Five favourite new features in VS 2008

1. Extension methods

This feature I like most.
Thanks that you can extend standard object methods

Lets look below example:

<br />public static class StringHelper {<br /> public static bool IsTrimmed (this string a) {<br /> return a.Trim().Equals(a);<br /> }<br />}<br />

As you noticed only difference is “this” word near parameter.
Here you are how to use this:

<br />string a = "abc ";<br />string b = "bcd";<br /><br />bool result1 = a.IsTrimmed(); // uses extenston<br />bool result2 = StringHelper.IsTrimmed(b) ; // standard call<br />


Please also note that if you add extension to object type – all variable types will get access to this extension!

My favourite example (coming from Scott Gu’s blog http://weblogs.asp.net/scottgu/archive/2007/03/13/new-orcas-language-feature-extension-methods.aspx )


<br />// Extension<br />public static bool In (this object o, System.Collections.IEnumerable c) {<br /> foreach( object i in c) {<br /> if (i.Equals(o)) return true;<br /> }<br /> return false;<br />};<br /><br /><br />// *** EXAMPLE ***<br /><br /><br />// search string array<br />bool result = "a".In( new string[] {"a","b","c"} );<br />Console.WriteLine(result );<br /><br />// search List<int><br />List <int> intVals = new List<int>();<br />intVals.Add(10);<br />intVals.Add(11);<br />intVals.Add(12);<br />intVals.Add(13);<br /><br />result = 13.In(intVals)<br />


2. Object Initializers

This is feature I waited long. It gives you possibility to assign in one line public properties in braces after constructor, like this:

<br /><br />TestClass tc = new TestClass() {Name="John", Surname = "Kowalsky"};<br /><br />public class TestClass {<br /> public string Name {<br /> get; set;<br /> }<br /> public string Surname {<br /> get; set;<br /> }<br />}<br />


3. Automatic Properties

If you don’t like all extra effort you need to do to write fields and properties code you can use below snippet.

<br /><br />public string Name {<br /> get;<br /> set;<br />}<br />

CLR 3.x (during compilation) will generate fields and property code for you.
Note: you will not be able to access generated field (only way is only through setters and getters)

4. Local variable type inference

This feature allows you define local variables without defining their types (similar to variant variables in some cases), so you can do this:


<br />var var1 = 10;<br />var var2 = “some string”;<br />var var3 = new SomeType();<br />

Compiler generates appropriate int, string and “SomeType” variables in early-bound strongly-typed fashion.

Personally, I’d prefer explicit types definitions – this gives more clarity in code.
But in some cases (mainly for shorten long code) I’m finding it usefull:

<br /><br />// Foreach<br />Foreach (var i in someCollection) <br /> …<br />// instead of Dictionary<int,> dictCol = new Dictionary<int,>();<br />var dictCol = new Dictionary<int,>();<br />

5. Lambdas

Described soon...




Other nice features:
- partial methods

Enable or Disable ScreenSaver in c#

Self-Explaining code snippet:

<br />private Microsoft.Win32.RegistryKey regkeyScreenSaver;<br />private object origScreenSaveSetting;<br /><br />void ResumeScreenSaver() {<br />// Reset screen saver to original setting<br />regkeyScreenSaver.SetValue("ScreenSaveActive", origScreenSaveSetting);<br />}<br />void TurnOffScreenSaver() {<br />// Get current screen saver setting<br />regkeyScreenSaver = Microsoft.Win32.Registry.CurrentUser.OpenSubKey("Control Panel").OpenSubKey("Desktop", true);<br />origScreenSaveSetting = regkeyScreenSaver.GetValue("ScreenSaveActive");<br /><br />//Turn screen saver off<br />regkeyScreenSaver.SetValue("ScreenSaveActive", "0");<br />}<br />

Best way to run external program

Sometime you might look the way to run external program from your C# application.
If so, you should interest Process.Start() method inside using System.Diagnostics namespace.

Below I'm presenting code snippets doing common task for us:

<br />// Example 1<br />//<br />// run external process and wait<br />Process proc = Process.Start("notepad.exe");<br />while (!proc.HasExited) {<br /> System.Windows.Forms.Application.DoEvents();<br />}<br /><br />// Example 2<br />//<br />// open C:\ folder in explorer<br />Process.Start("C:\\");<br /><br />// Example 3<br />//<br />// External program call wit parameters<br />// For the example<br />string dir1 = "C:\\Dir\\Temp";<br /><br />// Use ProcessStartInfo class<br />ProcessStartInfo startInfo = new rocessStartInfo();<br />startInfo.CreateNoWindow = false;<br />startInfo.UseShellExecute = false;<br />startInfo.FileName = "extApp.exe";<br />startInfo.WindowStyle = ProcessWindowStyle.Hidden;<br />startInfo.Arguments = " --input_dir \"" + dir1 + "\";<br /><br />// run process and release resources after finish (thanks to using statement)<br />try {<br /> using (Process exeProcess = Process.Start(startInfo)) {<br /> exeProcess.WaitForExit();<br /> }<br />}<br />catch {<br /> // Error here<br />}<br />

MS SQL 2005: Previous row value

SQL 2005 can number rows by command:
ROW_NUMBER() OVER (ORDER BY field_x,y…)

Another usefull 2205's command allowing "aliasing SQL" is:
WITH table_name AS ( SELECT … ) SELECT table_name ….

Command can be used for creating "virtual" (calcluated) columns


Below, snippet presenting how to archive previous row values in one SQL query.


<br />WITH [TEMP_TABLE] AS <br />( <br /> SELECT <br /> -- Create row number<br /> ROW_NUMBER() OVER (ORDER BY FUND_ID, DATE) AS 'ROW_ID',<br /> FUND_ID,DATE,CASH <br /> FROM CASH_PRO<br />)<br /> <br />-- Join <br />SELECT A.* , B.CASH AS 'PREV_CASH'<br /> FROM [TEMP_TABLE] AS A <br /> LEFT JOIN [TEMP_TABLE] AS B ON B.ROW_ID = (A.ROW_ID -1)<br />

Incremental sum in TSQL

I've required incremental sums in one SQL query.
There is my trick base on unique field which is ID in my case:

<br />SELECT r.ref_return,<br />(SELECT SUM(ref_return) FROM REFERENCES_RETURN WHERE id<= r.id) AS 'incr_sum'<br />FROM REFERENCES_RETURN r<br />