Home > Articles

  • Print
  • + Share This

Using the Validator Ccontrols

When you are writing data entry forms for the web, you must often need to make certain that the form is filled out correctly. This would mean that certain fields are filled in, others are filled in, but with values that fit into a range, and so on. In the past, this was could either be done by writing code at either at the server or at the client. If the code is at the server, it might result in causing the information to be passed between the client and server needlessly. If you would rather place the code at the client, you run into the problem with cross-browser capabilities.

There are a number of Validator controls that come with Visual Basic.NET that make form validation much easier. The controls will either process the validation at the server, or at the client if the control determines that the browser is capable of it. There are five validation controls that are available in Visual Basic.NET:

  • RequiredFieldValidator – this control ensures that a field has been filled in. You can use it any time that you want to make certain that the user completes a form before submitting it.

  • CompareValidator – this control ensures either that two fields match, or how a field compares to some value. In the first case, this is useful when you want the user to enter their password twice. Comparing the field to some value would be useful if you wanted the user to enter a positive number, or if it is a particular type of information (for example, a date).

  • RangeValidator – this control ensures that the value entered in a field is within a range. The range could either be a two values (for example, a starting and ending date), or two controls. This is useful as part of a report, where you might want the user to select a date to display that is within the range of information stored in a database.

  • RegularExpressionValidator – this control ensures that the value entered "looks" like it should. The value is compared to a 'Regular Expression' (see note). If it matches, the value is considered valid. This can be useful for values that must have a certain structure, such as phone number, ISBN or part number entry fields.

  • CustomValidator – this control is the most flexible of the Validators. It allows you to add your own code to validate the field. This code could either run at the server, or on the client. This would be useful when one of the other validators does not fit your purpose, or valid information must be determined through some process – for example, if the value must be one of a number of entries that are in a database.

In addition to these five controls, there is also the ValidationSummary control. This control will display all of the error messages from all of the Validator controls on the same page. This is useful to provide a single location for all this information.

The five validation controls have a number of important properties in common. These relate to the control they monitor, and how the error is displayed. The most important of these properties are described in Table 10.4.

Table 10.4 Common properties for the validation controls

Property

Description

ControlToValidate

This is the most important property of all the validation controls. It should be set to point to another control (by name) on the same form. This is made easier, as you can simply use the drop-down in the Property window to select the monitored control.

ErrorMessage

This is the message to display if there is an error with the validator, for example, if the field is left blank. This should be enough information to allow the user to determine what is wrong, and how to fix their error.

Display

This is a rather odd property that defines how the validator control appears on the web page. By default, it is Static, however there are two other choices, Dynamic or None. If Static, it means that the space taken up by the ErrorMessage will always be taken up, even if the ErrorMessage is not being shown. This is useful if you want to guarantee how your web page will be laid out. Dynamic means that the control takes up no space until the ErrorMessage property is shown. This is useful if you don't want blank spaces on your form. Finally, if this property is set to None, the ErrorMessage will never be shown. This is really only useful in conjunction with the ValidationSummary (which will show the error).


We can use some of these controls to finish our Madlib sample application. We can use RequiredFieldValidator controls to ensure that the user has entered information in certain fields, and the RangeValidator to make certain that an appropriate number has been entered in the txtNumber field. Finally, we can summarize all errors with a ValidationSummary control.

Again, either copy the old project or form, or open the existing project to allow us to edit it. We'll add the Validator controls to this existing form.

Drag a RequiredFieldValidator next to each of the remaining TextBox controls (txtName, txtNumber, txtVerb and txtOccupation). Add a RangeValidator next to the RequiredFieldValidator you added to the txtNumber field. Finally, add a ValidationSummary control on a line of its own between the buttons and the lblResult control. Set the properties of each of these controls as shown in Table 10.5.

Table 10.5 Properties for the Validator controls

Control

Property

Value

RequiredFieldValidator

NameID

reqName

 

ControlToValidate

txtName

 

ErrorMessage

Please enter a name

RequiredFieldValidator

Name(ID)

reqNumber

 

ControlToValidate

txtNumber

 

ErrorMessage

Please enter a number

 

Display

Dynamic

RangeValidator

Name(ID)

rngNumber

 

ControlToValidate

txtNumber

 

ErrorMessage

Please enter a number between 100 and 1000

 

Display

Dynamic

 

Type

Integer

 

MaximumValue

1000

 

MinimumValue

100

RequiredFieldValidator

Name(ID)

reqVerb

 

ControlToValidate

txtVerb

 

ErrorMessage

Please enter a verb

 

Display

Dynamic

RequiredFieldValidator

Name(ID)

reqOccupation

 

ControlToValidate

txtOccupation

 

ErrorMessage

Please enter an occupation

 

Display

Dynamic

ValidationSummary

Name(ID)

valSummary


We should take a moment to describe the three properties of the RangeValidator we haven't discussed previously. While the MaximumValue and MinimumValue hopefully make sense in terms of something called a RangeValidator, the Type property is not so obvious. As the RangeValidator might be used to test a number of different types of values (integers, financial values, dates), the Type property identifies the type of information to compare. It can have one of the following values:

  • String the default, this causes the control to test if the value is alphabetically between the two extremes.

  • Integer compares the value to the two extremes to make certain that the value fits. Only Integer (whole)values are used.

  • Double the same as with Integer, but includes the decimal part of the value and extremes.

  • Currency the same as with Integer, but includes the first four decimals of the value.

  • DateTime compares the values as though they were dates, so August 27, 1964 would come between November 23, 1963 and April 1, 1986.

Now on to why the validator controls are so useful. To make them work, we don't have to add any additional code. Build and view the new web page (see Figure 10.7). Try leaving some fields blank, delete the 500 that is the default value for the number field. You should see red error messages appearing on the form. If not, try clicking the WriteStory Button. You should see something like what appears in Figure 10.8. Try entering a value outside of the range for the number field. Finally, enter in correct values for all the fields and select the WriteStory Button. All error messages should go away, and our story should be written.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020