ImageField 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 ImageField.
public:
ImageField();public ImageField ();Public Sub New ()Esempio
Nell'esempio seguente viene illustrato come utilizzare questo costruttore per aggiungere dinamicamente un ImageField oggetto all'insieme Columns di 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">
void Page_Load(Object sender, EventArgs e)
{
if (!IsPostBack)
{
// Dynamically create a GridView control.
GridView employeesView = new GridView();
employeesView.ID = "EmployeesGrid";
employeesView.AutoGenerateColumns = false;
employeesView.DataSourceID = "EmployeeSource";
// Dynamically create field columns to display the desired
// fields from the data source.
// Create an ImageField object to display an employee's photo.
ImageField photoImageField = new ImageField();
photoImageField.DataImageUrlField = "PhotoPath";
photoImageField.AlternateText = "Employee Photo";
photoImageField.NullDisplayText = "No image on file.";
photoImageField.HeaderText = "Photo";
photoImageField.ReadOnly = true;
// Create a BoundField object to display an employee's last name.
BoundField lastNameBoundField = new BoundField();
lastNameBoundField.DataField = "LastName";
lastNameBoundField.HeaderText = "Last Name";
// Create a BoundField object to display an employee's first name.
BoundField firstNameBoundField = new BoundField();
firstNameBoundField.DataField = "FirstName";
firstNameBoundField.HeaderText = "First Name";
// Add the field columns to the Fields collection of the
// GridView control.
employeesView.Columns.Add(photoImageField);
employeesView.Columns.Add(lastNameBoundField);
employeesView.Columns.Add(firstNameBoundField);
// Add the GridView control to the Controls collection
// of the PlaceHolder control.
GridViewPlaceHolder.Controls.Add(employeesView);
}
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>ImageField Constructor Example</title>
</head>
<body>
<form id="form1" runat="server">
<h3>ImageField Constructor Example</h3>
<asp:placeholder id="GridViewPlaceHolder"
runat="server"/>
<!-- This example uses Microsoft SQL Server and connects -->
<!-- to the Northwind sample database. Use an ASP.NET -->
<!-- expression to retrieve the connection string value -->
<!-- from the Web.config file. -->
<asp:sqldatasource id="EmployeeSource"
selectcommand="Select [EmployeeID], [LastName], [FirstName], [PhotoPath] From [Employees]"
connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>"
runat="server"/>
</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">
Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
If Not IsPostBack Then
' Dynamically create a GridView control.
Dim employeesView As GridView = New GridView()
employeesView.ID = "EmployeesGrid"
employeesView.AutoGenerateColumns = False
employeesView.DataSourceID = "EmployeeSource"
' Dynamically create field columns to display the desired
' fields from the data source.
' Create an ImageField object to display an employee's photo.
Dim photoImageField As ImageField = New ImageField()
photoImageField.DataImageUrlField = "PhotoPath"
photoImageField.AlternateText = "Employee Photo"
photoImageField.NullDisplayText = "No image on file."
photoImageField.HeaderText = "Photo"
photoImageField.ReadOnly = True
' Create a BoundField object to display an employee's last name.
Dim lastNameBoundField As BoundField = New BoundField()
lastNameBoundField.DataField = "LastName"
lastNameBoundField.HeaderText = "Last Name"
' Create a BoundField object to display an employee's first name.
Dim firstNameBoundField As BoundField = New BoundField()
firstNameBoundField.DataField = "FirstName"
firstNameBoundField.HeaderText = "First Name"
' Add the field columns to the Fields collection of the
' GridView control.
employeesView.Columns.Add(photoImageField)
employeesView.Columns.Add(lastNameBoundField)
employeesView.Columns.Add(firstNameBoundField)
' Add the GridView control to the Controls collection
' of the PlaceHolder control.
GridViewPlaceHolder.Controls.Add(employeesView)
End If
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>ImageField Constructor Example</title>
</head>
<body>
<form id="form1" runat="server">
<h3>ImageField Constructor Example</h3>
<asp:placeholder id="GridViewPlaceHolder"
runat="server"/>
<!-- This example uses Microsoft SQL Server and connects -->
<!-- to the Northwind sample database. Use an ASP.NET -->
<!-- expression to retrieve the connection string value -->
<!-- from the Web.config file. -->
<asp:sqldatasource id="EmployeeSource"
selectcommand="Select [EmployeeID], [LastName], [FirstName], [PhotoPath] From [Employees]"
connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>"
runat="server"/>
</form>
</body>
</html>
Commenti
Utilizzare questo costruttore per inizializzare una nuova istanza della ImageField classe . Questo costruttore viene comunemente usato quando si aggiungono campi a un controllo associato a dati creato in modo dinamico.
Per aggiungere dinamicamente un ImageField oggetto a un controllo associato a dati, creare un nuovo ImageField oggetto, impostarne le proprietà e quindi aggiungerlo all'insieme di campi del controllo associato a dati. Ad esempio, se si usa il GridView controllo , aggiungere l'oggetto ImageField 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.