is either not valid or Certificate is attached to a domain and you are not using the domain name but the machine name or IP address. So, what to do in that case if you don’t care about certificate and would like to accept all certificates. I found that it can be done using one of two ways. Read More

Make a .NET Component accessible in Classic ASP or VB6

Vishwa — Sat, 05 Apr 2008 17:54:00 -0400

I came across a situation again to use exactly same .NET component as COM component in classic ASP page. I had totally forgotten these steps but finally managed to make it work. Later, I thought to put these steps together on my blog, so that if anyone else also don’t know or forget these steps, this will help. Read More

Implementing WCF Service Part 5

Vishwa — Tue, 25 Mar 2008 00:07:00 -0400

In WCF, there are five major contracts – Service Contract, Operation Contract, Data Contract, Fault Contract and Message Contract. In my previous examples I used first three. In this example, I will implement the Fault Contract. I am not very fond of using Message Contract as some guidelines suggest using the least or based on requirement, however you cannot get away from the first four contracts. In the event of Fault (exception), WCF throws a fault containing detail error message which you may not like to be passed back to the caller. In other words, this example focuses on how to hide full error details and provide a custom error code, message and details. You can use multiple Fault Contracts on one Operation Contract in similar way. This example provides a simple and generic way to handle Faults. Read More

Implementing WCF Service Part 4

Vishwa — Fri, 08 Feb 2008 00:21:00 -0400

This post will focus on implementing POX (Plain Old XML) and REST (Representational State Transfer) in WCF. In other words this is an implementation of the old HTTP XML Post. I spent not several hours but several days to figure out the solution. As all of you know making HTTP GET is easy in WCF but HTTP Post (without using SOAP) is a different story. I researched all around the web but nowhere found a simple example for this option, yes not even on Microsoft site. Many people just post their opinion in few lines and then you keep guessing, and if you are new to this then just keep doing trial and error method for hours and days provided you keep your patience on. Once you will find the solution, it will look so easy. Read More

Implementing WCF Service Part 3

Vishwa — Sat, 02 Feb 2008 08:38:00 -0400

In this post, I will implement the basicHttpBinding, through which you can even use a HTML page and JavaScript to consume the WCF Service via SOAP based XML. I spent several hours to exactly figure out the SOAP format. In ASMX web service, if you will click on a method, it shows you the sample SOAP format for request and response. Unfortunately, that is not available in WCF Service page right now, so you have to figure out or use a tool to see what is being passed or expected. The Serialization used in ASMX Web Service is based on XML Serialization; however WCF uses a different mechanism for the same. You can use the old SOAP format (which I used in ASMX Web Service) to post the transaction but you will always get SOAP 1.2 format response. In order to keep consistency, I kept the request format similar to response. Read More

Implementing WCF Service Part 2

Vishwa — Sun, 20 Jan 2008 00:49:00 -0400

I will consume the Customer WCF Service which I developed in Part 1 on WS* Http Binding, you can implement the best security, transactions and many more things using this way. However, I will consume in a very simplistic way in this post. I assume that you have already deployed the WCF Service under IIS and have a working URL ready to be referenced and you are planning to use the customer WCF service in ASPX web Page. Read More

Implementing WCF Service Part 1

Vishwa — Sat, 19 Jan 2008 23:28:00 -0400

As you know, the New Windows Communication Services (WCF) will replace the existing ASP.NET ASMX Web Services. So, it will be wise to plan it from today as how to transit in this new service model era. I first tried experimenting with WCF Service almost a year ago with the release of .NET 3.0 but VS 2005 and VISTA did work happily on my machine but now I like VS 2008. I revisited WCF again with the release of .NET 3.5, all the sample available on the web are either old or do not give enough information if you are looking for information as how to use this service in different way over different protocol, which can closely mimic a small real word example . So, I had to spend hours trying to find solutions and put the pieces together. So, I finally thought to create an example to help others who are facing the same situation. I have tried to closely mimic the ASMX Web Service uses, which I posted in my earlier post because most of us will be planning to convert from existing old one. With all the experiments I would give one key Mantra for WCF, dig the Config file specially to understand how to configure BEB (Binding, Endpoint and Behavior). This example deals with CRUD operation on Customer data which I used in earlier post. For the simplicity I am using XML file for the data source and will consume this service with WS* Standard, SOAP based XML POST, Plain Old XML (POX) and HTTP GET and POST. I believe these are the common uses along with TCP, named pipe and MSMQ. Read More

Implementing ASMX Web Service Part 2

Vishwa — Fri, 18 Jan 2008 02:29:00 -0400

In this post, the web service created in Part 1 will be consumed into a web page through Server Side Web Service Integration, Client Side SOAP XML HTTP Post, HTTP Form Get and Post. Read More

