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1 ASP.NET ASP.NET Rina Zviel-Girshin Lecture 3
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ASP.NETASP.NET
Rina Zviel-Girshin
Lecture 3
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Overview
Cookies Validation controls Client and server side validation Validation control examples
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Cookie
HTTP protocol is stateless – does not remember users or user’s actions.
Cookie is a small file embedded by server application on the user's computer.
The file is a text file, usually stored in directory named Cookies and having username@WebServerName[1].txt name.
Cookies are useful for storing nonessential data user preferences or choices.
Each time the same client requests a page the cookie is sent to the server.
The server checks cookie's value and perform some actions according to information stored in cookie.
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Cookies in ASP.NET
Exists class HttpCookie which provides a type-safe way to create and manipulate individual HTTP cookies.
Exist several constructors. A one argument constructor creates a cookie with a given
name. The object of the class has several properties. Some of
those are: Expires - gets or sets the expiration date and time for the
cookie. Values - gets a collection of key-and-value pairs that are
contained within a single cookie object. Items can be added to the collection using add(key,value) method.
Value - gets or sets an individual cookie value.
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Example- cookietest1.aspx
<%@ Page language="c#" Codebehind="cookietest1.aspx.cs" Inherits="cookie1.WebForm1" %>
<html><head><title>WebForm1</title></head>
<body MS_POSITIONING="GridLayout">
<form id="Form1" method="post" runat="server">
<asp:Label id="Label1" runat="server" Width="303px" Height="23px">Choose the language</asp:Label>
<asp:Button id="Button1" runat="server" Width="184px" Height="53px" Text="Remember"></asp:Button>
<asp:RadioButtonList id="RadioButtonList1" runat="server" Width="277px" Height="56px">
<asp:ListItem Value="VB" Selected="True">VB</asp:ListItem>
<asp:ListItem Value="CSharp">C#</asp:ListItem></asp:RadioButtonList>
</form></body></html>
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Output
Button
RadioButtonList
Label
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Codebehind- cookietest1.aspx.cs
using System;using System.Collections;using System.ComponentModel;using System.Data;using System.Drawing;using System.Web;using System.Web.SessionState;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.HtmlControls;
namespace cookie1{
public class WebForm1 : System.Web.UI.Page{
protected System.Web.UI.WebControls.Button Button1;protected System.Web.UI.WebControls.RadioButtonList
RadioButtonList1;
protected System.Web.UI.WebControls.Label Label1;
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Codebehind- cookietest1.aspx.cs (2)
private void Button1_Click(object sender, System.EventArgs e){if (Request.Cookies["language"] == null) { HttpCookie cookie = new HttpCookie("language");
cookie.Expires = DateTime.MaxValue; // never expirescookie.Value = RadioButtonList1.SelectedItem.Value;Response.Cookies.Add(cookie); //sends cookie to userButton1.Text="Show cookie";
}else { String str =Request.Cookies["language"].Value;
Label1.Text="All the examples will be shown using "+str;RadioButtonList1.Visible=false;Button1.Visible=false;
}}
} //end of class}//end of namespace
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Output
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Output from cookie
else {String str = Request.Cookies["language"].Value;Label1.Text="All the examples will be shown using " +str;RadioButtonList1.Visible=false;Button1.Visible=false;}
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Validation
Validation definitions: Tests to determine whether an implemented system
fulfills its requirements. The checking of data for correctness or for compliance
with applicable standards, rules, and or minimum requirements.
ASP.NET provides sophisticated validation mechanism that can be added to any page.
What do we want to validate? Usually a page data items entered or changed by the user.
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Validation process
Validation can be performed on client’s side or on server’s side or both.
A client-side validation requires writing a special script to check if user’s data is correct.
A server-side validation requires or writing a special server script to check the data or usage of the specially developed validation server
controls.
A good technique is to use both.
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Client-side validation
Reduces the number of round trips necessary, instant feedback to the user.
