Sunday, February 7, 2010

Lambda Expressions: A replacement to anonymous functions

I recently started looking at LINQ on .Net 3.5 and came across the concept of Lambda expressions and realized they are the perfect replacement to anonymous methods we used in .Net 2.0

Lets assume we have a room where there is some kind of celebration going on and we want to give some special gifts to all the senior citizens who have attended this celebration. So we add a list of people to the room (Joe, Kathie, Sam, etc..) and later we display a list of all senior citizens with their age so we can call out their names and give them the special gift.

  • Create a class that will store the name and age of a person.
  • Create a class which makes use of the above class as collection.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
public class Person
    public string Name { get; set; }
    public int Age { get; set; }

    public Person()

public class PeopleInRoom
    public List People = new List();
    public PeopleInRoom()

    public IEnumerable SeniorCitizens20()
        return People.FindAll(delegate(Person p) { return p.Age >= 60; }); //Uses anonymous method

    //Lambda Expressions
    Func senior = p => p.Age >= 60;
    public IEnumerable SeniorCitizens35()
        return People.Where(senior);        

While implementing we have to create the list of people in a room and then filter it to have the names with their age who qualify as senior citizens (aged 60 or more).

protected void Page_Load(object sender, EventArgs e)
//Add people to the list
PeopleInRoom people = new PeopleInRoom();
people.People.Add(new Person("Joe", 50));        
people.People.Add(new Person("Kathie", 63));
people.People.Add(new Person("Sam", 59));
people.People.Add(new Person("John", 62));
people.People.Add(new Person("Aniada", 60));
people.People.Add(new Person("Alice", 49));

Response.Write("Using Anonymous Methods(2.0):
//Filter the list using anonymous method as predicate
foreach (Person p in people.SeniorCitizens20())
Response.Write(p.Name + " - " + p.Age.ToString() + "
"); //List the names along with age

Using Lambda Expressions:
//Filter the list using Lambda expression as predicate
foreach (Person p in people.SeniorCitizens20())
Response.Write(p.Name + " - " + p.Age.ToString() + "
"); //List the names along with age

lets see the important sections in the above snippets of code
public IEnumerable SeniorCitizens20()
        return People.FindAll(delegate(Person p) { return p.Age >= 60; }); //Uses anonymous method
This is the section where we are using 2.0 anonymous method which you can pass as a delegate to filter the items in a collection. The same becomes much more easier with 3.5 and Lambda by declaring the predicate as a Lambda expression
Func senior = p => p.Age >= 60;
    public IEnumerable SeniorCitizens35()
        return People.Where(senior);        
The first line in the above snippet tells we have a object of type Person and the expression is going to return a Boolean and the name of the expression is senior. Further, the variable p is going to represent the object Person and the last part is the condition you are going to check which in our case is if the property Age has a value 60 or more. Just like we used predicates in .Net 2.0 we can use the Lambda expression as our predicate.

I found this new way of filtering collections quite interesting and thought of sharing my experience. I am looking forward to exploring .Net 3.5 more and try to blog my experiences which i feel are worth mentioning.

I hope this helps some if not all who are just starting to look at .Net 3.5 and its capabilities.

Happy Coding!!

Wednesday, August 26, 2009

MS Excel friendlier to MS Access than to SQL 2005

Ever come across this error while trying to import data into SQL Server 2005 from Excel?
"Text was truncated or one or more characters had no match in the target code page.". (SQL Server Import and Export Wizard)
I came across this and googled with no luck. I realized I had faced this same situation some time earlier and my rescue was MS Access. It seems MS Excel is more friendlier to MS Access while MS SQL is less forgiving. If you run across this issue the simplest solution is to import the data in MS Access and then Import the data to MS SQL from MS Access. I agree this is an extra step but its better than spending time fixing the Excel import in MS SQL when you really don't want to be spending time fixing something which you may not want to use quite often.

Having said the above, there may be better ways of resolving this. If you know of any pls do leave a comment with the solution or link.

Happy Programming...

Friday, May 22, 2009

Backup all Databases on SQL Server

You work from 9 am to 6 pm and around 4 someone comes up to you and says "We got a problem. We need the backup of all 50 databases on our server and I want you to do that before you leave for the day." What is your reaction to that? And guess what, you are not even a Database Administrator.

All you know is this:
  1. Open SQL Server Management Studio.
  2. Connect to a Database Engine.
  3. Right click on the database you want to back up.
  4. Select Tasks.
  5. Select Back Up.
  6. Add a backup destination.
  7. Specify the name of the backup.
  8. Hit "OK".