Implementing ASMX Web Service Part 1

Vishwa — Thu, 17 Jan 2008 02:36:00 -0400

You must be wondering, that in WCF era ASMX Web Service! I wrote the first one 5 years ago and now trying to move them to WCF Service, but lot of companies have not even adopted the web service and some have only started adopting it recently, and now they realized that a new era has come. I will discuss my experiments & experiences with WCF in later post. However, I would like to post a simple Customer ASMX Web Service and then consume it by a ASP.NET Web Page via Server Side and then Client Side using direct SOAP based XML through HTTP Post. Later, I will create a similar WCF Service with exactly same methods and will access the data exactly same way. Remember this is not a simple HelloWorld Example, this Web Service deals with primitive data type as well as complex one. How far you would like to dive deep, it will be up to you. Read More

Catch Your Application Errors

Vishwa — Thu, 10 Jan 2008 21:26:00 -0400

You must be thinking that my web site is working great and generating no errors. But have you ever tried catching errors on Application_Error event in Global.asax, it catches all unhandled errors. Try applying the following code, and you will be amazed to see that your site is generating some errors which you were not even aware of. The following method will dump all the erros into a XML file which will be create on montly basis. Initially I was sending these errors to my email, but it is not easy to analyze all the data at once. XML file can be imported in Excel easily and you can fix the code which is generating more errors.

Drop the following lines of code in your global.asax file - Make sure you choose one format, otherwise you will logging errors twice.

Sub Application_Error(ByVal sender As Object, ByVal e As EventArgs)
Dim exc As Exception = Web.HttpContext.Current.Server.GetLastError()
If TypeOf exc Is Web.HttpUnhandledException Or exc.InnerException IsNot Nothing Then exc = exc.InnerException

        If exc IsNot Nothing Then
            'Attribute Format - Small File Size - less readability
            Call LogErrorAsXMLFileAttribute(exc, Request.ServerVariables("SERVER_NAME"), Request.ServerVariables("REMOTE_ADDR"), Request.ServerVariables("HTTP_REFERER"))

            'Element Format - Large File Size - more readability
            'Call LogErrorAsXMLFileElement(exc, Request.ServerVariables("SERVER_NAME"), Request.ServerVariables("REMOTE_ADDR"), Request.ServerVariables("HTTP_REFERER"))
        End If

End Sub

The Subroutines LogErrorAsXMLFileAttribute and LogErrorAsXMLFileElement are available on my previous post Create XML Data file with Element vs. Attribute Format.

Create XML Data file with Element vs. Attribute Format

Vishwa — Wed, 09 Jan 2008 21:10:00 -0400

You can choose to create a XML file in which detail records are represented as Elements or Attributes only. It is wiser to use the best use of both, more use of attribute reduces the size of xml file and increases the speed over wire. Representation of data in Elements only XML file becomes heavier in file size thus slower the transmission. The only benefit is when you open this file in browser it is relatively easily to read. Following are an example for creating a file with same information in two different ways.

XML Element Format

This format takes more file size, but increases the readability of file in browser. This example can be used for gathering all the exceptions generated during application uses.

Private Sub LogErrorAsXMLFileElement(ByVal excep As Exception, ByVal serverName As String, _
Optional ByVal remoteHostAddress As String = "", Optional ByVal referer As String = "")

        Dim xmlDataDoc As New XmlDataDocument
        Dim xmlDeclare As XmlDeclaration = Nothing
        Dim rootNode As XmlNode = Nothing
        Dim childElement As XmlElement = Nothing
        Dim parentElement As XmlElement = Nothing

        Try
            Dim rootTag As String = "Errors." & serverName.ToLower
            Dim filePathName As String = WebConfigurationManager.AppSettings("ErrorLogFolder") & "\" & _
                                        serverName & ".ErrorLog." & Format(Now(), "yyyyMM").ToString & "E.xml"

            If File.Exists(filePathName) Then
                xmlDataDoc.Load(filePathName)
                rootNode = xmlDataDoc.GetElementById(rootTag)
            Else
                xmlDeclare = xmlDataDoc.CreateXmlDeclaration("1.0", Nothing, Nothing)
                rootNode = xmlDataDoc.CreateElement(rootTag)
                xmlDataDoc.AppendChild(rootNode)
                xmlDataDoc.InsertBefore(xmlDeclare, rootNode)
            End If

childElement = xmlDataDoc.CreateElement("Error", "")
rootNode.AppendChild(childElement)

            parentElement = childElement
            childElement = xmlDataDoc.CreateElement("ID", "")
            childElement.InnerText = XmlConvert.ToString(Guid.NewGuid)
            parentElement.AppendChild(childElement)

            childElement = xmlDataDoc.CreateElement("DateCreated", "")
            childElement.InnerText = XmlConvert.ToString(Now, XmlDateTimeSerializationMode.Local)
            parentElement.AppendChild(childElement)

            childElement = xmlDataDoc.CreateElement("RemoteHostAddress", "")
            childElement.InnerText = remoteHostAddress
            parentElement.AppendChild(childElement)

            childElement = xmlDataDoc.CreateElement("Referer", "")
            childElement.InnerText = referer
            parentElement.AppendChild(childElement)

            childElement = xmlDataDoc.CreateElement("Message", "")
            childElement.InnerText = excep.Message
            parentElement.AppendChild(childElement)

            childElement = xmlDataDoc.CreateElement("Exception", "")
            childElement.InnerText = excep.ToString
            parentElement.AppendChild(childElement)

xmlDataDoc.Save(filePathName)

        Catch exc As Exception
            Throw New Exception(exc.Message)
        Finally
            xmlDataDoc = Nothing
        End Try

End Sub

XML Attribute Format

This format takes less file size, but decreases the readability of the file in browser. This example can be used for gathering all the exceptions generated during application uses.

