Mapping varchar(max) - using micorosoft application data blocks (No mapping exists from DbType .. to a known SqlDbType ....)

I have been happily using application blocks for various tasks in my project and the data blocks was one of them. I had code like this which worked fine ..

Dim lDatabase As Database = DatabaseFactory.CreateDatabase()
Dim lCommand As DbCommand = lDatabase.GetStoredProcCommand("dbo.pr_service_WriteLog")
lCommand.CommandType = CommandType.StoredProcedure
'-- add the parameters
lDatabase.AddInParameter(lCommand, "@CreatedOn", SqlDbType.DateTime, DateTime.Now)
'-- add the error type
lDatabase.AddInParameter(lCommand, "@LogType", SqlDbType.VarChar, EntryType.ToString)
lDatabase.AddInParameter(lCommand, "@LogType", SqlDbType.VarChar, lLogBase.Type.ToString)
'-- add the message
lDatabase.AddInParameter(lCommand, "@LogMessage", SqlDbType.VarChar, lLogBase.Message)

lDatabase.ExecuteNonQuery(lCommand)

This worked fine for quite sometime till I had a new requirement to write a SP which had to insert into a table a fields with the data type defined as varchar(max). To apss this new type from the UI to SP I tried
lDatabase.AddInParameter(lCommand, "@NewParam", SqlDbType.text, MyValue)

It gave the error "No mapping exists from DbType UInt16 to a known SqlDbType." ..
So I tried various other types like Nvarchar etc etc .. but all failed .. Then I started reading about the data types supported by the data block and I came to realise that instead of using SQLDbType, i could use DBtype directly. So I tried DBtype.string and it worked !!!

Hope this helps someone who might get stuck in a similar area ....

"Exception has been thrown by target of invocation" Error

You might face this error and wonder what happened. I had a similar situation today. The code was working fine and all of a sudden I got this error. I am not that kind of person who beleives very strongly that all errors are due to some bad coding, maybe by the developer or maybe thrown bt the tools used for development. Till now, whenever I have been involved in coding or debuging someone's problem , I have managed to at least find out where the issues have been and most of time solve it too. Anyway, so I started tracing my steps backwards and commenting recenlty changed codes. But still was not able to find exactly where the error is occuring.

Finally, during one my debug attempts, I happened to look at the exception object's inner exception and noticed the error was because of a new addition I had on the app.config file. I made the correction and the error was gone. BTW, the change I did was add a "configSections" tag at the end of the app.config file. If you add a "configSections" tag, it has be the first line after the "configuration" tag.

So to conclude, if you get this error ""Exception has been thrown by target of invocation"", look at the inner exceptions. Keep looking recursively into the inner exception's "inner exception" till you see "nothing" and hopefully you see the actual error message and correct the problem.

happy coding !!

Public member 'OverRideMethod' on type 'ObjectHandle' not found. [Reflection - Access methods from class dynamically]

I had a hard time with this. Spend around 2-3 hours trying various options till i got a clue from one of the links on the internet.

I had a class library (dll) referenced in a windows project and all the classes in this dll is inherited from a base class. The baseclass is mustinherit and has mustoverride function. My plan was that this windows application would have a list of (dynamically maintained using a XML file in the windows application) classes and its methods that can be executed from this dll. Each of the class within this dll overrides the mustoverride function from the baseclass and does some actions. The reason for this design was to make a "plug and play" kind of application. So if i wanted to add a new functionality, i just need to add a new class to the dll, edit the XML file and the front-end will show this new functionality and it will execute it. There were many other functions that were specific to the project that need not be discussed here .. Anyway, this sounded very simple to me and i started with writing the code..

The first thing that came into my mind was whether i would have to use reflection. But the dll was referenced in the main windows project. So there was no need to load a assembly dynamically and i did not want to go with that approach. Then found from the help about Activator.CreateInstance which has a overloaded function which accepts 2 strings .. the assembly name and the class name .. this was what i wanted. So i wrote this

Dim lObject As Object
lObject = Activator.CreateInstance("Namespace.MyAssembly", "Derived Class Name")
lObject.OverRideMethod

But this kept giving an error on the line where it is executing overriden method.
Public member 'OverRideMethod' on type 'ObjectHandle' not found.

