TemplateField Constructor ()

 

Initializes a new instance of the TemplateField class.

Namespace:   System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

Public Sub New

Use this constructor to initialize a new instance of the TemplateField class. This constructor is commonly used when adding fields to a dynamically created data-bound control.

To dynamically add a TemplateField object to a data-bound control, create a new TemplateField object, define the appropriate templates, and then add it to the data-bound control's field collection. For example, if you are using the GridView control, add the TemplateField object to the Columns collection.

System_CAPS_noteNote

Although you can dynamically add fields to a data-bound control, it is strongly recommended that fields be statically declared and then shown or hidden, as appropriate. Statically declaring all your fields reduces the size of the view state for the parent data-bound control.

The following code example demonstrates how to use the constructor to dynamically add a TemplateField field column to a GridView control.


<%@ Page language="VB" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  ' Create a template class to represent a dynamic template column.
  Public Class GridViewTemplate   
    Implements ITemplate

    Private templateType As DataControlRowType
    Private columnName As String

    Sub New(ByVal type As DataControlRowType, ByVal colname As String)

      templateType = type
      columnName = colname

    End Sub

    Sub InstantiateIn(ByVal container As System.Web.UI.Control) _
      Implements ITemplate.InstantiateIn

      ' Create the content for the different row types.
      Select Case templateType

        Case DataControlRowType.Header
          ' Create the controls to put in the header
          ' section and set their properties.
          Dim lc As New Literal
          lc.Text = "<b>" & columnName & "</b>"

          ' Add the controls to the Controls collection
          ' of the container.
          container.Controls.Add(lc)

        Case DataControlRowType.DataRow
          ' Create the controls to put in a data row
          ' section and set their properties.
          Dim firstName As New Label
          Dim lastName As New Label

          Dim spacer = New Literal
          spacer.Text = " "

          ' To support data binding, register the event-handling methods
          ' to perform the data binding. Each control needs its own event
          ' handler.
          AddHandler firstName.DataBinding, AddressOf FirstName_DataBinding
          AddHandler lastName.DataBinding, AddressOf LastName_DataBinding

          ' Add the controls to the Controls collection
          ' of the container.
          container.Controls.Add(firstName)
          container.Controls.Add(spacer)
          container.Controls.Add(lastName)

          ' Insert cases to create the content for the other 
          ' row types, if desired.

        Case Else

          ' Insert code to handle unexpected values. 

      End Select

    End Sub

    Private Sub FirstName_DataBinding(ByVal sender As Object, ByVal e As EventArgs)

      ' Get the Label control to bind the value. The Label control
      ' is contained in the object that raised the DataBinding 
      ' event (the sender parameter).
      Dim l As Label = CType(sender, Label)

      ' Get the GridViewRow object that contains the Label control. 
      Dim row As GridViewRow = CType(l.NamingContainer, GridViewRow)

      ' Get the field value from the GridViewRow object and 
      ' assign it to the Text property of the Label control.
      l.Text = DataBinder.Eval(row.DataItem, "au_fname").ToString()

    End Sub

    Private Sub LastName_DataBinding(ByVal sender As Object, ByVal e As EventArgs)

      ' Get the Label control to bind the value. The Label control
      ' is contained in the object that raised the DataBinding 
      ' event (the sender parameter).
      Dim l As Label = CType(sender, Label)

      ' Get the GridViewRow object that contains the Label control.
      Dim row As GridViewRow = CType(l.NamingContainer, GridViewRow)

      ' Get the field value from the GridViewRow object and 
      ' assign it to the Text property of the Label control.
      l.Text = DataBinder.Eval(row.DataItem, "au_lname").ToString()

    End Sub

  End Class

  Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

    ' The field columns need to be created only when the page is
    ' first loaded. 
    If Not IsPostBack Then
      ' Dynamically create field columns to display the desired
      ' fields from the data source. Create a TemplateField object 
      ' to display an author's first and last name.
      Dim customField As New TemplateField

      ' Create the dynamic templates and assign them to
      ' the appropriate template property.
      customField.ItemTemplate = New GridViewTemplate(DataControlRowType.DataRow, "Author Name")
      customField.HeaderTemplate = New GridViewTemplate(DataControlRowType.Header, "Author Name")

      ' Add the field column to the Columns collection of the
      ' GridView control.
      AuthorsGridView.Columns.Add(customField)
    End If

  End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>TemplateField Constructor Example</title>
</head>
<body>
    <form id="form1" runat="server">

      <h3>TemplateField Constructor Example</h3>

      <asp:gridview id="AuthorsGridView" 
        datasourceid="AuthorsSqlDataSource" 
        autogeneratecolumns="False"
        runat="server">                
      </asp:gridview>

      <!-- This example uses Microsoft SQL Server and connects -->
      <!-- to the Pubs sample database.                        -->
      <asp:sqldatasource id="AuthorsSqlDataSource"  
        selectcommand="SELECT [au_fname], [au_lname] FROM [authors]"
        connectionstring="server=localhost;database=pubs;integrated security=SSPI"
        runat="server">
      </asp:sqldatasource>

    </form>
  </body>
</html>

.NET Framework
Available since 2.0
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