Private Sub LogErrorAsXMLFileAttribute(ByVal excep As Exception, ByVal serverName As String, _
Optional ByVal remoteHostAddress As String = "", Optional ByVal referer As String = "")

        Dim xmlDataDoc As New XmlDataDocument
        Dim xmlDeclare As XmlDeclaration = Nothing
        Dim rootNode As XmlNode = Nothing
        Dim childElement As XmlElement = Nothing

            If File.Exists(filePathName) Then
                xmlDataDoc.Load(filePathName)
                rootNode = xmlDataDoc.SelectSingleNode(rootTag)
            Else
                xmlDeclare = xmlDataDoc.CreateXmlDeclaration("1.0", Nothing, Nothing)
                rootNode = xmlDataDoc.CreateElement(rootTag)
                xmlDataDoc.AppendChild(rootNode)
                xmlDataDoc.InsertBefore(xmlDeclare, rootNode)
            End If

            childElement = xmlDataDoc.CreateElement("Error")
            With childElement
                .SetAttribute("ID", XmlConvert.ToString(Guid.NewGuid))
                .SetAttribute("DateCreated", XmlConvert.ToString(Now, XmlDateTimeSerializationMode.Local))
                .SetAttribute("RemoteHostAddress", remoteHostAddress)
                .SetAttribute("Referer", referer)
                .SetAttribute("Message", excep.Message)
                .SetAttribute("Exception", excep.ToString())
            End With

rootNode.AppendChild(childElement)
xmlDataDoc.Save(filePathName)

        Catch exc As Exception
            Throw New Exception(exc.Message)
        Finally
            xmlDataDoc = Nothing
        End Try
    End Sub

Certificate Error: Navigation Blocked

Vishwa — Wed, 02 Jan 2008 12:27:00 -0400

There are some situations especially in development or QA environment when you would to like ignore the SSL certificate. Generally this warning occurs when SSL certificate is either assigned to a different domain name, IP Address or self signed. You will most likely see the one of following error or warning messages when information is posted manually through Internet Explorer or FireFox browser.

1. There is a problem with this website's security certificate.
2. The security certificate presented by this website was not issued by a trusted certificate authority.
3. Website Certified by an Unknown Authority.
4. Unable to verify the identity of release as a trusted site.

If you are trying to post a transaction to such URL programmatically, this warning message will come internally and program will finally throw an exception.

In order to eliminate this issue, the following settings in Web.config will ignore the certificate.

<system.net>
         <settings>
               <servicePointManager checkCertificateName="false" checkCertificateRevocationList="false"/>
           </settings>
</system.net>

BlogEngine Stored Procedures

Vishwa — Fri, 28 Dec 2007 21:27:00 -0400

I have updated my BlogEngine from inline SQL statements to Stored Procedures. In order to do that I modified the MS SQL Server Provider class and wrote all stored procedures. If you like to upgrade your code, download the attached files and follow the steps:

Login to your SQL Server database and run the Stored Procedure SQL Script. This file contains all the stored procedures. It should create 33 stored procedures.
Open BlogEngine.Core Project in Visual Studio 2005/8, replace MSSQLBlogProvider.cs under Providers. You may copy the existing file and rename it as MSSQLBlogProvider.cs.old for backup and then replace the existing class.
Compile the BlogEngine.Core project and drop it into bin directory of BlogEngine Web folder.

That’s all. You are done. I am using the same code on this web site for last 5 days and till now, I have not come across any issue. So, if you find any please let me know. Thanks

MSSQLSetup1.3.0.0_AllStoredProcedures.sql (36.10 kb)

MSSQLBlogProvider.cs (33.17 kb)

Welcome to my New Blog

Vishwa — Sun, 23 Dec 2007 19:04:00 -0400

Hello Everyone,

This Blog is running on BlogEngine.NET 1.3, which was released yesterday. This site is using SQL Server 2005 for data storage. It is really a great work by BlogEngine Team. Thank You so much. Certain things I wanted to do and some of them I have already done it, if you are using the same engine and a developer, you might be thinking of these things too.

1. Converting to Visual Studio 2008 with .NET 3.5

Successfully converted both projects - BlogEngine.Core and BlogEngine.Web under .NET 3.5. Initially I was unable to compile the web site into a single assembly because every theme has same name for master page. If you would like to compile your BlogEngine Web Site project, just keep the theme which you want for your website for compilation.

2. Converting In-Line SQL Statements to Stored Procedures

Successfully converted all the In-Line SQL Statements of MSSQLBlogProvider.cs class to corresponding Stored Procedures. I believe as the number of posts will grow on blog, stored procedures will provide the best performance.

If you want the source code of MSSQLBlogProvider.cs class and its stored procedures, you are welcome to contact me; I would love to help the BlogEngine Community.

Thanks