vb.net

Ambiguous in the namespace problem

28. February 2011 AngryCoder .net , c# , asp.net , vb.net Comments (0)

From the last few days, I was ignoring an error that keep coming at the compile time. I spent some two hours on it before but didn’t get it work. The error is quit confusing and of course difficult to manage.

'ApplicationSettingsBase' is ambiguous in the namespace 'System.Configuration'

'MailMessage' is ambiguous in the namespace 'System.Net.Mail'

And there are couple of other similar errors that is pointing to some ambiguous references in my project. The confusing part is that the MailMessage object throws similar error when you are importing the old and new email namespace.

For example,

Imports System.Web.Mail
Imports System.Net.Mail

So if you are only encountering ambiguous problem in MailMessage object. It is more possible that you have define both the namespaces in your code behind which is actually confusing the compiler about your referencing object.

The quick solve for this problem is that remove Imports System.Web.Mail and it should work smooth. But with me, I never used the old asp.net mail namespace in my project.

Then I start looking at my references and luckily I found the problem there. Follow the steps below to investigate the issue

1. Go to your project

2. Then references

3. Right click on “System” and see properties. it should point to the following path

x:\Windows\Microsoft.NET\Framework\v2.0.50727\System.dll

Where x is name of your operating system directory. This was the problem with my project. I had my operating system install on “D” drive and some how it is pointing to “C” drive which is the root cause of this problem.

After that I verify all my references and found 5 –6 assemblies that are pointing to wrong path and get it worked.

Also note, the problem can occur in any type of project either it is website , web application etc.

How to pass parameters to the dynamically added user control

15. April 2009 AngryCoder .net , asp.net , vb.net Comments (0)

In this post, I will explain how you can pass parameter to the dynamically added (from code behind) User Control. Most of you might aware of how we can achieve this in web application project. Following is the code for that

        1: Dim objCon As Control = Page.LoadControl("~/Controls/MyControl.ascx")       2: Ctype(objCon,MyControl).PropertyOne = "Test"       3: Ctype(objCon,MyControl).PropertyTwo = "USAM"       4: MyPanel.Controls.add(objCon)  

Now what if you have a web site project which does not have the pre-compiled assemblies and you are no more able to access the class of your user control. That is what the sum of last two ays.

Here is how you can do that by using System.reflection.

       1: Dim objCon As Control = Page.LoadControl("~/Controls/MyControl.ascx")       2: 'Creating Dynamic Assmebly which holds control       3: Dim objAssembly As Assembly = Compilation.BuildManager.GetCompiledAssembly("~/Controls/MyControl.ascx")       4: 'You should definately know the name of your user control class       5: Dim objType As Type = objAssembly.GetType("Controls_MyControl")       6:         7: 'Properties       8: Dim objPropOne As PropertyInfo = objType.GetProperty("PropertyOne")       9: Dim objPropTwo As PropertyInfo = objType.GetProperty("PropertyTwo")      10:        11: 'Setting Value of Properties      12: bjPropOne.SetValue(objCon, 1, Nothing)      13: objPropTwo.SetValue(objCon, 13, Nothing)      14:        15: 'Finally placing control on the page      16: pnlCommentsCon.Controls.Add(objCon)  

So in this way you can pass parameters to the dynamically added user control.

Get Repeater Control Output in String

13. April 2009 AngryCoder asp.net , vb.net Comments (0)

In this post I will share with you a small code snippet which will help you to get the repeater control output in string variable.

        1: Dim sb As New StringBuilder()       2: Dim objHtml As New HtmlTextWriter(New System.IO.StringWriter(sb))       3:         4: If dt.Rows.Count > 0 Then       5:     Repeater1.DataSource = dt       6:     Repeater1.DataBind()       7: End If       8:         9: Repeater1.RenderControl(objHtml)      10: Return sb.ToString()   

Well, I have used a little trick here. The RenderControl method of repeater control can put all the HTML in HtmlTextWriter Object and from HtmlTextWriter Object we have simply dump the output the to the string builder. That’s it ….

