Fengying ASP. NET basic teaching 4 verification control

ArticleDirectory

• Causesvalidation = false
• Causesvalidation = true
• Type attribute
• Compare with a constant
• Comparison with other controls
• Client Verification Method
• You can also create a server-side verification method.

Preface

No matter what application system, its most essential function and purpose is to process data. In this way, data security becomes a very important topic in the system design, and some insecure data is submitted (such as SQL injection, data type, or inappropriate data range) this often leads to incorrect system computing results, paralysis, and even crash!

Therefore, this requires that the legitimacy of data must be verified when designing the system data entry and submission functions to ensure clean and accurate data flow into the system.

Anyone with web development experience knows that Javascript script verification is the most used for data input legality verification. This method is used to verify the validity of data input in the form field of a webpage using a JS script. If the input is incorrect, the data submission operation is terminated. This verification method does not occupy server resources and can ensure its performance. However, once the user disables the browser's Js script. Or, for an attacker proficient in this field, these methods are vulnerable (I can forge a page with only form fields, without JS verification scripts, and easily deal with them through high-tech (firebug ).

In the face of this situation, most developers began to use server-side verification methods. Although the server-side verification method is more secure for JS scripts, it will allow you to write a lot of verificationCode. No matter the amount of code or the consumption of server resources, too many verification logic is not ideal. Therefore, the data entry control on pages in ASPnet is. After the verification control is bound to the input control, the verification control automatically performs dual verification between the client and the server. What we do is to set the data verification rules in the verification space, and Related prompts. If the data entered on the corresponding page is blank, the type is incorrect, or the verification rules are not followed, the verification control completely terminates the page and returns the corresponding verification prompt.

Verify the control type

ASP. NET provides a total of six verification controls, such as the range check and pattern matching.

Requiredfieldvalidator	Non-empty Verification
Rangevalidataor	The user checks whether the data entered by the user is within the specified range. You can use it to check the range of numbers, letters, and dates.
Comparevalidataor	It can be used to check the comparison with specific data types of other controls (greater than, less than, or equal)
Regularexpressionvalidataor	Regular Expression Verification
Customvalidataor	Custom Verification
Validationsummary	It has no verification effect, but is often used with the verification control to Display error messages from all the verification controls on the web page.

Of course, not only one control can have one verification, but one control can be verified by multiple verification controls. For example, a text box can be used for both non-empty verification and regular expression verification.

Basevalidator

Basevalidator is the base class of all verification classes. It provides and implements all verification controls and its common attributes and methods.

Controltovalidate	Verify the programming ID of the input control that the control will calculate. If this is an invalid ID, an exception is thrown.
Display	None: The verification control is never displayed inline. If you want to display an error in the validationsummary control, you can use this item Static: If the verification fails, the error message is displayed. Even if the verification succeeds, the displayed space is occupied. Dynamic: If the verification fails, the error message is displayed. If the verification succeeds, the displayed space is not occupied.
Enableclientscript	Indicates whether to enable client verification. js verification can be disabled by setting this attribute to false.
Enable	Indicates whether to enable the verification effect if the control is flase.
Errormessage	Text displayed when verification error occursIt allows HTML information input.That is to say, we can write an IMG mark.
Forecolor	Text color displayed when verification error occurs
Isvalid	Whether the verified control has passed verification
Focusonerror	When a verification error occurs, retrieve the focus of the incorrect control.
Validationgroup	Specifies the verification group of the verification control.
Validate ()	Perform the verification operation and update the isvalid attribute
Text	If the error message displayed on the page is not specified, the error message is displayed.

Verification process

In ASP. net contains many data submission controls that can be sent back to the server, such as bulletedlist, button, checkbox, checkboxlist, htmlbutton, htmlinputbutton, htmlinputimage, imagebutton, linkbutton, ListBox, radiobuttonlist and textbox controls. These buttons all have a causesvalidation attribute.

Causesvalidation = false

ASPnet ignores the verification control, the page is normally sent back, and the event processing code is executed normally.

Causesvalidation = true

ASPnet will execute all the verification controls, and the data request will be sent back only when the verification is passed.

Before ignore

After ignore

It is worth noting that some controls can be sent back to the server only when their autopostback attribute is set to true.

Each of these controls has a validationgroup attribute. After this attribute is set, only the verification control in the specified group is verified when the control triggers server sending back.

