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3.17. Format the DataGridView
Formatting the .NET 1.x
DataGrid ranges from awkward to nearly impossible.
However, thanks to its multi-layered model, formatting the
DataGridView is far easier. This model builds on a
single class, the DataGridViewCellStyle, which
encapsulates key formatting properties. You can assign different
DataGridViewCellStyle objects to separate rows,
columns, or even distinct cells.
Note: By using a few simple style properties, you can configure
the appearance of the entire grid, individual columns, or rows with
important data.
3.17.1. How do I do that?
The DataGridView already looks better than the
DataGrid in its default state. For example,
you''ll notice that the column headers have a modern,
flat look and become highlighted when the user moves the mouse over
them. However, there''s much more you can do with the
help of the DataGridViewCellStyle class.
The DataGridViewCellStyle collects all the
formatting properties of the DataGridView. It
defines appearance-related settings (e.g., color, font), and data
formatting (e.g., currency, date formats). All in all, the
DataGridViewCellStyle provides the following key
properties:
Alignment
Sets how text is justified inside the
cell.
BackColor and ForeColor
Set the color of the
cell background and the color of the cell text.
Font
Sets the font used for the cell text.
Format
A format string that configures how
numeric or date data values will be formatted as strings. You can use
the standard .NET format specifiers and your own custom format
strings. For example, C designates a currency
value. (For more information, look up the index entry
"numeric format strings" in the
MSDN help.)
NullText
A string of text that will be substituted
for any null (missing) values.
SelectionBackColor and SelectionForeColor
Set the cell
background colors and text colors for selected cells.
WrapMode
Determines if text will flow over multiple
lines (if the row is high enough to accommodate it) or if it will be
truncated. By default, cells will wrap.
The interesting part is that you can create and set
DataGridViewCellStyle objects at different levels.
When the DataGridView displays a cell, it looks
for style information in several places. Here''s the
order from highest to lowest importance:
DataGridViewCell.Style
DataGridViewRow.DefaultCellStyle
DataGridView.AlternatingRowsDefaultCellStyle
DataGridView.RowsDefaultCellStyle
DataGridViewColumn.DefaultCellStyle
DataGridView.DefaultCellStyle
In other words, if DataGridView finds a
DataGridViewCellStyle object assigned to the
current cell (option 1), it always uses it. If not, it checks the
DataGridViewCellStyle for the row, and so on.
The following code snippet performs column-specific formatting. It
ensures that all the values in the CustomerID column are given a
different font, alignment, and set of colors. Figure 3-13 shows the result.
Note: If you use the design-time data-binding features of Visual
Studio, you can avoid writing this code altogether. Just click the
Edit Columns link in the Properties Window and use the designer to
choose the formatting.
Dim Style As DataGridViewCellStyle = _
DataGridView1.Columns("CustomerID").DefaultCellStyle
Style.Font = New Font(DataGridView1.Font, FontStyle.Bold)
Style.Alignment = DataGridViewContentAlignment.MiddleRight
Style.BackColor = Color.LightYellow
Style.ForeColor = Color.DarkRed
Figure 3-13. A DataGridView with a formatted column
3.17.2. What about...
...the easiest way to apply custom cell formatting? Sometimes, you
want to call attention to cells with certain values. You could handle
this task by iterating over the entire grid, looking for those cells
that interest you. However, you can save time by responding to the
DataGridView.CellFormatting
event. This event occurs as the grid is being filled. It gives you
the chance to inspect the cell and change its style before it
appears.
Here''s an example that formats a cell to highlight
high prices:
Private Sub DataGridView1_CellFormatting(ByVal sender As System.Object, _
ByVal e As System.Windows.Forms.DataGridViewCellFormattingEventArgs) _
Handles DataGridView1.CellFormatting
'' Check if this is the right column.
If DataGridView1.Columns(e.ColumnIndex).Name = "Price" Then
'' Check if this is the right value.
If e.Value > 100 Then
e.CellStyle.ForeColor = Color.Red
e.CellStyle.BackColor = Color.Yellow
End If
End If
End Sub
Keep in mind that you should reuse style objects if at all possible.
If you assign a new style object to each cell,
you''ll consume a vast amount of memory. A better
approach is to create one style object, and assign it to multiple
cells that use the same formatting.