Get Column name From Stored Procedure

9. March 2009 AngryCoder .net , SQL Server , vb.net , TSQL Comments (0)

The requirement of the day is to extract the name of the columns returned by procedures. Stored Procedures are dynamic that is why we need to create a function that takes Stored Procedure name as parameter and return the column names in string. So here is the quick snippet for that

        1: Public Shared Function getMetaData(ByVal spName As String) As String()       2:        Dim sqlCon As New SqlConnection(ConfigurationManager.ConnectionStrings("lmString").ConnectionString)       3:        sqlCon.Open()       4:         5:        Dim sqlCmd As New SqlCommand("sp_helptext " + spName, sqlCon)       6:        Dim sqlDataAdapter As New SqlDataAdapter(sqlCmd)       7:        Dim dt As New DataTable       8:        Dim strTempQuery As String = String.Empty       9:        Dim strColumns As String()      10:        Dim strCol As String = String.Empty      11:        12:        sqlDataAdapter.Fill(dt)      13:        If dt.Rows.Count > 0 Then      14:            For Each dr As DataRow In dt.Rows      15:                strTempQuery += dr.Item(0)      16:            Next      17:        End If      18:        19:        If Not strTempQuery = "" Then      20:        21:            'Dim objRegex As New Regex("select([^<]*)from")      22:        23:        24:            Dim objMatches As MatchCollection = Regex.Matches(strTempQuery, "select([^<]*)from", RegexOptions.IgnoreCase)      25:        26:            For Each mymatch As Match In objMatches      27:                strCol += mymatch.Groups(1).Value      28:            Next      29:        30:            If Not strCol = "" Then      31:                strColumns = strCol.Split(",")      32:                For a As Integer = 0 To strColumns.Length - 1      33:                    strColumns(a) = strColumns(a).Trim()      34:                Next      35:            End If      36:        End If      37:        Return strColumns      38:    End Function  

Restriction : Though, we have achieved the target, but since we have used sp_helptext to extract the Stored Procedure data that is why it is not possible to process encrypted stored procedure.

Will make it more better in the future to accommodate all type of Stored Procedures.

Send Welcome email to user using Membership API

2. February 2009 AngryCoder .net , vb.net , Membership API Comments (0)

While using Membership API, It is a very normal task to send user a registration or verification email. We can achieve that using two ways one is using the default email setting of Create User Control and other is by implementing CreateUserWizard.CreatedUser event

Method 1:

Drag and Drop the create user control, right click then properties and find MailDefination and set appropriate values for each property.

BodyFileName is basically the location of the file which contains the body of the email. It can be text file or html file.

HTML file which I am using is a very simple html file which can be found in the project source specified at the end of this post.

Create User Control uses the SMTP settings in web.config to send the email that is why before checking it you need to make sure that you have specify the correct settings in configuration file. For example

        1: <system.net>       2:     <mailSettings>       3:         <smtp deliveryMethod="Network">       4:             <network defaultCredentials="true" host="localhost" port="25"/>       5:             <!--userName="" password="" if required specify after port-->       6:         </smtp>       7:     </mailSettings>       8: </system.net>  

That's it your control is now ready to send emails.

Method 2:

In this method, we will manually shoot an email when the user get registered successfully. For that we need to implement our logic in CreatedUser event of this control.

Following is the screen shot of different events provided by CreateUserControl

As you can see I have generated a method against CreatedUser and here is the code for that

       1: Protected Sub CreateUserWizard1_CreatedUser(ByVal sender As Object, ByVal e As EventArgs) Handles CreateUserWizard1.CreatedUser       2:     Dim ToAddress As String = CreateUserWizard1.Email       3:     Dim mm As New MailMessage("Support@mysite.com", ToAddress)       4:     Using objSr As New StreamReader(Server.MapPath("MailTemplate\\welcome_ver.htm"), FileMode.Open)       5:         With mm       6:             .Subject = "Welcome to my site"       7:             .Body = objSr.ReadToEnd()       8:             .Body = .Body.Replace("{verification_code}", New Random().Next()) 'Any Random number you can put your logic here...       9:             .IsBodyHtml = True      10:         End With      11:         Dim smtp As New SmtpClient      12:        13:         smtp.Send(mm)      14:     End Using      15: End Sub  

In this method I am also using the SMTP Settings specified in web.config however, you can change that according to your own need.