I was sure that the object was getting created because when i changed the assembly or the class name, it gave the error on that line. So what was the issue? I could not get any help in MSDN. So i started searching the net and luckily got a link which said that Activator.CreateInstance does not give a object in return, but returns a object handle. I checked MSDN and it said that it gave back a object. I aklso noticed now that the error I got mentioned that "... on type ObjectHandle not found" So I decided to give it a try.. So I changed the code to

Dim lHandle As System.Runtime.Remoting.ObjectHandle
lHandle = Activator.CreateInstance("Namespace.MyAssembly", "Derived Class Name")
lRulesObject = lHandle.Unwrap()
lRulesObject.OverRideMethod

Lo and behold, it worked !! ..

I also type cast my object to the baseclass so that I can now call the method from the baseclass directly.. So my final code was

Dim lHandle As System.Runtime.Remoting.ObjectHandle
Dim lRulesBase As MyBaseClass
Dim lRulesObject As Object

lHandle = Activator.CreateInstance("Namespace.MyAssembly", "Derived Class Name")
lRulesObject = lHandle.Unwrap()
'-- cast it to the base class
lRulesBase = DirectCast(lRulesObject, MyBaseClass)
'-- call the service method
lRulesBase.OverRideMethod()

I spend some time finding this out and i thought I will post this for others who might have similar issues.

Happy coding !!

Icon size in notifyicon

Recently I had a requirement to create a windows service in .net. This service also had to have a "form" like a "dashboard" functionality that showed the status of the service and various options that the user could do to make changes to the service functions. For this, I decided to show a icon in the taskbar when the service starts and onclick of this icon, I would show the form.

This can be done using notifyicon control in .net and its pretty straightforward. But the issue I was facing was with the icon been shown in the taskbar. It was never clear and after trying various options like different size etc, i searched the net and found this article which was useful - http://www.hhhh.org/cloister/csharp/icons/

------ from the above link ------
"A reader asked for a quick-reference table at the top of this document, showing the default icon versions used by Windows Forms applications in different circumstances, so here it is. Detailed explanations are provided below if you're interested

Circumstance: Icon Version:
Control Box 16x16x256
Taskbar 16x16x256
Notify Icon 32x32x256, shrunk down (see below)
Desktop Shortcut 32x32x256 (Normal sized icons)
48x48x256 (Large sized icons)
Add/Remove Programs 16x16x256
Folder Browse dialog 16x16x256

Notify IconIf you add a NotifyIcon control to your application's Form object, then your application will display an icon in the tray area of the taskbar. The rendered size of the notify icon is the same as for the Control Box and Taskbar icons: 16x16 pixels, potentially stretched to accomodate the height of the system tray, which is dependent on the height of the Taskbar. Oddly, however, Windows does not use the 16x16x256 bitmap for this circumstance; it uses the 32x32x256 bitmap by default, and squashes it down to the required size. I can think of no particularly good reason for this difference--using the 32x32 version for the notify icon, but 16x16 for taskbar and control box--but there it is.

16x16 Notify Icon 18x18 Notify Icon


Notice that the text on my 32x32x256 icon is barely readable when shrunk down to 16x16 size. The same will be true for any one-pixel-wide details you include in your 32x32x256 bitmap, unless you are very careful about where you put them. The reason for this is clear: a 16x16 bitmap has only one-quarter as many pixels as a 32x32 bitmap. Consequently, three-quarters of the information in the 32x32 bitmap is thrown away when shrinking it down to 16x16. What to do about it is less clear.

To get a more optimal appearance for your NotifyIcon, you need to know which pixels out of the 32x32 bitmap are the ones that will be displayed at 16x16 size. Fortunately, the mapping is straightforward. Windows throws out all the even-numbered rows and columns, and keeps what's left. Shown here at double-size is a 32x32x256 bitmap, where the black pixels are the ones that will be seen when the bitmap is shrunk down to 16x16 on a NotifyIcon, and the actual NotifyIcon image that this bitmap turns into in the system tray:
Before: ...and after:
As you can see in these two images, the black pixels in the 32x32 image are the ones that are actually displayed at 16x16 size. The yellow has disappeared because the even-numbered rows and columns are thrown away. Pixels in the even-numbered rows and columns are important for the appearance of desktop shortcut icons, but are irrelevant for NotifyIcon objects.

