Telerik UI for ASP.NET AJAX

Column elements

The columns in a GridTableView contain a header, a set of items, and a footer:

Header

The Header (GridHeaderItem) is the cell on the top of each grid column. Header cells always appear for all grid columns unless the ShowHeader property of the grid (or table view) is False. By default, the ShowHeader property for the grid and all its table views is True. The Header remains persistent when the pages of the grid change.

From Q2 2012 on the grid column headers can be grouped together under a multi-column header. You can find more info here: Multicolumn Headers.

You can customize the appearance of the header using the RadGrid property builder or the HeaderStyle section of the RadGrid property pane. From the Q3 2013 Beta release the headers text can be rotated by assigning a rgRotateHeader class as demonstrated below.

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<HeaderStyle CssClass="rgRotateHeader" />

The column header allows the user to perform the following special functions:

  • If the AllowSorting property is True, users can use the header for sorting data based on the column value.

  • If the ShowGroupPanel property is True, users can drag the header to group data based on the column value.

  • If the ClientSettings.AllowColumnsReorder property is True, users can reorder columns by dragging the column header and dropping it in a new location.

  • If the ClientSettings.Resizing.AllowColumnResize property is True, users can resize columns by dragging on the sides of the column header.

Items

Column Items are the regular data cells of the grid. Neighboring items form a single row.

Each column type that displays data has a property which is responsible for formatting the values in the items section of the column, using the formatting rules defined in ASP.NET. For example, if you have a GridBoundColumn with a DataType of "DateTime", setting the DataFormatString property to "{0:d}" causes it to display its value using the short date representation format).

When using a bound column populated with values of type System.Double, the contents with precision above 15 digits are automatically rounded. This can produce erratic behavior, for example when filtering. If this is a problem for your grid, you can use the DataFormatString to increase the precision of the bound column. This is illustrated in the code sample below:

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<telerik:GridBoundColumn DataField="Value" HeaderText="Value" UniqueName="Value"
  SortExpression="Value" DataType="System.Double" DataFormatString="{0:G17}">
</telerik:GridBoundColumn>

The following MSDN articals provide additional information about formatting, format strings, and DateTime formatting:

Footer

The Footer element of a column is similar to the Header element, but it is placed at the bottom of the grid. It cannot provide header-specific functions like reordering, resizing and sorting of columns. Rather, you can set the FooterText property of the column to display information about the column (such as summary information).

If you are using column aggregates, these are automatically displayed in the footer.

To have a Footer row in your grid, set the ShowFooter property to true. Then you can customize the Footer appearance using the RadGrid property builder or FooterStyle section of the RadGrid property pane.

Sorting

RadGrid supports sorting of column item elements. To enable sorting, you must set the AllowSorting property of the grid to True. You can disable the sorting feature for individual columns by setting their AllowSorting property to False.

Sorting is controlled by sorting expressions on the GridTableView object. You can specify the SortExpressions property collection declaratively to provide an initial sort order or manipulate the sorting expressions at runtime to alter the sort order of columns.

Grouping

RadGrid can group its items based on the value of the items in a column. In addition to (or instead of) letting users group data using GridGroupPanel, you can group the data in the grid by setting the GroupByExpressions property of a table view in the grid. You can set the group-by expressions declaratively at design time, or programatically in the code-behind.

Filtering

RadGrid natively supports filtering of table columns for its master and detail tables. To enable or disable filtering, set the AllowFilteringByColumn property of the RadGrid or GridTableView control.

When filtering is enabled, each column displays an independent filter menu that allows filtering over all records in the table view. You can disable filtering for individual grid columns by setting their AllowFiltering property to False.

The available filtering expressions depend on the DataType property for each column. This property is set automatically based on the data source for each column.

For more information about filtering, see Basic filtering.

Aggregates

RadGrid can calculate aggregated values based on the values in the grid items. Use the Aggregate property of the column to specify the function that should be used to aggregate the column values. The aggregated value is displayed in the footer of the column when you set the ShowFooter property to True.

For more information about column aggregates, see Column Aggregates.

Client-side Operations

Some of the operations related to grid columns are performed client-side (without postback to the server). This can significantly optimize the grid performance. Client-side operations include Resizing columns and Reordering columns operations.

Note

If you are enabling reordering and resizing functionality in the grid, the ShowHeader property must be True.

Visibility and rendering of columns

The Display, Visible, and ReadOnly properties of a column let you control its visibility and rendering, as described below:

  • Display concerns only the client-side appearance the column in browser mode. When Display is False, the column is rendered in the browser, but all the cells are styled with display: none. The Display property does not affect the appearance of the column editor in an edit form, but if the grid uses in-place editors, the column editor will not appear.

  • Visible determines whether the column's cells are rendered in browser mode. When Visible is False, the column is not visible in browser mode because it is not rendered at all. The visible property does not affect the appearance of the column editor in an edit form, but if the grid uses in-place editors, the column editor will not appear.

  • ReadOnly concerns whether the column editor is visible in edit mode. This property is only available for column types that allow editing. The ReadOnly property has no effect on whether the column appears in browser mode.

Note

None of these properties can prevent you from accessing the column cells' contents server-side using the UniqueName of the column.

Columns in Edit Mode

When the grid is in edit mode, users can edit the data in the columns in one of two ways:

  • If the table view's EditMode property is "InPlace", the ;content of all cells in editable columns (columns that represent editable data that do not have ReadOnly set to True), changes into a column editor. For example, a cell in GridBoundColumn becomes a text box so that users can edit the text. For more information about in-place editing, see In place.

  • If the table view's Edit Mode is not "InPlace", the content of the cells remains the same, but an edit form that contains the column editors appears. For information about edit forms, see Edit forms.

Adding Columns Programmatically

You can programmatically add columns in the code-behind by adding column objects to the Columns property collection of GridTableView.

Caution

When creating columns programatically, use the Columns property of the GridTableView, NOT its RenderColumns or AutoGeneratedColumns property. Adding columns to one of the latter two collections will not affect the appearance of the grid.

When adding columns programmatically, you must add the created columns to the Columns collection at a different point, depending on whether you are instantiating the column on PageInit or PageLoad.

When adding columns using on PageInit, you must add the columns to the Columns collection after their properties have been set:

When adding columns on PageLoad (when IsPostBack is False), the columns should be added to the Columns collection before setting their properties:

For more information about creating columns dynamically, see Programmatic creation.Creating a RadGrid Programmatically

Note

The Columns properties of the RadGrid control and of the grids MasterTableView are equivalent. Accessing or modifying either of these collections has the same effect as accessing or modifying the other.

Customizing columns programmatically

You can change the properties of columns that are added at design time. How you do this depends on whether the columns are auto-generated, or added declaratively.

Auto-generated columns

You can customize the properties of auto-generated columns at runtime by providing a handler for the grid's ColumnCreated event. In the event handler, cast the column to the appropriate type and set its attributes. The following example shows this technique used to set the ReadOnly and DataFormatString properties for a column with a UniqueName of "BirthDate" which has DateTime DataType:

Note

Note that by default the header text of the auto generated columns is the name of the data field split by capital letters. To control this behavior you can use the EnableSplitHeaderText property. Its default value is true. If you set it to false, the header text will be the same as the name of the data field.

Declarative columns

To change the settings for declarative columns at runtime, write a handler for the PreRender event of the grid, traverse the Columns collection to locate the column of interest, and alter its properties. You must then rebind the grid by calling its Rebind() method to reflect the changes:

For more information about the auto-generated and declarative columns collections, see Getting familiar with server-side API.

See Also