In line no 10, I have put a token which will replace the string which I have in my source html file with a random number. For those who are facing difficulty in understanding the token stuff, please see the following html

       1: <html>       2:         3: <body>       4: Hi,        5:         6: Thank you for the registration and welcome to my site       7: Your verification code : {verification_code}       8: </body>       9: </html>  

That is very simple and very easy. I personally recommend the Method 2 as it can give you some extra control over the process.

Here is the VS 2008 code

Long Waited Task in Asp.net

22. January 2009 AngryCoder .net , asp.net , vb.net , AJAX Comments (0)

Yesterday, one my my friend ask me a query about sending some 500+ emails using an asp.net page. Sending bulk email using asp.net is obviously an issue. I mean, You cannot keep the page on the post back state for the five minutes. Your page will get expired and even if you increase the Request Timeout period it is still not a good approach.So for that, There are couple of approaches like1. You can have a table in which you store all the emails and create a Windows Service or Schedule Task to read tables of send emails accordingly.2. Open a thread on the server side using delegate and return the page to the browser and show the progress using Asynchronous operation. As We were operating on shared hosting first approach doesn't seem fruitful for us. So, we decided to go with the second approach and for that we use delegates. Let me show you step by step.

1: Public Delegate Sub LongTimeTask_Delegate()2: Private fileName as String

Here I have declared a delegate and a global variable called filename which I will use for getting the status of the process.Now on the click event of my button which start the process. I have write the following code

1: Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click2: Dim rnd As Double = New Random().Next()3: fileName = Session.SessionID & "_" & rnd & ".txt"4: Dim d As LongTimeTask_Delegate5: d = New LongTimeTask_Delegate(AddressOf LongTimeTask)6:  7: Dim R As IAsyncResult8: 9: R = d.BeginInvoke(New AsyncCallback(AddressOf TaskCompleted),nothing)10: Dim strScript As String = "<script language='javascript'> setInterval('GetResult(""" + fileName + """)',2000); </script>"11:  12: Button1.Enabled= False13: Response.Write(strScript) 'TODO : Can take write on literal14: End Sub

On line no 3, I am setting filename variable to the session id and a random numberOn line no 4, Declare and Initialize Delegate and passed a function that will be executed by DelegateOn line no 7 and on, We invoke the delegate and store the result in IAsyncResult and also specify the function that will execute once the delegate is complete.On line no 10, we are writing a script on the page which is there to show us the status of process timely.Now, lets come LongTimeTask function, in which we have the whole stuff.

1: Public Sub LongTimeTask()2: Dim totCount As Integer = 5003: For a As Integer = 1 to totCount4: Try5: If Not File.Exists(fileName)6: File.Create(fileName)7: End If8: using sw As StreamWriter = New StreamWriter(Server.MapPath(fileName))9: sw.WriteLine("Processing " + a.ToString() + " of " + totCount.ToString() + " emails")10: End Using11: Catch 12:  13: End Try14: System.Threading.Thread.Sleep(2000)15: Next16: End Sub

Notice that, system will be in the loop for 500 times and each time before start processing it will update the status which will display to the browser. The Try/Catch block is updating the status where as notice the line no 14 in which I pause the thread. You can add your email sending or other long process stuff here but for me it is enough to sleep the thread for twenty seconds.Let me show you what happen when the task gets finished.

1: Public Sub TaskCompleted(ByVal R As IAsyncResult)2: Try3: using sw As StreamWriter = New StreamWriter(Server.MapPath(fileName))4: sw.WriteLine("Process has been completed successfully <a href='default.aspx'>Click here </a> to go back") 'You might shoot an email or some thing else here5: End Using6: If File.Exists(fileName)7: File.Delete(fileName)8: End If9: Catch 10:  11: End Try12: End Sub

This time, we have updated the status with some other text and a hyper link. You can also have any kind of alert here. This is just the part of the code behind stuff. ASPX file contain the actual Asynchronous logic here is the HTML

1: <form id="form1" runat="server">2: <div>3:  4: <asp:Button ID="Button1" runat="server" Text="Start IAsync" />5: <div id="resultDiv"></div>6: </div>7: </form>

The resultDiv is responsible of showing the status. Now to get the status following Javscript will do the complete magic