Custom validator controls : Change style of label when error occurs

ASP.net

We had this unique requirement from a client that when a validation failure occurs like "required field is not filled", the corresponding label must be highlighted with a different color. As all of you might already be aware, we attach the validator controls to the control that needs to be validated and not the label. For eg, if you have a "Customer name" field with a textbox (txtCustomer) which is mandatory, you add a requiredFieldValidator with its ControlToValidate property = txtCustomer.

So how do you now highlight the label "Customer name" .. lets say with a different background color. Ofcourse, doing that on the server is easy, but that negates the reason of using validator controls which does everything on the client (browser). So I decided to build a custom control by inheriting from the standard requriedFieldValidator control. I added a new property called LabelToHighlight which will accept a control name whose styles needs to be changed when an error occurs. I reaserched on how to allow user (consumer the control) to be able to select a label (like you selecting controls when setting the ControlToValidate property) and not just type in a control name and I came across typeconvertor settings available for properties .. anyway, given below is some of the code .. you can write to me for more explanation if needed ..

'Created by Rejo on Aug 23rd 2007
' Standard field validators has just the controltovalidate property which can be set to specify which
' controls needs to be validated. But the delivery.com project requires the errors to highlight the label
' of the control which is been validated.
' This custom validator does just that.
' A new property added gives option to the developer to select a control which gets highlighted with a different style.
' The styles are set as embeded resource and should be changed as per the requirement of the project
' The styles too could have been exposed as public properties, but that would be each control will have to manually
' set by the developer.
' The javascript which changes the style is also embeded into the project
' ONLY THE DLL NEEDS TO BE REFERENCED IN THE MAIN PROJECT which will consume these controls

Imports Microsoft.VisualBasic
Imports System.Web.UI
Imports System.ComponentModel
Imports System.Web.UI.WebControls

Namespace Controls

_
Public Class CustomRequiredValidator
Inherits System.Web.UI.WebControls.RequiredFieldValidator
Dim lstrLabelToHighlight As String

_
Public Property LabelToHighlight() As String
'property to hold the name of the label control which would be highlighted when the error occurs
Get
Return lstrLabelToHighlight
End Get
Set(ByVal value As String)
lstrLabelToHighlight = value
End Set
End Property

Protected Overrides Sub AddAttributesToRender(ByVal writer As System.Web.UI.HtmlTextWriter)
'set the display property to none
Me.Display = ValidatorDisplay.None
MyBase.AddAttributesToRender(writer)
'add the custom properties
writer.AddAttribute("LabelToHighlight", Me.LabelToHighlight)
End Sub

Private Sub CustomRequiredValidator_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender
Dim ctlParent As System.Web.UI.Control = Me.Parent
Dim lLableHighlight As Label = TryCast(ctlParent.FindControl(LabelToHighlight), Label)

While lLableHighlight Is Nothing
ctlParent = ctlParent.Parent
If ctlParent IsNot Nothing Then
lLableHighlight = TryCast(ctlParent.FindControl(LabelToHighlight), Label)
Else
Throw New Exception("Control to highlight is not found.")
End If
End While

LabelToHighlight = lLableHighlight.ClientID

'check if the script is already present and if not, then add it
If Not Me.Page.ClientScript.IsClientScriptIncludeRegistered("ControlsCommon.js") Then
Dim lstrScriptLocation As String = Page.ClientScript.GetWebResourceUrl(Me.GetType(), "Delivery.ControlsCommon.js")
Page.ClientScript.RegisterClientScriptInclude("ControlsCommon.js", lstrScriptLocation)

' add the style .. assumming that the style too would be added only once along with the js file

Dim lstrLocation As String = Page.ClientScript.GetWebResourceUrl(Me.GetType(), "Delivery.ControlStyle.css")
Dim lobjIncludeLiteral As LiteralControl = New LiteralControl(String.Format(lstrTemplate, lstrLocation))
CType(Page.Header, HtmlControls.HtmlHead).Controls.Add(lobjIncludeLiteral)