The return control of the same group triggers events in the same group.

 

Requiredfieldvalidator

  1:     Asp: textbox   id   = "textbox1"   runat   =" server "  validationgroup   = "A"  >  Asp: textbox    

  2:     Asp: requiredfieldvalidator   id   = "requiredfieldvalidator1"   runat   =" server "  controltovalidate   = "textbox1"   display   = "dynamic"   errormessage   = "the account cannot be blank"   forecolor   =" red " >
     Asp: requiredfieldvalidator  > 

 

 

Rangevalidator

It can be used to verify whether user input data is within the specified range.

Type attribute

String	String Data Type
Integer	Specified as integer
Double	Double-precision floating point type
Date	Date data type
Currency	Currency type

 

Note: The range control does not verify non-null errors, so we prefer to use these two controls together. Prevents users from skipping the input of a control.

    Asp: rangevalidator   id   = "rangevalidator1"   runat   =" server "  controltovalidate   = "textbox1"   errormessage  =" & lt; IMG srcw.'a.jpg 'width = '20px '& gt; "  maximumvalue   =" 20 "  minimumvalue   =" 1 "  type   = "integer"  >  Asp: rangevalidator    

Comparevalidator

A comparison control requires at least one data entry control to verify the data.

We will use a comparison property operator.

Compare with a constant

 
<Asp: textbox id ="Textbox1"Runat ="Server"> </ASP: textbox>
 

<Asp: comparevalidator id ="Comparevalidator1"Runat ="Server"Errormessage ="Must be greater than 20"Valuetocompare ="20"Type ="Integer"Controltovalidate ="Textbox1" operator ="Equal"> </ASP: comparevalidator>
 

 
<Asp: button id ="Button1"Runat ="Server"TEXT ="Button"/>
 

Comparison with other controls

 
<Asp: textbox id ="Textbox1"Runat ="Server"> </ASP: textbox>
 

 
<Asp: textbox id ="Textbox2"Runat ="Server"> </ASP: textbox>
 

 
  
    "comparevalidator1"  runat = 
    "server"  errormessage = 
    "the data of the two controls must be consistent"  controltovalidate = 
    "textbox2"  controltocompare = 
   " textbox1 " operator = 
   " equal " 
   

 

Regularexpressionvalidator

You only need to specify the regular expression to be verified. The most common Verification

 

Custom verification control customvalidator

Generally, we use the verification control above to handle common data verification problems. If you do need custom verification methods. You can use customvalidator.

The custom verification control allows you to define the client and server verification sub-accounts based on your needs.Program. Then associate it with the verification control.

Client Verification Method

 
<Head Runat= "Server">
 

 
<Title> </Title>
 

 
<Script Type= "Text/JavaScript">
 

 
FunctionValidation1 (source, ARG ){
 

 
If(Arg. Value % 2 = 0)
 

 
Arg. isvalid =True;
 

Else
 

 
Arg. isvalid =False;
 

 
}
 

 
</Script>
 

 
</Head>
 

 
<Body>
 

 
<Form ID= "Form1" Runat= "Server">
 

 
<Div>
 

<ASP: textbox ID= "Textbox1" Runat= "Server"> </ASP: textbox>
 

 
<ASP: customvalidator ID= "Customvalidator1" Runat= "Server" Errormessage= "Cannot be divisible by 2" Clientvalidationfunction= "Validation1" Controltovalidate= "Textbox1"> </ASP: customvalidator>
 

Verification results

You can also create a server-side verification method.

 
 Protected VoidCustomvalidator1_servervalidate (ObjectSource, servervalidateeventargs ARGs)
 

 
{
 

Try
 

 
{
 

 
Args. isvalid =Int. Parse (ARGs. Value) % 2 = 0;
 

 
}
 

 
Catch(Exception)
 

 
{
 

 
Args. isvalid =False;
 

 
// Throw;
 

 
}
 

 
}
 

You only need to create a server-side verification event.

 

Page. isvalid

Note: If you want to determine whether the verification is successful in pageload, you need to call the page. Validate () method to check whether the verification is successful through the page. isvalid attribute.

If we only want to know whether the call is successful in a similar click event, we do not need to call the page. Validate () method.

You can see through the ASPNET page lifecycle that the verification occurs after the load event and before the Custom Event.

 

Summary

We have explained five common verification controls in ASPnet.

Next we will introduce the custom verification control.