TemplateField Costruttore
Definizione
Importante
Alcune informazioni sono relative alla release non definitiva del prodotto, che potrebbe subire modifiche significative prima della release definitiva. Microsoft non riconosce alcuna garanzia, espressa o implicita, in merito alle informazioni qui fornite.
Inizializza una nuova istanza della classe TemplateField.
public:
TemplateField();public TemplateField ();Public Sub New ()Esempio
Nell'esempio di codice seguente viene illustrato come usare il costruttore per aggiungere dinamicamente una TemplateField colonna di campo a un GridView controllo .
<%@ 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>
Commenti
Utilizzare questo costruttore per inizializzare una nuova istanza della TemplateField classe . Questo costruttore viene comunemente usato quando si aggiungono campi a un controllo associato a dati creato in modo dinamico.
Per aggiungere dinamicamente un TemplateField oggetto a un controllo associato a dati, creare un nuovo TemplateField oggetto, definire i modelli appropriati e quindi aggiungerlo alla raccolta di campi del controllo associato a dati. Ad esempio, se si usa il GridView controllo , aggiungere l'oggetto TemplateField alla Columns raccolta.
Nota
Sebbene sia possibile aggiungere in modo dinamico campi a un controllo associato a dati, è consigliabile dichiarare staticamente i campi e quindi visualizzati o nascosti, in base alle esigenze. La dichiarazione statica di tutti i campi riduce le dimensioni dello stato di visualizzazione per il controllo associato a dati padre.
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