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The C# Column
Grooming the DataGrid control
 Programmers
are never satisfied with what is shipped with a development environment.
They always require something more than what is available to create
an application using that environment. For example, instead of normal
menus, we may want menus to appear sliding. Instead of the blue
coloured menu selection bar, we may want to change it to suit the
current skin of the application window. In short, developers try
to customise the available controls to suit their requirements.
If you are thinking of customising the DataGrid control to give
it a different look then this article will prove helpful to you.
In this article we will change the background and foreground color of the currently
selected row in the DataGrid control. We will also rearrange the sequence of
the columns before displaying the data in the table.
Create a WinForm application and place the DataGrid control on it. Open the
Server Explorer window. Go to the table, which you want to provide as data source.
Drag and drop the table on the DataGrid control. If it requires a password to
access the data source, a message box will be popped up to ask you whether you
want the password to get displayed in source code or not. Say yes to it otherwise
the connection string will lack the password and a connection to the data source
will not get established. The following references will get added as data members
of the Form1 class.
private.SqlCommand sqlSelectCommand1;
private SqlCommand sqlInsertCommand1;
private SqlConnection sqlConnection1;
private SqlDataAdapter sqlDataAdapter1;
The command string for SELECT and INSERT statements as well as the connection
string also get created.
Now right-click on the SqlDataAdapter1 component and select ‘Generate DataSet’
from the pop-up menu. The ‘Generate DataSet’ dialog box appears. Change
the DataSet name to ds1 and click ‘OK’. This adds a DataSet reference
to the component tray.
 Add the
Load event handler and write the following statement in it.
sqlDataAdapter1.Fill ( ds1 ) ;
The InitializeComponent( ) method contains the code to connect to the data source.
Check whether the connection string is constructed properly and then run the
program. You will see the datagrid control filled with data as shown in the
following figure.
The control in our form shows records of the ‘bank’ database. For
the field having datatype bit (or boolean) DataGrid control displays a checkbox.
Records having value 1 (or true) in that field appear checked.
Let us now start the customisation work. Firstly, we will arrange the order
in which columns should appear. By default DataGrid shows the columns in order
specified in the SQL query. If we want to change this order we can change the
query.
However, what if the order of columns is dependent on an action taken by the
user? This can be managed by using the DataGridTableStyle class. Don’t
confuse this class with the table (datasource) displayed in the DataGrid control.
The DataGridTableStyle class represents the grid drawn in the control.
Therefore, to customise the appearance of the grid for a DataTable, we can use
the DataGridTableStyle class. To associate the name of the table with a table
style the MappingName property of the DataGridTableStyle class is initialised
with the table name i.e. the name of the data source. Name of our table happens
to be ‘account’.
The DataGrid class has a property called TableStyles. It returns a reference
to the object of the GridTableStylesCollection class. An object of the GridTableStylesCollection
class holds a collection of the objects of DataGridTableStyle class. Each object
can specify different table styles.
The DataGridTableStyle class has a property called GridColumnStyles. It returns
a reference to an object of the GridColumnStylesCollection class. This collection
holds objects of the DataGridColumnStyle class. We can customise the appearance
of a column through the DataGridColumnStyle class. To associate a column style
with a column in the data table, we must initialise the MappingName property
of the DataGridColumnStyle class with the column name.
We cannot instantiate the DataGridColumnStyle class because it is an abstract
class. Instead we use the derived classes DataGridTextBoxColumn or the DataGridBoolColumn.
The DataGridBoolColumn makes the column look and behave like a check box. This
class is useful when we have a field of type bool in the data source.
We will now write the code to customise the columns, add the column styles in
the columns style collection maintained in the table style object, and then
add the table style to the datagrid control. This code is to be written in the
Load event handler.
DataGridTableStyle ts = new DataGridTableStyle( ) ;
ts.MappingName = “account” ;
DataGridBoolColumn bcol = new DataGridBoolColumn( ) ;
bcol.MappingName = “ATM” ;
bcol.Width = 30 ;
bcol.AllowNull = false ;
ts.GridColumnStyles.Add ( bcol ) ;
DataGridTextBoxColumn column = new DataGridTextBoxColumn( ) ;
column.MappingName = “accno” ;
column.HeaderText = “Account No.” ;
column.Width = 80 ;
ts.GridColumnStyles.Add ( column ) ;
column = new DataGridTextBoxColumn( ) ;
column.MappingName = “name” ;
column.HeaderText = “Name” ;
column.Width = 110 ;
ts.GridColumnStyles.Add ( column ) ;
column = new DataGridTextBoxColumn( ) ;
column.MappingName = “bal” ;
column.HeaderText = “Balance” ;
column.Width = 110 ;
ts.GridColumnStyles.Add ( column ) ;
dataGrid1.TableStyles.Add ( ts ) ;
We have changed the order of columns as ATM, accno, name and bal. Here, we have
used the properties like HeaderText and Width to change the column heading and
width of the columns respectively. The Add( ) method is used to add the column
and table style to the respective collections. Now run the program. You will
see the columns arranged in the order set in the table style.
Next week we will customise the background and foreground
color of the selected row.
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Yashavant Kanetkar, one of
the first Express Computer columnists, is an established software
expert, speaker and author with several best-sellers to his
credit, including titles like “Let Us C” and the “Fundas” series.
Contact him at kanetkar@dcubesoft.com |
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