With a client-side validation errors are detected on the client side when the form is submitted to the server.
If any of the validators are found to be in error, the submission of the form to the server is cancelled and the validator's Text property is displayed.
This permits the user to correct the input before submitting the form to the server.
Written inside some script. Can be viewed by malicious user to enter bad data. Some browser can’t perform a required script.
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Server-side validators
Written inside a server script or server validation controls are used.
Information hiding, security and more.
Functions correctly in any browser (does not depend on client side - performed on server).
A server validation control is used to validate the data written of some input control.
The validation process is relatively simple If the data does not pass validation, it will display an error message
to the user. If the data passes validation continue to the next item/page/action.
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ASP.NET Validation Controls
ASP.NET validation controls automatically generate client-side and server-side code.
If a browser supports a client script language then a client-side validation script is sent to the browser.
If a browser incapable of supporting a client script language then a server validation script automatically implemented.
You can enable/disable client-side validation: Client-side validation is enabled by default.”uplevel”
validation. <%Page ClientTarget=“downlevel” %> -disables client-
side validation
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Adding Validation Control to the Page
Validation controls are added to a Web Forms page like any other server controls.
Exists several types of Validation controls: such as range checking or pattern matching, or a RequiredFieldValidator that ensures that a user does
not skip this field. You can attach more than one validation control to
one input control. For example
you might specify both that an entry is required and that it must contain a specific range of values.
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Input to validate
Validation controls work with a limited subset of HTML and Web server controls.
For each control, a specific property contains the value to be validated.
Some input controls and their validation property:1. HtmlInputText (Value) HtmlTextArea(Value)
HtmlSelect(Value) HtmlInputFile(Value) – where HTML means HTML control
2. TextBox(Text) ListBox(SelectedItem.Value) DropDownList (SelectedItem.Value) RadioButtonList (SelectedItem.Value)
HTML controls
Web-server controls
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Types of Validation Controls
There are 5 types of individual validation controls in ASP.NET: RequiredFieldValidator CompareValidator RangeValidator RegularExpressionValidator CustomValidator
Also exists a ValidationSummary control that gathers all ErrorMessages and displays them using a bulleted list, a plain list or a single paragraph format.
Each control has a specific action to perform.
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Syntax
A basic syntax for creating a validation control is:
<asp:control_name id="some_id"
ControlToValidate ="some_cnt" runat="server" /> A more complex syntax specifies more properties:
<asp:control_name id="some_id"
ControlToValidate ="some_cnt" Display=“value”
Text=“some text” ErrorMessage=“message” runat="server" /> Display property values can be:
static (default - may be hidden but requires a span display), dynamic (span with none or inline display) and none (no error message).
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RequiredFieldValidator
A RequiredFieldValidator is the simplest form of validation.
It makes some input a required field - ensures that the user does not skip this entry. If the user enters any value in a field (even gibberish) it is valid.
The validation fails if the input value does not change from its initial value (InitialValue property). By default the InitialValue is an empty string ("").
If all of the fields in the page are valid, the page is valid.
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Example
<html><body><form runat="server">Name: <asp:TextBox id="name" runat="server" /><br />Age: <asp:TextBox id="age" runat="server" /><br /><br /><asp:Button runat="server" Text="Submit" /><br /><br /><asp:RequiredFieldValidator ControlToValidate="name"Text="The name field is required!“ runat="server" /></form></body></html>
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RangeValidator A RangeValidator control is used to check that the user
enters an input value that falls between two values (a given range).
It is possible to check ranges within numbers, dates and characters.
ControlToValidate contains name of the control to be validated.
MinimumValue and MaximumValue define the minimum and maximum values of the valid range.
Type property specifies the data type of the value to check. Currency, Date/Time, Double, Integer or String.
