Represents a field that is displayed as an image in a data-bound control.
See Also: ImageField Members
Syntax
Remarks
The System.Web.UI.WebControls.ImageField class is used by data-bound controls (such as System.Web.UI.WebControls.GridView and System.Web.UI.WebControls.DetailsView) to display an image for each record displayed. The System.Web.UI.WebControls.ImageField object is displayed differently depending on the data-bound control in which it is used. For example, the System.Web.UI.WebControls.GridView control displays an System.Web.UI.WebControls.ImageField object as a column, while the System.Web.UI.WebControls.DetailsView control displays it as a row.
To display images, you must bind an System.Web.UI.WebControls.ImageField object to a field from a data source that contains the URL of an image. This is accomplished by setting the ImageField.DataImageUrlField property. The URL value can be formatted by using the ImageField.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 ImageField.AlternateText property to specify alternate text that applies to all images.
Use the ImageField.DataAlternateTextField property to bind a field from a data source to the Image.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 ImageField.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 ImageField.NullImageUrl property. Instead of an alternate image, you can display alternate text by setting the ImageField.NullDisplayText property.
By default, all declared fields are displayed in a data-bound control. You can hide an System.Web.UI.WebControls.ImageField object in a data-bound control by setting the DataControlField.Visible property to false.
You can customize the header and footer sections of an System.Web.UI.WebControls.ImageField object. To display a caption in the header or footer section, set the DataControlField.HeaderText or DataControlField.FooterText properties, respectively. To display an image in the header section instead of text, set the DataControlField.HeaderImageUrl property. The header section can be hidden in the System.Web.UI.WebControls.ImageField object by setting the DataControlField.ShowHeader property to false.
Some data-bound controls (such as the System.Web.UI.WebControls.GridView control) can show or hide only the entire header section of the control. These data-bound controls do not support the DataControlField.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 System.Web.UI.WebControls.ImageField 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.
| DataControlField.ControlStyle |
The style settings for the child Web server controls of the System.Web.UI.WebControls.ImageField object. |
| DataControlField.FooterStyle |
The style settings for the footer section of the System.Web.UI.WebControls.ImageField object. |
| DataControlField.HeaderStyle |
The style settings for the header section of the System.Web.UI.WebControls.ImageField object. |
| DataControlField.ItemStyle |
The style settings for the data items in the System.Web.UI.WebControls.ImageField object. |
Requirements
Assembly: System.Web (in System.Web.dll)
Assembly Versions: 2.0.0.0
Since: .NET 2.0