Viktar Karpach Web Developer Blog about ASP.NET,C#,T-SQL,Javascript,CSS,Silverlight

How to control your iPhone remotely?

Fri, 09 Jul 2010 00:00:00 -0700

Remote control of your iPhone might be very useful for testing iPhone friendly web sites. You can use emulators for this purpose. Blackboud iPhone Browser Simulator is not bad, but still this is not a real iPhone browser.

First of all you iPhone needs to be jailbroken. Then you need to install VNC Server for iPhone. Just search for Veency in Cydia, it is free.

On you desktop you need VNC Viewer. There are bunch of them, but I use UltraVNC since it is free. Then you can connect to your iPhone over Wi-Fi, but you can do it thru USB too.

For USB connection you need to install python interpreter and usbmuxd. From usbmuxd we need only python client part. Run connect.bat, which has following line inside:

c:\python26\python.exe tcprelay.py 5900

And then you can connect to your iPhone using 127.0.0.1 address.

How to fix ViewStateException Invalid ViewState?

Wed, 23 Jun 2010 00:00:00 -0700

Usually you don't see Invalid ViewState exception unless you implement some kind of ASP.NET error logger in Global.asax.

Error usually states something like this:

Exception: System.Web.HttpException: The state information is invalid for this page and might be corrupted. ---> System.Web.UI.ViewStateException: Invalid viewstate.

Those errors are usually generated by some automatic submission form engines. Comments and contact forms are mostly effected by this exception. End user never sees those errors, so invalid viewstate errors don't have any value for your error logger. Let's bypass them:

if (ex is HttpException && ex.InnerException is ViewStateException)

    _app.Response.Redirect(_app.Request.Url.AbsoluteUri)

    return

XRefresh alternative solution

Mon, 31 May 2010 00:00:00 -0700

I am using two monitors for a web development for the past 4 years. Usually I have website that I am working on a left monitor and my Visual Studio on a right monitor. Usually I do change in Visual Studio then press Shift-F6 (in case of code change) or just Ctrl-S (to save). After that I grab a mouse, move cursor to browser on left monitor click and then F5 for refresh. If you do a little CSS tricks it is to much repetitive movements.

About two years ago I discovered XRefresh. I mentioned it in my ASP.NET development tips article. First I was really excited. It is excellent tool for html and CSS markup tweaking. But if you do a lot of code changes and need to recompile your project more often then markup tweaking then it might not be a best tool for you. XRefresh watches files. If file changes then it refreshes browser. Now imagine if you compile big project and compilation takes 15 sec. XRefresh would notice dll change and would try to refresh browser. However compilation is not done yet and some dll-s are locked. So, XRefresh most likely not going to work for Shift-F6 scenario (recompilation of project).

So, I found XRefresh alternative solution. I wrote a Visual Studio macros. You can hook up to OnBuildDone event. Then find Firefox process. Move focus to Firefox window and send F5 keystroke to it. Macros below still needs some polishing, but you can get an idea:

Private Sub BuildEvents_OnBuildDone(ByVal Scope As EnvDTE.vsBuildScope, _ 
 ByVal Action As EnvDTE.vsBuildAction) Handles BuildEvents.OnBuildDone

    Dim projects As Object() = DTE.ActiveSolutionProjects

    If projects.Length > 0 Then

        If CType(projects(0), Project).ExtenderNames.Length Then

            If CType(projects(0), Project).ExtenderNames(0) = "WebApplication" Then

                Dim proc As System.Diagnostics.Process() = _
                          System.Diagnostics.Process.GetProcessesByName("firefox")

                For i As Integer = 0 To proc.Length - 1

                    If proc(i).MainWindowHandle <> 0 Then

                        SetForegroundWindow(New HandleRef(Nothing, proc(i).MainWindowHandle))

                        System.Windows.Forms.SendKeys.SendWait("{F5}")

                    End If

                Next

            End If

        End If

    End If

End Sub

I am open for discussions and any suggestions.

EntitySpaces and LINQ to SQL with multiple where statements

Tue, 23 Mar 2010 00:00:00 -0700

At my current workplace we are using EntitySpaces a lot. I feel guilty but sometimes I am too lazy to write stored procedure, so I rely on EntitySpaces dynamic queries. Usually it involves simple where statement, but sometimes there are multiple where statements based on certain application logic condition. Lets look at example based on table of orders as follow:

Id	Name	Price	Created
1	Viktar	10.00	2010-01-02
2	Viktar	12.00	2010-02-02
3	Alex	15.00	2010-02-02
4	Lucy	11.00	2010-03-10

Let's say you need to filter this table by name and date, but filter values come from different sources. Something like this:

TestTableQuery testTableQuery = new TestTableQuery();

testTableQuery.Where(testTableQuery.Name == "Viktar");

// Some crazy logic here

// ...........

testTableQuery.Where(testTableQuery.Created < customDate);

So, what is relation between first and second where statement? Does second one overwrites first one? Apparently relation is T-SQL AND statement, but you can change it to OR clause as follow:

TestTableQuery testTableQuery = new TestTableQuery();

testTableQuery.Where(testTableQuery.Name == "Viktar");

// Some crazy logic here

// ...........

testTableQuery.es.DefaultConjunction = EntitySpaces.Interfaces.esConjunction.Or;

testTableQuery.Where(testTableQuery.Created < customDate);

I think this is a big advantage that you can do something like this and still get clean T-SQL without nested queries. Here is an output from SQL Server Profiler:

exec sp_executesql

N'SELECT [Id] AS ''Id'',[Name] AS ''Name'',[Price] AS ''Price'',[Created] AS ''Created'' 
FROM [TestTable]
 WHERE [Name] = @Name1 OR [Created] < @Created2'

,N'@Name1 varchar(6),@Created2 date',

@Name1='Viktar',

@Created2='2010-03-23'

Let's try to solve the same task using LINQ to SQL:

using (CoPalletDataContext db = new CoPalletDataContext())

    var q = from t in db.TestTables where t.Name == "Viktar" select t;

    q = q.Where(t => t.Created < DateTime.Now);

    q.ToList();

Code above produces following T-SQL:

exec sp_executesql N'SELECT [t0].[Id], [t0].[Name], [t0].[Price], [t0].[Created]
 FROM [dbo].[TestTable] AS [t0]
 WHERE ([t0].[Created] < @p0) AND ([t0].[Name] = @p1)',

N'@p0 date,@p1 varchar(6)',

@p0='2010-03-23',

@p1='Viktar'

It looks similar to EntitySpaces output. But what if we want OR clause instead of default AND clause? As far as I know it is not possible. So you need to do something like this:

using (CoPalletDataContext db = new CoPalletDataContext())

    var q = from t in db.TestTables where t.Name == "Viktar" || t.Created < DateTime.Now select t;

    if (true) // Some crazy logic here

        q = from t in db.TestTables where t.Name == "Viktar" || t.Created > DateTime.Now select t;

    q.ToList();

In other words rewrite whole query according to your condition.

Dynamic queries are good and save you a lot of time, but it might be challenging for DBA person to optimize it. EntitySpaces queries or LINQ to SQL should be used only for simple queries. If you have more complicated logic put it in stored procedure.

Database reckless modifications. ROLLBACK and COMMIT cure.

Wed, 17 Feb 2010 00:00:00 -0800

One day you might be forced to do modifications on live database and accidentially delete/update all records in table instead of specified in where statement. It happened to me in a past it might happen to you too. Usually you think that world is over. Then you remember about backup, but still there is a possibility that some data would be lost forever. Always make sure to email your records to yourself with a trusted email service provider for further back up. The best solution is as usual prevention of disaster.

There is a reason why SSMS Tools pack by default creates for new queries:

BEGIN TRAN

...

ROLLBACK

Use transaction for all your modifications. Inside transaction you can test if your update/delete does exactly what you want it to do.
Here is a little illustration:

CREATE TABLE TestTable

    Id int identity primary key ,

    [Description] varchar(max)

GO

BEGIN TRAN

insert into TestTable

values

('Test1'),

('Test2'),

('Test3')

select * from TestTable -- First query, returns all records

delete TestTable

where Id=2

select * from TestTable -- Second query, returns two records

ROLLBACK -- COMMIT

select * from TestTable -- Third query, no records because of ROLLBACK

Results:

Query 1:

1	Test1
2	Test2
3	Test3

Query 2:

1	Test1
3	Test3

Query 3:

After you are done with testing, just change your ROLLBACK with COMMIT statement.

T-SQL Form Generator Template

Mon, 25 Jan 2010 00:00:00 -0800

Most of the time web developer spends creating some kind of forms. This is why almost any object-relational mapper product (EntitySpaces, Subsonic, LINQ to SQL, NHibernate) has some kind of scaffolding generators. Generated pages are might be good for admin side, but for front-end those pages needed to be created manually. Front-end usually has specific design requirements, so there you need to do this tedious task manually over and over again.

You can always use T4 templates as code generator, but I prefer to use old solid T-SQL.

Microsoft SQL Server Management Studio has a lot of pre-build templates for you just press Ctrl+ALT+T to see them (View->Template Explorer). If you are not using them yet, check them out it might be really helpful. Hint: Ctrl+Shift+M brings parameter menu.

Let's create simple T-SQL template form generator for ASP.NET:

Declare @width varchar(3)

set @width = '<field_width,int,150>'

select

'<tr>

<td class="textfield">' + COLUMN_NAME + '</td>

</tr>'

from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = '<table_name,sysname,Table Name>'

<field_width,int,150> - width of input box template parameter
<table_name,sysname,Table Name> - table name template parameter
Press Ctrl+Shift+M. Set above parameters. Switch to "Result to Text" mode. Run and your form HTML is ready. Just copy paste it in your aspx file.

This is a good start. But forms are rarely consist of just TextBox-es, so lets modify this a little bit:

select

case

when c.CONSTRAINT_TYPE = 'PRIMARY KEY' then

'<tr>