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Example
<html><body><form runat="server">Enter a date between 2005-01-01 and 2005-12-31:<br /><asp:TextBox id="tb" runat="server" /><br /><br /><asp:Button Text="Submit" runat="server" /><br /><br /><asp:RangeValidator ControlToValidate="tb"MinimumValue="2005-01-01" MaximumValue="2005-12-31"Type="Date" EnableClientScript="false"Text="The date must be between 2005-01-01 and 2005-12-31!"runat="server" /></form></body></html>
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CompareValidator Compares the value of one input control to the value of
another input control or to a fixed value. A CompareValidator uses three key properties to
perform its validation. ControlToValidate and ControlToCompare (or
ValueToCompare) containing the values to compare Operator defines the type of comparison to perform
for example: Equal or Not Equal, LessThan or GreaterThanEqual A Type property of the control is defined as in
RangeValidator. If the expression evaluates true, the validation result is
valid.
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Example
<html><body><form runat="server"><table border="0" bgcolor="#b0c4de"> <tr valign="top"><td colspan="4"><h4>Compare two values</h4></td> </tr><tr valign="top">
<td><asp:TextBox id="txt1" runat="server"/></td> <td> = </td> <td><asp:TextBox id="txt2" runat="server"/> </td>
<td><asp:Button Text="Validate" runat="server" /></td> </tr></table><br /><asp:CompareValidator id="compval“ Display="dynamic"ControlToValidate="txt1“ ControlToCompare="txt2" ForeColor="red“ BackColor="yellow" Type="String“ EnableClientScript="false" Text="Validation Failed!" runat="server" /></form></body></html>
STYLE Why no operator = value given?
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Output
ForeColor="red“ BackColor="yellow" Text="Validation Failed!"
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Example: a fix value validation
<%@ Page Language="C#"%>
<script runat=“server”>
void Button_Click(Object sender, EventArgs e)
{Response.Redirect( "ThankYou.aspx" );}
</script>
<html><body><form Runat="Server">
Minimum Bid: $2,000<br/>
Enter your bid: <asp:TextBox id="Amount" Columns="8" Runat="Server"/>
<asp:CompareValidator ControlToValidate="Amount"
ValueToCompare="2,000" Display="Dynamic"
Text="Your bid must be greater than the minimum bid!"
Operator="GreaterThan" Type="Currency" Runat="Server" />
<p><asp:Button Text="Submit" OnClick="Button_Click" Runat="Server"/>
</form></body></html>
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CustomValidator Allows you to write a method to handle the validation
of the value entered calls a user-defined function to perform validations.
A user defined function can be executed in the server or in client-side script.
OnServerValidate property specifies the name of the server-side validation script function to be executed.
ClientValidationFunction property specifies the name of the client-side validation script function to be executed type FunctionName (source, arguments)
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Example a spaghetti-like code
<script runat="server">void user(object source, ServerValidateEventArgs args ) { if (args.Value.length<8 || args.Value.length>18)
args.IsValid=false else args.IsValid=true }</script>
<html><body><form runat="server"><asp:Label runat="server" Text="Enter a username: " /><asp:TextBox id="txt1" runat="server" /><asp:Button Text="Submit" runat="server"/><br /><asp:CustomValidator ControlToValidate="txt1"OnServerValidate="user" Text="A username must be between 8 and 18 characters!" runat="server"/>
</form></body></html>
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Output
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RegularExpressionValidator
A RegularExpressionValidator control is used to ensure that an input value matches a specified pattern, called a regular expression.
Both server- and client-side validation are performed unless the browser does not support the client-side validation or the EnableClientScript property is set to false.
ValidationExpression property specifies the expression used to validate an input control.
The regular expression is a string and therefore is written between quotes.
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Regular Expressions
Some basic regular expressions: "[a-z]" validates all characters of the alphabet "[^a-z]" validates all characters that is not in the alphabet “[abcd]” a “character class” - means a or b or c or d “.” means any character except a newline “r*” - means repetition of r 0 or more times “a?” means zero or one a’s "[0-9]" validates all numeric characters "[^0-9]" valid all non-numeric characters "\d" validates a numeric character
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Regular Expressions cont.