1: <script language="javascript">2: var request = false;3: try {4: request = new XMLHttpRequest();5: } catch (trymicrosoft) {6: try {7: request = new ActiveXObject("Msxml2.XMLHTTP");8: } catch (othermicrosoft) {9: try {10: request = new ActiveXObject("Microsoft.XMLHTTP");11: } catch (failed) {12: request = false;13: } 14: }15: }16: 17: function GetResult(filename) {18: var rnd = Math.random() * 1000000;19: var url = filename + '?rnd=' + rnd;20: request.open("GET", url, true);21: request.onreadystatechange = GetResultComplete;22: request.send(null);23: }24: function GetResultComplete() {25: if (request.readyState == 4) {26: 27: if (request.status == 200) {28: var divComm = document.getElementById('resultDiv');29: if (divComm) {30: divComm.innerHTML = request.responseText;31: }32: }33: }34: }35: </script>

There it is ... we are all done. Following is the snapshot of the working long waited task in asp.net

You can find the complete code for Visual Studio 2008 ... cheers

Prevent .js caching in asp.net

6. January 2009 AngryCoder .net , asp.net , vb.net Comments (0)

This is like a very common issue, specially for those who are working on public site which is live and they have to release the builds every week or month and if the new build contain JS files then your change will not reflect on the client browser until someone there presses ctrl + F5.So, after googling this issue. I came to know it is possible to prevent the browser from accessing the cache copy by writing the script tag as below

   1: <script type="text/javascript" src="../Includes/main.js?random=556"></script>

It is good, when I have a single or some number of pages to change. Unfortunately, That is not the case I have hundreds of pages and that will be hassle to make those changes again and again for every build. So, I try to make this thing happen using Response Filter.

Create Response Filter:

So, to write the Response Filter we need to create a class and which is extended from Stream (System.IO.Stream) and I named it BuildTokenFilter.

   1: Imports Microsoft.VisualBasic   2: Imports System.IO   3: Imports System.Text.RegularExpressions   4: Imports System.Configuration   5:    6:    7: Public Class BuildTokenFilter   8:     Inherits Stream   9:     Private _responseStream As Stream  10:     Public Sub New(ByVal responseStream As Stream)  11:         _responseStream = responseStream  12:     End Sub  13:     Public Overrides ReadOnly Property CanRead() As Boolean  14:         Get  15:             Return _responseStream.CanRead  16:         End Get  17:     End Property  18:     Public Overrides ReadOnly Property CanSeek() As Boolean  19:         Get  20:             Return _responseStream.CanSeek  21:         End Get  22:     End Property  23:   24:     Public Overrides ReadOnly Property CanWrite() As Boolean  25:         Get  26:             Return _responseStream.CanWrite  27:         End Get  28:     End Property  29:   30:     Public Overrides Sub Flush()  31:         _responseStream.Flush()  32:     End Sub  33:   34:     Public Overrides ReadOnly Property Length() As Long  35:         Get  36:             Return _responseStream.Length  37:         End Get  38:     End Property  39:   40:     Public Overrides Property Position() As Long  41:         Get  42:             Return _responseStream.Position  43:         End Get  44:         Set(ByVal value As Long)  45:             _responseStream.Position = value  46:         End Set  47:     End Property  48:   49:     Public Overrides Function Read(ByVal buffer() As Byte, ByVal offset As Integer, ByVal count As Integer) As Integer  50:         Return _responseStream.Read(buffer, offset, count)  51:     End Function  52:     Public Overrides Function Seek(ByVal offset As Long, ByVal origin As System.IO.SeekOrigin) As Long  53:         _responseStream.Seek(offset, origin)  54:     End Function  55:   56:     Public Overrides Sub SetLength(ByVal value As Long)  57:         _responseStream.SetLength(value)  58:     End Sub  59:     Public Overrides Sub Write(ByVal buffer() As Byte, ByVal offset As Integer, ByVal count As Integer)  60:         Dim strRegex As String = "src=(?<Link>.*js)"  61:         Dim BuildTokenString As String = "?token=" & IIf(ConfigurationManager.AppSettings("BuildToken") = Nothing, "1.0", ConfigurationManager.AppSettings("BuildToken"))  62:         Dim objRegex As New Regex(strRegex)  63:         Dim html As String = System.Text.Encoding.UTF8.GetString(buffer)  64:         Dim extCharCount As Integer = 0  65:   66:         Dim objCol As MatchCollection = objRegex.Matches(html)  67:         For Each m As Match In objCol  68:             extCharCount += BuildTokenString.Length  69:             Dim newJSValue As String = m.Value & BuildTokenString  70:             html = html.Replace(m.Value, newJSValue)  71:         Next  72:         buffer = System.Text.Encoding.UTF8.GetBytes(html)  73:         _responseStream.Write(buffer, offset, count + extCharCount)  74:     End Sub  75: End Class

"Write" is the function which is doing the whole stuff. It is really simple to understand. Let me go linewise.