Wow that was easy :)
But then you realise, you have to repeat this process for FIFTY databases so 50 times 8 Steps = 400 steps.. WOW.. now this is going to take quite a while. Say goodbye to your evening plans cause your boss just made you HIS plan :D

Then you think.. maybe someone can help me automate this. Thats when Paul Hayman comes to rescue. He has made this cool script which will backup all the databases on a SQL instance. This script saved me hours of work. No more clicking around.. just run the scrips. Following is the script, hope it helps:

DECLARE @DBName varchar(255)


        DATABASE_NAME   = db_name(s_mf.database_id)
        sys.master_files s_mf
       -- ONLINE
        s_mf.state = 0 

       -- Only look at databases to which we have access
    and has_dbaccess(db_name(s_mf.database_id)) = 1 

        -- Not master, tempdb or model
    and db_name(s_mf.database_id) not in ('Master','tempdb','model')
    group by s_mf.database_id
    order by 1



    declare @DBFileName varchar(256)    
    set @DBFileName = datename(dw, getdate()) + ' - ' + 

    exec ('BACKUP DATABASE [' + @DBName + '] TO  DISK = N''c:db backup' + 
        @DBFileName + ''' WITH NOFORMAT, INIT,  NAME = N''' + 
        @DBName + '-Full Database Backup'', SKIP, NOREWIND, NOUNLOAD,  STATS = 100')


So there you are, just a single script to take care of all that and now you can go ahead with your evening plans ;)

Thursday, February 26, 2009

Going crazy with "unable to start debugging on web server" in Visual Studio 2005?

So ever tried to setup visual studio 2005 on a new machine and all you want to do is just debug a application in IIS? I recently attemped doing this and got the friendly error message: unable to start debugging on web server. the web server is not configured correctly vs2005 Does not help does it? The message too generic and the thing(s) that caused it unknown So after googling for over 3 hrs and trying number of proposed solution, I came across a forum where Chandan Gowda had the right solution for it. Here is the post
  1. iisreset -stop
  2. Goto C:\Windows\Microsoft.NET\Framework\v2.0.50727
  3. aspnet_regiis -ua
  4. aspnet regiis -i
  5. aspnet_regiis -ga machinename\aspnet
  6. goto C:\Windows\Microsoft.NET\Framework\v1.1.4322
  7. aspnet_regiis -i
  8. iisreset -start

  • Uninstall all versions of .Net frameworks using aspnet_regiis -ua
  • Re register the version of .Net framework using aspnet_regiis -i
  • Add machine's aspnet user to the web operator group using aspnet_regiis -ga machinename\aspnet
  • And you are done.
The Problem: I installed IIS after installing Visual Studio. I did run aspnet_regiis -i to re register .net but did not add the aspnet user to the web operator group.

Always Remember: Make sure IIS is installed before you install any version of Visual Studio Hope this information will save someones time and help reduce the frustration which I went through.

Monday, February 2, 2009

Lets learn from my mistakes

How many times have you spend hours to fix a bug (technical jargon) and you know that it is something small you have missed that's causing this to fail only to realise later that it was some small thing you missed. Well, now that you have the solution for the small error you made, can you remember it for a later time? say an year or maybe even few months. Its not always that you remember the solution you implemented the last time you faced such an issue. So here I am trying to help you learn from MY mistakes :)
I will keep adding more as and when I come across more issues
  • 1
    IE behaves differently from Firefox when I put a rowspan
    Appaerntly IE disregards 'rowspan' as it expects the 's' in rowspan to be in upper case.
    So something that would work on both IE and Firefox is 'rowSpan'
  • 2
    When I put html in blogger html editor, for some reason it puts huge amount of spaces/breaks in it
    Convert line breaks is set to 'Yes'
    Go to Settings >> Formatting and make sure 'Convert line breaks' is set to 'No'
  • 3
    When I try to use xml.query in SQL for an attribute i keep getting the error "XQuery [query()]: Attribute may not appear outside of an element"
    There are certain limitations with accessing XML data type in SQL and the errors thrown are not really helpful in identifying what is the real issue. There are different ways to access value from a node and attribute.
    Use data() instead. I looked up on google and Matija Lah's post helped me resolve this. To access attributes use
    Select .query('data(@PubDate)').value('.','datetime') as PublishDate