Some basic regular expressions: "\n" validates a line break "\t" validates a tabulation "\s" validates all blank character (line break, space,
tabulation) "\." is for displaying the point "^" is for being at the beginning of the line "$" is for being at the end of the line (so "^$" is an empty
string) “a{1,3}” - means from one to three a’s “rs” – means r concatenated with s
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Examples
“[1-9][0-9]*” validates integer constants “[^0-9\n]” validates any letter except upper case
letters or a new-line "zo{2}" validates "zoo“ "zo*" validates "z“, “zo” and "zoo" (one character
followed by * is valid if this character is present 0 or n times)
"zo{1,2}" validates "zo" and "zoo“ "do(es)?" validates "do" or "does"
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More complicated expressions
An email validation (pattern : [email protected]) ".*@.*\..*"
A five digits postal code will be validated by "^\d{5}$“
A phone number will be validated by (bezeq) "^0[2-48-9]-\d{7}$"
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Partial Example
Enter an email:
<input type="text" id=“email" size="40" runat="server" />Tip: enter a valid email address<asp:RegularExpressionValidator id="valRegExpr" ControlToValidate=“email“ runat="server"ValidationExpression=".*@.*\..*"ErrorMessage="* Your entry does not match the correct email syntax“ Display="dynamic">*
</asp:RegularExpressionValidator>
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IsValid property
After all validation controls have been processed, the IsValid property on the page is set. If any of the controls shows that a validation check failed,
the entire page is set to be invalid.
If a validation control is in error, an error message may be displayed in the page by that validation control or in a ValidationSummary control elsewhere on the page.
The ValidationSummary control is displayed when the IsValid property of the page is false.
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ValidationSummary
The ValidationSummary control is used to display a summary of all validation errors occurred in a Web page.
The error message displayed in this control is specified by the ErrorMessage property of each validation control.
If an ErrorMessage property of the validation control is not set - no error message is displayed for that validation control.
DisplayMode property can be one of the BulletList, List or SingleParagraph
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Example
<html><body><form runat="server"><table><tr><td><table bgcolor="#b0c4de" cellspacing="10"> <tr> <td align="right">Name:</td> <td><asp:TextBox id=“tb" runat="server"/></td> <td> <asp:RequiredFieldValidator Text="*"
ControlToValidate=“tb" ErrorMessage="Name“ runat="server"/> </td> </tr> <tr> <td align="right">Card Type:</td> <td><asp:RadioButtonList id="rbl" RepeatLayout="Flow“ runat="server">
<asp:ListItem>Diners</asp:ListItem><asp:ListItem>MasterCard</asp:ListItem> </asp:RadioButtonList></td>
<td> <asp:RequiredFieldValidator ControlToValidate="rbl" InitialValue=" " ErrorMessage="Card Type" Text="*" runat="server"/> </td> </tr> <tr> <td></td> <td><asp:Button id="b1" Text="Submit“ runat="server"/> </td> <td></td> </tr></table>
<asp:ValidationSummaryHeaderText="You must enter a value in the following fields:"DisplayMode="BulletList“ EnableClientScript="true“ runat="server"/></form></body></html>
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Output
<asp:ValidationSummaryHeaderText="You must enter a value in the following fields:"DisplayMode="BulletList“ EnableClientScript="true“ runat="server"/>
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Events in .NET
There are hundreds events in .NET. Some are user depended
clicks, selections, changing values, and some are generated by ASP.NET itself
database item inserted into DataGrid. The user depended events can be divided into two types: Postback Events - immediately reported to the Web server
via a form submission buttons, hyperlinks
Non-Postback Events - the browser takes note of but doesn't report until the next form submission
checkbox, radio button and list selections, text entries
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Any Questions?