60. Create a string variable and assign and regular expression which will search all the js files tags in html61. Create a string which will append to the JS file. Checking the App key in web.config So that the token can be extended in future.62. Create a Regex Object63. Get the html from Buffer64. Create an integer variable which will keep track of the characters that are added to the html variable. 66. Save the matches in a collection67. Get each mach object from Match Collection68. Add the character count which will added to the html variable69. Create a variable and assign value of match and concatenated with build token70. Replace the old value with the new with build token in html variable72. Encode the html variable back to the buffer73. Write the buffer to the stream by adding count with build token character count.

Now lets create a HttpModule which will responsible of attaching this response filter with every request.

Create HttpModule:

Now to write HttpModule, I will create a class which will Implements IHttpModule (interface) and I name it "BuildToken"/

   1: Imports Microsoft.VisualBasic   2: Imports System.Web   3: Public Class BuildToken   4:     Implements IHttpModule   5:     Public Sub Dispose() Implements System.Web.IHttpModule.Dispose   6:    7:     End Sub   8:     Public Sub Init(ByVal context As System.Web.HttpApplication) Implements System.Web.IHttpModule.Init   9:         AddHandler context.BeginRequest, AddressOf Application_BeginRequest  10:     End Sub  11:     Private Sub Application_BeginRequest(ByVal source As Object, ByVal e As EventArgs)  12:         Dim context As HttpApplication = CType(source, HttpApplication)  13:         If context.Request.RawUrl.Contains(".aspx") = True Then  14:             context.Response.Filter = New BuildTokenFilter(context.Response.Filter)  15:         End If  16:     End Sub  17: End Class

In this case the magical function is Application_BeginRequest which can easily be understand but the question might arises why I have put the If condition on line number 13. Well, I don't want my module to attach response filter against all the files. Keep in mind, HttpModule is always called no matter what content type are you requesting. when somebody write http://www.sitename.net/images/border2.jpg it will still process through HttpModule and that is what I don't want.

Configuration Setting:

We are almost done, just a web.config entry is left which we keep for the modification of token string.

   1: <appSettings>   2:     <add key="BuildToken" value="7.0"/>   3: </appSettings>

Test the filter:

Now to check the the response filter create a page that is called default.aspx and paste the following markup

   1: <html xmlns="http://www.w3.org/1999/xhtml" >   2: <head runat="server">   3:     <title>Untitled Page</title>   4:     <script type="text/javascript" src="../Script/samain.js"></script>   1:    2:     <script type="text/javascript" src="../ControlsScripts/preloadshare.js">   1: </script>   2:     <script type="text/javascript" src="../Script/mainview.js"></script>   5: </head>   6: <body>   7:     <form id="form1" runat="server">   8:     <div>   9:     <p>  10:     Right click and view source you will find JS files with query string</p>  11:     </div>  12:     </form>  13: </body>  14: </html>

Now Run the application and view source the page you will notice some thing like give below.

Each time, when you made some changes in JS file just change Build Token entry in the web.config file and your visitors will get the updated copy of JS. You can also download the project files.

Downloading Zip File Using Asp.net

29. December 2008 AngryCoder .net , asp.net , vb.net Comments (0)

Here is the quick code of downloading the zip file from asp.net (vb.net)

   1: Dim _strBeingViewedName As String = "MyZip"   2: Response.ContentType = "application/x-zip-compressed"   3: Response.AppendHeader("Content-Disposition", "attachment; filename=" + _strBeingViewedName + ".zip")   4: Response.TransmitFile("..\\zipPath\\" & _strBeingViewedName + ".zip") 'Full Path of the zip file   5: Response.End()