TemplateField Constructor
Definitie
Belangrijk
Bepaalde informatie heeft betrekking op een voorlopige productversie die aanzienlijk kan worden gewijzigd voordat deze wordt uitgebracht. Microsoft biedt geen enkele expliciete of impliciete garanties met betrekking tot de informatie die hier wordt verstrekt.
Initialiseert een nieuw exemplaar van de TemplateField klasse.
public:
TemplateField();public TemplateField();Public Sub New ()Voorbeelden
In het volgende codevoorbeeld ziet u hoe u de constructor gebruikt om dynamisch een TemplateField veldkolom aan een GridView besturingselement toe te voegen.
<%@ Page language="C#" %>
<!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 : ITemplate
{
private DataControlRowType templateType;
private string columnName;
public GridViewTemplate(DataControlRowType type, string colname)
{
templateType = type;
columnName = colname;
}
public void InstantiateIn(System.Web.UI.Control container)
{
// Create the content for the different row types.
switch(templateType)
{
case DataControlRowType.Header:
// Create the controls to put in the header
// section and set their properties.
Literal lc = new Literal();
lc.Text = "<b>" + columnName + "</b>";
// Add the controls to the Controls collection
// of the container.
container.Controls.Add(lc);
break;
case DataControlRowType.DataRow:
// Create the controls to put in a data row
// section and set their properties.
Label firstName = new Label();
Label lastName = new Label();
Literal 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.
firstName.DataBinding += new EventHandler(this.FirstName_DataBinding);
lastName.DataBinding += new EventHandler(this.LastName_DataBinding);
// Add the controls to the Controls collection
// of the container.
container.Controls.Add(firstName);
container.Controls.Add (spacer);
container.Controls.Add(lastName);
break;
// Insert cases to create the content for the other
// row types, if desired.
default:
// Insert code to handle unexpected values.
break;
}
}
private void FirstName_DataBinding(Object sender, EventArgs e)
{
// Get the Label control to bind the value. The Label control
// is contained in the object that raised the DataBinding
// event (the sender parameter).
Label l = (Label)sender;
// Get the GridViewRow object that contains the Label control.
GridViewRow row = (GridViewRow)l.NamingContainer;
// 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();
}
private void LastName_DataBinding(Object sender, EventArgs e)
{
// Get the Label control to bind the value. The Label control
// is contained in the object that raised the DataBinding
// event (the sender parameter).
Label l = (Label)sender;
// Get the GridViewRow object that contains the Label control.
GridViewRow row = (GridViewRow)l.NamingContainer;
// 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();
}
}
void Page_Load(Object sender, EventArgs e)
{
// The field columns need to be created only when the page is
// first loaded.
if (!IsPostBack)
{
// 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.
TemplateField customField = 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);
}
}
</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>
<%@ 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>
Opmerkingen
Gebruik deze constructor om een nieuw exemplaar van de TemplateField klasse te initialiseren. Deze constructor wordt vaak gebruikt bij het toevoegen van velden aan een dynamisch gemaakt gegevensgebonden besturingselement.
Als u een TemplateField object dynamisch wilt toevoegen aan een gegevensgebonden besturingselement, maakt u een nieuw TemplateField object, definieert u de juiste sjablonen en voegt u het vervolgens toe aan de veldverzameling van het gegevensgebonden besturingselement. Als u bijvoorbeeld het GridView besturingselement gebruikt, voegt u het TemplateField object toe aan de Columns verzameling.
Note
Hoewel u dynamisch velden aan een gegevensgebonden besturingselement kunt toevoegen, wordt het sterk aanbevolen dat velden statisch worden gedeclareerd en vervolgens indien van toepassing worden weergegeven of verborgen. Door al uw velden statisch te declareren, wordt de weergavestatus voor het bovenliggende besturingselement voor gegevens beperkt.