'register submit script which will call the script which will highlight the control if there is a error
Me.Page.ClientScript.RegisterOnSubmitStatement(Me.GetType(), "HighlightLabelSubmit", "UpdateErrorLabel();")
End If
End Sub
End Class
End Namespace

Code from the COMMON.js file

Function UpdateErrorLabel()
{
var lobjValidator;
//first reset all the existing validators to default style
for (i = 0; i < Page_Validators.length; i++)
{
lobjValidator = document.getElementById(document.getElementById(Page_Validators[i].id).getAttribute('LabelToHighlight'));
if (lobjValidator != null)
{
lobjValidator.className = 'lblnormal';
}
}


//change the style for all error labels
for (i = 0; i < Page_Validators.length; i++)
{
if (!Page_Validators[i].isvalid)
{
//lobjValidator = document.getElementById(Page_Validators[i].LabelToHighlight);
lobjValidator = document.getElementById(document.getElementById(Page_Validators[i].id).getAttribute('LabelToHighlight'));
if (lobjValidator != null)
{
//lobjValidator.setAttribute('class', 'lblerror');
//lobjValidator.setAttribute('className', 'lblerror');
lobjValidator.className = 'lblerror';
}
}
}
}

This does have some flaws which I have learnt to overcome like sometimes when you add the this control, the highlight does not work. As you can see from the code, I have to add on to the standard validation code that asp.net generates which checks for the isvalid property and then change the style when it is false. Some my functions get added to the front and so this js always finds the isvalid = true and does not validate. For these cases, I just remove the Custimvalidator and add it again and it works .. :-) ..

Note, you will need the style 'lblError' etc to be available in your stylesheet referred by the page ..

This line is not getting accepted by this blogpost when added in my code above..

it must be in the prerender event .. i will try and make some changes to the code so that this post gets accepted
Dim lstrTemplate As String = "<link rel='stylesheet' text='text/css' href='{0}' CLOSING TAGS"

Include files (.js, .css) in master pages or base page

We always use master page and basepage implementation for our asp.net projects.

Even after master pages were introduced in VS2005, i continued using basepage.vb file which inherits from system.web.ui.page. I inherit this in all my pages. Its just that I found more flexibility and control by using basepages and master page. basepage contains all the codes that need to fired for each page like authentication, validations etc,. and the masterpage just contains the UI framework ..

anyway, maybe I can explain my reasons for this implementation in some other post .. let me continue with the reason for this post .. Now there was this requirement to inlude some common .js files in all my webpages. I thought I could do this in master page. But it did not work ..

so finally I got it to work using this statement in the load of my basepage.vb class.

MyBase.ClientScript.RegisterClientScriptInclude("CommonJS", "~/Common/Scripts/Common.js")

where Common.js resides in the Root\Scripts directory of the project ..

WebControl - Embed javascript in control

I had to build a custom control which had to use javascript on the borwser and change some setting. For this, I used the clientscripts.register... methods to emit the javascript to the browser. I was not happy about this because it meant that every page will now need to emit the same code and it is not cached. So I thought of using a .js file with the same javascript code and register that within the control. But now the issue was the path of the .js file. I wanted a generic solution where the project consuming this control need not worry about where the js files needs to be picked from. That is when I came to know about embedding .js files into web controls.

Use these statement to do it and you will no longer need to distribute the .js file with your control

If Not Me.Page.ClientScript.IsClientScriptIncludeRegistered("ControlsCommon.js") Then
Dim lstrScriptLocation As String = Page.ClientScript.GetWebResourceUrl(Me.GetType(), "ControlsCommon.js")
Page.ClientScript.RegisterClientScriptInclude("ControlsCommon.js", lstrScriptLocation)
End if

where ControlsCommon.js is the file that I need to include and it resides in the same directory where the controls is present (in the development environment). No need for this .js file when the control is consumed in another project

IVR calls using .Net

Lots of research was done by one my collegue on this and we narrowed down to VBVoice from Pronexus using Dialogic boards (http://www.pronexus.com/english/view.asp?x=1).

There were other options like some product from microsft too (I think it was communication server), but it was still in beta and we do not trust microsoft beta versions :-) ..

