Sizing Options in the Windows Forms DataGridView Control

Artigo
04/23/2007

DataGridView rows, columns, and headers can change size as a result of many different occurrences. The following table shows these occurrences.

Occurrence	Description
User resize	Users can make size adjustments by dragging or double-clicking row, column, or header dividers.
Control resize	In column fill mode, column widths change when the control width changes; for example, when the control is docked to its parent form and the user resizes the form.
Cell value change	In content-based automatic sizing modes, sizes change to fit new display values.
Method call	Programmatic content-based resizing lets you make opportunistic size adjustments based on cell values at the time of the method call.
Property setting	You can also set specific height and width values.

By default, user resizing is enabled, automatic sizing is disabled, and cell values that are wider than their columns are clipped.

The following table shows scenarios that you can use to adjust the default behavior or to use specific sizing options to achieve particular effects.

Scenario	Implementation
Use column fill mode for displaying similarly sized data in a relatively small number of columns that occupy the entire width of the control without displaying the horizontal scroll bar.	Set the AutoSizeColumnsMode property to Fill.
Use column fill mode with display values of varying sizes.	Set the AutoSizeColumnsMode property to Fill. Initialize relative column widths by setting the column FillWeight properties or by calling the control AutoResizeColumns method after filling the control with data.
Use column fill mode with values of varying importance.	Set the AutoSizeColumnsMode property to Fill. Set large MinimumWidth values for columns that must always display some of their data or use a sizing option other than fill mode for specific columns.
Use column fill mode to avoid displaying the control background.	Set the AutoSizeMode property of the last column to Fill and use other sizing options for the other columns. If the other columns use too much of the available space, set the MinimumWidth property of the last column.
Display a fixed-width column, such as an icon or ID column.	Set AutoSizeMode to None and Resizable to False for the column. Initialize its width by setting the Width property or by calling the control AutoResizeColumn method after filling the control with data.
Adjust sizes automatically whenever cell contents change to avoid clipping and to optimize the use of space.	Set an automatic sizing property to a value that represents a content-based sizing mode. To avoid a performance penalty when working with large amounts of data, use a sizing mode that calculates displayed rows only.
Adjust sizes to fit values in displayed rows to avoid performance penalties when working with many rows.	Use the appropriate sizing-mode enumeration values with automatic or programmatic resizing. To adjust sizes to fit values in newly displayed rows while scrolling, call a resizing method in a Scroll event handler. To customize user double-click resizing so that only values in displayed rows determine the new sizes, call a resizing method in a RowDividerDoubleClick or ColumnDividerDoubleClick event handler.
Adjust sizes to fit cell contents only at specific times to avoid performance penalties or to enable user resizing.	Call a content-based resizing method in an event handler. For example, use the DataBindingComplete event to initialize sizes after binding, and handle the CellValidated or CellValueChanged event to adjust sizes to compensate for user edits or changes in a bound data source.
Adjust row heights for multiline cell contents.	Ensure that column widths are appropriate for displaying paragraphs of text and use automatic or programmatic content-based row sizing to adjust the heights. Also ensure that cells with multiline content are displayed using a WrapMode cell style value of True. Typically, you will use an automatic column sizing mode to maintain column widths or set them to specific widths before row heights are adjusted.

Resizing with the Mouse

By default, users can resize rows, columns, and headers that do not use an automatic sizing mode based on cell values. To prevent users from resizing with other modes, such as column fill mode, set one or more of the following DataGridView properties:

You can also prevent users from resizing individual rows or columns by setting their Resizable properties. By default, the Resizable property value is based on the AllowUserToResizeColumns property value for columns and the AllowUserToResizeRows property value for rows. If you explicitly set Resizable to True or False, however, the specified value overrides the control value is for that row or column. Set Resizable to NotSet to restore the inheritance.

Because NotSet restores the value inheritance, the Resizable property will never return a NotSet value unless the row or column has not been added to a DataGridView control. If you need to determine whether the Resizable property value of a row or column is inherited, examine its State property. If the State value includes the ResizableSet flag, the Resizable property value is not inherited.

Automatic Sizing

There are two kinds of automatic sizing in the DataGridView control: column fill mode and content-based automatic sizing.

Column fill mode causes the visible columns in the control to fill the width of the control's display area. For more information about this mode, see Column Fill Mode in the Windows Forms DataGridView Control.

You can also configure rows, columns, and headers to automatically adjust their sizes to fit their cell contents. In this case, size adjustment occurs whenever cell contents change.

Note
If you maintain cell values in a custom data cache using virtual mode, automatic sizing occurs when the user edits a cell value but does not occur when you alter a cached value outside of a CellValuePushed event handler. In this case, call the UpdateCellValue method to force the control to update the cell display and apply the current automatic sizing modes.

