Home > Articles > Programming > Windows Programming

This chapter is from the book

This chapter is from the book

Data Binding

Several of the built-in Dynamic Data field templates, including the DateTime and DateTime_Edit templates, rely on data binding to display column value on the page.

<asp:TextBox ID="textBox" runat="server" Text='<%# FieldValueEditString %>' />

In addition, the field template controls themselves are data bound, and several properties of the FieldTemplateUserControl base class rely on the data binding mechanics. These properties can be used safely only from the DataBind method and will throw an InvalidOperationException when used outside of the data binding context, such as during a post-back:

  • Row provides access to the entity instance the field template is bound to, such as an Order object. In Read-only and Edit modes, it is an equivalent of calling the Page.GetDataItem method. In Insert mode, this property returns a CustomTypeDescriptor object that provides access to default field values extracted by the page template from the page request URL (more on this in Chapter 6, “Page Templates”).
  • FieldValue returns value of the column property, such as Order.OrderDate. It is an equivalent of calling DataBinder.Eval(Row, Column.Name).
  • FieldValueString converts the field value to a display string in Read-only mode, using the formatting options specified in the data model or page markup. It is an equivalent of calling FormattingOptions.FormatValue(FieldValue).
  • FieldValueEditString converts the field value to a string in Edit or Insert mode, using the formatting options specified in the data model or page markup. It is an equivalent of calling FormattingOptions.FormatEditField(FieldValue).

During a post-back, a field template itself does not actually save the new column value back in its Row object. Instead, the FieldTemplateUserControl class implements the IBindableControl interface and relies on the parent FormView, DetailsView, and GridView controls to perform this task. When the parent control is handling an Insert or an Update command, it iterates through the list of its child controls and calls the ExtractValues of each child that implements IBindableControl interface.

protected override void ExtractValues(IOrderedDictionary dictionary)
  dictionary[this.Column.Name] =

The ExtractValues method receives a dictionary object used to store column name and value pairs. The extract from the DateTime_Edit field template just shown is a typical implementation of this method. The ConvertEditedValue method is provided by the FieldTemplateUserControl base class. It can automatically convert the field value to null based on the ConvertEmptyStringToNull and NullDisplayText formatting options.

Notice that by providing the dictionary argument, ExtractValue method allows a field template to return values of other columns or even multiple column values. This capability is important for the foreign key templates used for navigation properties, such as the Customer property of the Order class in the Northwind data model, that need to return values of the corresponding primitive properties, such as CustomerID. Consider Listing 3.9, which shows the markup of the ForeignKey_Edit template.

Listing 3.9. ForeignKey_Edit Field Template (Markup)

<%@ Control Language="C#" CodeBehind="ForeignKey_Edit.ascx.cs"
  Inherits="WebApplication.DynamicData.FieldTemplates.ForeignKey_EditField" %>

<asp:DropDownList ID="dropDownList" runat="server"/>

<asp:RequiredFieldValidator runat="server" ID="requiredFieldValidator"
  ControlToValidate="dropDownList" Enabled="false" />
<asp:DynamicValidator runat="server" ID="dynamicValidator"
  ControlToValidate="dropDownList" />

Notice that the ForeignKey_Edit template uses a DropDownList control, which allows users to select from a list of items created programmatically, in the Page_Load method shown in Listing 3.10. Each ListItem object in the DropDownList represents a single foreign key, with Text property storing value of the display column from the referenced table and Value property storing a comma-separated list of its primary key columns. This code relies on the convenience method, called PopulateListControl, provided by the FieldTemplateUserControl base class, which does all the heavy lifting required to query the referenced table, create the ListItem objects, and add them to the DropDownList.

Listing 3.10. ForeignKey_Edit Field Template (Code-Behind)

using System;
using System.Collections.Specialized;
using System.Web.DynamicData;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace WebApplication.DynamicData.FieldTemplates
  public partial class ForeignKey_EditField : FieldTemplateUserControl
    public override Control DataControl
      get { return this.dropDownList; }

    protected void Page_Load(object sender, EventArgs e)
      if (this.dropDownList.Items.Count == 0)
        if (this.Mode == DataBoundControlMode.Insert || !this.Column.IsRequired)
          this.dropDownList.Items.Add(new ListItem("[Not Set]", string.Empty));


    protected override void OnDataBinding(EventArgs e)
      string selectedValueString = this.GetSelectedValueString();
      if (this.dropDownList.Items.FindByValue(selectedValueString) != null)
        this.dropDownList.SelectedValue = selectedValueString;
    protected override void ExtractValues(IOrderedDictionary dictionary)
      this.ExtractForeignKey(dictionary, this.dropDownList.SelectedValue);

To display the current field value, the ForeignKey_Edit template cannot rely on the FieldValueEditString property because the FieldValue in this case consists of one or more values of the underlying primitive columns. For the Customer column of the Order table, this would mean displaying CustomerID, “ALFKI”, instead of the Customer’s CompanyName, “Alfreds Futterkiste”, which is not very user friendly. Instead, the ForeignKey_Edit template overrides the OnDataBinding method to select the matching item in the DropDownList. It calls the GetSelectedValueString, a convenience method provided by the FieldTemplateUserControl base class. For foreign key columns, this method is equivalent to calling ForeignKeyColumn.GetForeignKeyString(Row) and returns a comma-separated list of values of the primitive columns in the foreign key.

The ForeignKey_Edit template also overrides the ExtractValues method and calls the ExtractForeignKey provided by the FieldTemplateUserControl base class. Given a comma-separated list of column values, this method stores them in the dictionary under the names of the foreign key columns. Under the hood, this method simply calls ForeignKeyColumn.ExtractForeignKey(dictionary, selectedValue).

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.


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.


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.


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.


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


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


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.


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.


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