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Tuesday, May 29, 2007

Imporve Performance Of Web Site

1. Maintain the position of the scrollbar on postbacks: In ASP.NET 1.1 it was a pain to maintain the position of the scrollbar when doing a postback operation. This was especially true when you had a grid on the page and went to edit a specific row. Instead of staying on the desired row, the page would reload and you'd be placed back at the top and have to scroll down.

2. Set the default focus to a control when the page loads: This is another extremely simple thing that can be done without resorting to writing JavaScript. If you only have a single textbox (or two) on a page why should the user have to click in the textbox to start typing? Shouldn't the cursor already be blinking in the textbox so they can type away? Using the DefaultFocus property of the HtmlForm control you can easily do this.

3. Set the default button that is triggered when the user hits the enter key: This was a major pain point in ASP.NET 1.1 and required some JavaScript to be written to ensure that when the user hit the enter key that the appropriate button on the form triggered a "click" event on the server-side. Fortunately, you can now use the HtmlForm control's DefaultButton property to set which button should be clicked when the user hits enter. This property is also available on the Panel control in cases where different buttons should be triggered as a user moves into different Panels on a page.

4. Validation groups: You may have a page that has multiple controls and multiple buttons. When one of the buttons is clicked you want specific validator controls to be evaluated rather than all of the validators defined on the page. With ASP.NET 1.1 there wasn't a great way to handle this without resorting to some hack code. ASP.NET 2.0 adds a ValidationGroup property to all validator controls and buttons (Button, LinkButton, etc.) that easily solves the problem. If you have a TextBox at the top of a page that has a RequiredFieldValidator next to it and a Button control, you can fire that one validator when the button is clicked by setting the ValidationGroup property on the button and on the RequiredFieldValidator to the same value. Any other validators not in the defined ValidationGroup will be ignored when the button is clicked.

Monday, May 28, 2007

String Functions in .NET

Several built-in string functions perform string manipulations to augment simple concatenation with the "&" operator.

Function in ASP.NET

Asc() Returns the character code of the first character of a string.

Asc("A") returns 65.

Chr() Returns the display character of a character code.

Chr(65) returns "A".

GetChar() Returns the character at a specified position in a string, counting from 1.

GetChar("This is a string", 7) returns "s".

InStr() Returns the starting position in a string of a substring, counting from 1.

InStr("This is a string", "string") returns 11.

InStrRev() Returns the starting position in a string of a substring, searching from the end of the string.

InStr("This is a string", "string") returns 11.

LCase() Returns the lower-case conversion of a string.

LCase("THIS IS A STRING") returns "this is a string".

Left() Returns the left-most specified number of characters of a string.

Left("This is a string", 4) returns "This".

Len() Returns the length of a string.

Len("This is a string") returns 16.

LTrim() Removes any leading spaces from a string.

LTrim(" This is a string") returns "This is a string".

Mid() Returns a substring from a string, specified as the starting position (counting from 1) and the number of characters.

Mid("This is a string", 6, 4) returns "is a".

Replace() Replaces all occurences of a substring in a string.

Replace("This is a string", " s", " longer s") returns "This are a longer string" (replaces an "s" preceded by a blank space).

Right() Returns the right-most specified number of characters of a string.

Right("This is a string", 6) returns "string".

RTrim() Removes any trailing spaces from a string.

RTrim("This is a string ") returns "This is a string".

Str() Returns the string equivalent of a number.

Str(100) returns "100".

Space() Fills a string with a given number of spaces.
"This" & Space(5) & "string" returns "This string".

StrComp() Compares two strings. Return values are 0 (strings are equal), 1 (first string has the greater value), or -1 (second string has the greater value) based on sorting sequence.

StrComp("This is a string", "This string") returns -1.

StrReverse() Reverses the characters in a string.

StrReverse("This is a string") returns "gnirts a si sihT".

Trim() Removes any leading and trailing spaces from a string.

Trim(" This is a string ") returns "This is a string".

UCase() Returns the upper-case conversion of a string.

UCase("This is a string") returns "THIS IS A STRING".

Val() Converts a numeric expression to a number.

Val( (1 + 2 + 3)^2 ) returns 36.

Mathematical Functions in .NET

Popular mathematical functions are summarized in the following table. Note that certain functions do not require the Math. prefix.

Mathematical Function in .NET

Math.Abs() Returns the absolute value.

Math.Abs(-10) returns 10.

Math.Ceiling() Returns an integer that is greater than or equal to a number.

Math.Ceiling(5.333) returns 6.

Fix() Returns the integer portion of a number.

Fix(5.3333) returns 5.

Math.Floor() Returns an integer that is less than or equal to a number.

Fix(5.3333) returns 5.

Int() Returns the integer portion of a number.

Int(5.3333) returns 5.

Math.Max() Returns the larger of two numbers.

Math.Max(5,7) returns 7.

Math.Min() Returns the smaller of two numbers.

Math.Min(5,7) returns 5.

Math.Pow() Returns a number raised to a power.

Math.Pow(12,2) returns 144.

Rnd() Returns a random number between 0 and 1. Used in conjunction with Randomizestatement to initialize the random number generator.

Math.Round() Rounds a number to a specified number of decimal places. Rounds up on .5.

Math.Round(1.1234567,5) returns 1.12346.

Math.Sign() Returns the sign of a number. Returns -1 if negative and 1 if positive.

Math.Sign(-5) returns -1.

Math.Sqrt() Returns the square root of a positive number.

Math.Sqrt(144) returns 12.