An update : I realised that Pronexus has its own limitations. It has something called a VBVFrame and all controls are supposed to added within this frame. Unfortunately you cannot have 2 vbvframes running on the same machine at the same time. As told by their support, it interacts with the dialogic boards to make the call and it cannot handle more than one frame active at any one time. So my whole ides of multi-threading went down the drain. Anyway, vbvoice has its own way supoprt for multithreading. It is not actually threading as you would like it, but its kind-of for our requirement.

In short, even though they have .net support, it looks like all the controls were build really fast as wrappers on top of COM objects that they had created earlier. So i do not think that it is really leveragin the use of the .net framework. I would recommend that you continue searching for somthing better and you might want to come back to this if others options do not have all the functionalities that you need. VBVoice does seem to have a lot of options, but their help file is really bad ..

How to Fax using .Net - HTML to TIFF

I had to build a fax soltution for one of my application. So again as usual, I started my research by searching on the net. Another collegue of my mine suggested using microsoft fax server. We were also using a third party software for "Interactive voice response" requirement from pronexus and this software also had faxing capabilities. So I narrowed down on these 2 application. Now my issues started.

I had fax information that I was reading from my database. The information had to be formatted. So I thought of faxing HTML documents. That is when I realised that Fax expects images or text files as the source document. The image has to be in TIFF format and it has to have specific encoding. I started with microsoft fax server, and the encoding requirements for this server is not very strict and it kind of accepts all types of TIFF images. But our requirement was to be able send multiple faxes at the same time (through multiple phone lines) and be able to process them in parallel. So this meant using multiple modems or getting a hardware which behaves as a modem for fax server. I was not too sure about this implementation and so I moved to VBFax (from pronexus)

We had already purchased dialogic boards for the IVR solution and I wanted to use this same boards to fax. The development board had 4 ports and in production we will be having a sigle bpard with 48 ports so that we can processes 48 requests in parallel. Now that I had narrowed down my hardware, the issue in hand was how to convert HTMl to TIFF format

There are lots of solutions available for this. But all of them is implemeted as printers i.e. you install it as a printer and you fire a print command (using code or any application File->print menu) and select this printer and it converts the currently opened file into TIFF. I was not too happy with this solutions because HTML files by default are opened by IE (or any browser) and when you print a opened document, it shows the print dialogbox. Now this has to be implemented as server and there cannot a user sitting and hitting the "ok" button. So how to avoid this print dialog. By the way, this was another reason why I moved away from Microsoft Fax server because its fax client also gets installed a printer. So again more reasearch and I found some other solutions like the ones from black ice software (http://www.blackice.com/), Informatik Image Driver 3.50 (http://www.informatik.com/), Zan image printer (http://www.zan1011.com/) and lots of others .. Some even like the one from back ice had .Net support which I needed. But it costs around $2000 .. what???? yes, too expensive

Luckily I found another software which converts HTML strings to TIFF.This was eactly what I wanted. So now I could just read the database and create a TIFF file directly. No need to create the HTML file and send it to the "Image" printers which would have been an expensive (with respect to time) affair .. This software was from Guangmingsoft called "HTMLSnapshot". I did have to talk a lot with their support to get the created TIFF iamge to work with my dialogic boards. Their support (David) was very helpful too. I finally have managed to get it working and hopefully everything works smoothly .. Its still under development .. I will update as we proceed ..

Please wait ... message in ASP.net

I have heard lots of questions on how to implement this and these links seems to provide the answers ..

Loading Progress and Status Displays in ASP.NET http://www.informit.com/articles/article.asp?p=174363&rl=1

Building a Better Busy Box - Ver 1.2(Processing… Please Wait)http://blogs.crsw.com/mark/articles/642.aspx

Javascript "Please Wait" Message Boxes -
http://aspalliance.com/38
gives the complete code using jaascript .. u could implement the same script for a page load too by not encapsulating the code within the function but directly within script tags .. remember the page is buffered by default is asp.net i.e. the page is not diplayed till the whole thing is not processed and so the browaser waits for it to complete and then receives the complet page .. so u could try and use response.flush in the page load to load the initial scripts ..

PleaseWaitButton ASP.NET Server Control
http://www.codeproject.com/aspnet/PleaseWaitButton.asp