System.Web.UI.WebControls Namespace

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.NET Framework version 2.0

Represents a field that is displayed as an image in a data-bound control.

ImageField Class Members

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Constructors Visibility Constructor Parameters public ImageField ( )   Fields Visibility Name Type public static ThisExpression String   Properties Visibility Name Value Type Accessibility public AlternateText String [ Get , Set ] public ConvertEmptyStringToNull Boolean [ Get , Set ] public DataAlternateTextField String [ Get , Set ] public DataAlternateTextFormatString String [ Get , Set ] public DataImageUrlField String [ Get , Set ] public DataImageUrlFormatString String [ Get , Set ] public NullDisplayText String [ Get , Set ] public NullImageUrl String [ Get , Set ] public ReadOnly Boolean [ Get , Set ]   Methods Visibility Name Parameters Return Type protected CopyProperties ( DataControlField newField ) Void protected CreateField ( ) DataControlField public ExtractValuesFromCell ( IOrderedDictionary dictionary , DataControlFieldCell cell , DataControlRowState rowState , Boolean includeReadOnly ) Void protected FormatImageUrlValue ( Object dataValue ) String protected GetDesignTimeValue ( ) String protected GetFormattedAlternateText ( Control controlContainer ) String protected GetValue ( Control controlContainer , String fieldName , PropertyDescriptor& cachedDescriptor ) Object public Initialize ( Boolean enableSorting , Control control ) Boolean public InitializeCell ( DataControlFieldCell cell , DataControlCellType cellType , DataControlRowState rowState , Int32 rowIndex ) Void protected InitializeDataCell ( DataControlFieldCell cell , DataControlRowState rowState ) Void protected OnDataBindField ( Object sender , EventArgs e ) Void public ValidateSupportsCallback ( ) Void

The ImageField class is used by data-bound controls ( such as GridView and DetailsView ) to display an image for each record displayed. The ImageField object is displayed differently depending on the data-bound control in which it is used. For example, the GridView control displays an ImageField object as a column, while the DetailsView control displays it as a row.

To display images, you must bind an ImageField 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 a null reference ( Nothing in Visual Basic ), an image cannot be displayed. You can display an alternate image for a null reference ( Nothing in Visual Basic ) 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 ImageField object in a data-bound control by setting the Visible property to false.

You can customize the header and footer sections of an ImageField 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 ImageField object by setting the ShowHeader property to false.

NOTE: 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 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.

Style property	Description
ControlStyle	The style settings for the child Web server controls of the ImageField object.
FooterStyle	The style settings for the footer section of the ImageField object.
HeaderStyle	The style settings for the header section of the ImageField object.
ItemStyle	The style settings for the data items in the ImageField object.

The following examples illustrate using an ImageField in different scenarios.

GridView ImageField Example Run Sample | View Source

DetailsView with Default Paging Run Sample | View Source

DetailsView PagerSettings, PagerStyle Example Run Sample | View Source

BoundField   ButtonField   CheckBoxField   CommandField   HyperLinkField   TemplateField

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