Represents a field that is displayed as an image in a data-bound control.
Assembly: System.Web (in System.Web.dll)
The class is used by data-bound controls (such as GridView and DetailsView) to display an image for each record displayed. The object is displayed differently depending on the data-bound control in which it is used. For example, the GridView control displays an object as a column, while the DetailsView control displays it as a row.
To display images, you must bind an object to a field from a data source that contains the URL of an image. This is accomplished by setting the DataImageUrlField property. The URL value can be formatted by using the DataImageUrlFormatString property. Each image can also have alternate text associated with it. This text is displayed when an image cannot be loaded, or is unavailable. Browsers that support the ToolTips feature also display this text as a ToolTip. You can specify the alternate text for a displayed image by using one of the following methods:
Use the AlternateText property to specify alternate text that applies to all images.
Use the DataAlternateTextField property to bind a field from a data source to the AlternateText property of each image. This allows you to have different alternate text for each image displayed. When binding data, you can optionally format the alternate text by using the DataAlternateTextFormatString property.
When the URL value for an image is null, an image cannot be displayed. You can display an alternate image for null field values by setting the NullImageUrl property. Instead of an alternate image, you can display alternate text by setting the NullDisplayText property.
By default, all declared fields are displayed in a data-bound control. You can hide an object in a data-bound control by setting the Visible property to false.
You can customize the header and footer sections of an object. To display a caption in the header or footer section, set the HeaderText or FooterText properties, respectively. To display an image in the header section instead of text, set the HeaderImageUrl property. The header section can be hidden in the object by setting the ShowHeader property to false.
Some data-bound controls (such as the GridView control) can show or hide only the entire header section of the control. These data-bound controls do not support the ShowHeader property for an individual data-bound field. To show or hide the entire header section of a data-bound control, use the control's ShowHeader property (if available).
You also can customize the appearance of the object (font color, background color, and so on) by setting the style properties for the different parts of the field. The following table lists the different style properties.
The style settings for the child Web server controls of the object.
The style settings for the footer section of the object.
The style settings for the header section of the object.
The style settings for the data items in the object.
The following example demonstrates how to use an object in a GridView control to display an image.
<%@ Page language="C#" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> <title>ImageField Example</title> </head> <body> <form id="form1" runat="server"> <h3>ImageField Example</h3> <asp:gridview id="EmployeesGrid" autogeneratecolumns="false" datasourceid="EmployeeSource" runat="server"> <columns> <asp:imagefield dataimageurlfield="PhotoPath" alternatetext="Employee Photo" nulldisplaytext="No image on file." headertext="Photo" readonly="true"/> <asp:boundfield datafield="FirstName" headertext="First Name"/> <asp:boundfield datafield="LastName" headertext="Last Name"/> </columns> </asp:gridview> <!-- 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>
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.