If content-based automatic sizing is enabled for one dimension only—that is, for rows but not columns, or for columns but not rows—and WrapMode is also enabled, size adjustment also occurs whenever the other dimension changes. For example, if rows but not columns are configured for automatic sizing and WrapMode is enabled, users can drag column dividers to change the width of a column and row heights will automatically adjust so that cell contents are still fully displayed.

If you configure both rows and columns for content-based automatic sizing and WrapMode is enabled, the DataGridView control will adjust sizes whenever cell contents changed and will use an ideal cell height-to-width ratio when calculating new sizes.

To configure the sizing mode for headers and rows and for columns that do not override the control value, set one or more of the following DataGridView properties:

ColumnHeadersHeightSizeMode
RowHeadersWidthSizeMode
AutoSizeColumnsMode
AutoSizeRowsMode

To override the control's column sizing mode for an individual column, set its AutoSizeMode property to a value other than NotSet. The sizing mode for a column is actually determined by its InheritedAutoSizeMode property. The value of this property is based on the column's AutoSizeMode property value unless that value is NotSet, in which case the control's AutoSizeColumnsMode value is inherited.

Use content-based automatic resizing with caution when working with large amounts of data. To avoid performance penalties, use the automatic sizing modes that calculate sizes based only on the displayed rows rather than analyzing every row in the control. For maximum performance, use programmatic resizing instead so that you can resize at specific times, such as immediately after new data is loaded.

Content-based automatic sizing modes do not affect rows, columns, or headers that you have hidden by setting the row or column Visible property or the control RowHeadersVisible or ColumnHeadersVisible properties to false. For example, if a column is hidden after it is automatically sized to fit a large cell value, the hidden column will not change its size if the row containing the large cell value is deleted. Automatic sizing does not occur when visibility changes, so changing the column Visible property back to true will not force it to recalculate its size based on its current contents.

Programmatic content-based resizing affects rows, columns, and headers regardless of their visibility.

Programmatic Resizing

When automatic sizing is disabled, you can programmatically set the exact width or height of rows, columns, or headers through the following properties:

System.Windows.Forms.DataGridView.RowHeadersWidth
System.Windows.Forms.DataGridView.ColumnHeadersHeight
System.Windows.Forms.DataGridViewRow.Height
System.Windows.Forms.DataGridViewColumn.Width

You can also programmatically resize rows, columns, and headers to fit their contents using the following methods:

These methods will resize rows, columns, or headers once rather than configuring them for continuous resizing. The new sizes are automatically calculated to display all cell contents without clipping. When you programmatically resize columns that have InheritedAutoSizeMode property values of Fill, however, the calculated content-based widths are used to proportionally adjust the column FillWeight property values, and the actually column widths are then calculated according to these new proportions so that all columns fill the available display area of the control.

Programmatic resizing is useful to avoid performance penalties with continuous resizing. It is also useful to provide initial sizes for user-resizable rows, columns, and headers, and for column fill mode.

You will typically call the programmatic resizing methods at specific times. For example, you might programmatically resize all columns immediately after loading data, or you might programmatically resize a specific row after a particular cell value has been modified.

Customizing Content-based Sizing Behavior

You can customize sizing behaviors when working with derived DataGridView cell, row, and column types by overriding the System.Windows.Forms.DataGridViewCell.GetPreferredSize(System.Drawing.Graphics,System.Windows.Forms.DataGridViewCellStyle,System.Int32,System.Drawing.Size), System.Windows.Forms.DataGridViewRow.GetPreferredHeight(System.Int32,System.Windows.Forms.DataGridViewAutoSizeRowMode,System.Boolean), or System.Windows.Forms.DataGridViewColumn.GetPreferredWidth(System.Windows.Forms.DataGridViewAutoSizeColumnMode,System.Boolean) methods or by calling protected resizing method overloads in a derived DataGridView control. The protected resizing method overloads are designed to work in pairs to achieve an ideal cell height-to-width ratio, avoiding overly wide or tall cells. For example, if you call the AutoResizeRows(DataGridViewAutoSizeRowsMode,Boolean) overload of the AutoResizeRows method and pass in a value of false for the Boolean parameter, the overload will calculate the ideal heights and widths for cells in the row, but it will adjust the row heights only. You must then call the AutoResizeColumns method to adjust the column widths to the calculated ideal.

Content-based Sizing Options

The enumerations used by sizing properties and methods have similar values for content-based sizing. With these values, you can limit which cells are used to calculate the preferred sizes. For all sizing enumerations, values with names that refer to displayed cells limit their calculations to cells in displayed rows. Excluding rows is useful to avoid a performance penalty when you are working with a large quantity of rows. You can also restrict calculations to cell values in header or nonheader cells.

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Sizing Options in the Windows Forms DataGridView Control

Resizing with the Mouse

Automatic Sizing

Programmatic Resizing

Customizing Content-based Sizing Behavior

Content-based Sizing Options

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