HOW TO: Use a CheckBox Web Control in a DataGrid in Visual Studio .NET

Requirements

• Microsoft Windows 2000 Professional, Microsoft Windows 2000 Server, Microsoft Windows 2000 Advanced Server, or Microsoft Windows NT 4.0 Server

• The DataGrid control, data retrieval, and data binding on Web forms
• Microsoft Visual Studio .NET
• Microsoft SQL Server

How to Add a CheckBox to a DataGrid Web Control by Using the TemplateColumn Object

1. Create a new ASP .NET Web application.
2. In Server Explorer, create a connection to the SQL Server Pubs database. Drag the Authors table from Server Explorer onto WebForm1 to create SqlConnection1 and SqlDataAdapter1 objects.
3. Right-click the SqlDataAdapter1 object, and then click Generate Data Set.
4. In the Choose a DataSet area, click New. For the name, type DsAuthors.
5. In the Choose which table(s) to add to the DataSet section, select the Authors table.
6. Click to select the Add this DataSet to the designer check box, and then click OK to create the DataSet.
7. Drag a DataGrid control from the toolbox onto WebForm1, and then set the following properties for the grid:

      Property Name           Value
      -----------------------------
   
      DataSource              DsAuthors1
      DataMember              Authors
      DataKeyField            Au_id
   					

8. Add the following code to the Page_Load event to fill the DataSet and to bind the DataGrid to the DataSet:

   SqlDataAdapter1.Fill(DsAuthors1)
   If Not IsPostBack Then
       DataGrid1.DataBind()
   End If
   					

9. Press F5 to compile and to run the program. Notice that the data is displayed in the DataGrid.

How to Add a CheckBox to a DataGrid Web Control by Using the User Interface (UI) and the TemplateColumn Object

1. Select the DataGrid columns you want to be displayed.
   1. Right-click the DataGrid, and then click Property Builder. In the left pane, click Columns to display the Columns properties for the DataGrid.
   2. Click to clear the Create columns automatically at run-time check box.
   3. In the Column List section, in the Selected Columns box, add the au_id and au_lname fields.
   4. Add a Template Column to the Selected Columns box, and change the Header Text to Contract. Click OK to close the Properties Builder.
2. Edit the ColumnTemplate and bind it to the DataSet.
   1. Right-click the DataGrid, and then click Edit Template, Columns[2] - Contract to open the template editor.
      
      The template editor has four sections: HeaderTemplate, ItemTemplate, EditItemTemplate, and FooterTemplate. You will use the ItemTemplate section.
   2. Use the ItemTemplate property to control the appearance of a data item in the TemplateColumn. To do this, create a template that defines how the item is displayed in the column:
      1. Drag a CheckBox control from the toolbox into the ItemTemplate section of the Template Column.
      2. Select the CheckBox control. In the Properties window, locate the DataBindings option. Click the icon to open the DataBindings dialog box.
      3. In the Bindable Properties list, select Checked.
      4. In the Simple Bound section, in the Container, DataItem list, select Contract. Click OK.
         
         The check portion of the CheckBox control will be bound to the Contracts field, but the text portion of the CheckBox control will not be bound and will appear blank.
      5. Right-click Edit Template, and then click End Template Editing to close the TemplateColumn editor and to return to the grid.
      6. Save and test the application. Notice that the Contract column is displayed as a check box, and its properties reflect the data from the Authors table in the SQL Server Pubs database.

How to Add a CheckBox Programmatically

1. Type or paste the following code sample in the Page_Load event. The code creates a TemplateColumn object and sets its header text.

   SqlDataAdapter1.Fill(DsAuthors1)
   
   'Create a new TemplateColumn object.
   Dim tcol As New TemplateColumn()
   With tcol
       .HeaderText = "CheckBox Column"
       ' Call DynamicItemTemplate to add the child controls to the Template 
       ' Column and bind them to the Data source.    
       .ItemTemplate = New DynamicItemTemplate()
   End With
   
   DataGrid1.Columns.Add(tcol)
   If Not IsPostBack Then
        DataGrid1.DataBind()
   End If
   					

2. Type or paste the following code after the Public Class WebForm1, End class.

   Public Class DynamicItemTemplate
       ' ITemplate - When implemented by a class, defines the Control object
       ' to which child controls and templates belong. These child controls 
       ' are in turn defined within an inline template.
       Implements ITemplate
   
       Public Overridable Overloads Sub InstantiateIn(ByVal container As Control) Implements ITemplate.InstantiateIn
           ' InstantiateIn - When implemented by a class, defines the Control 
           ' object to which child controls and templates belong. These child 
           ' controls are, in turn, defined within an inline template.
           ' 
           ' Create an instance of a CheckBox object.
           Dim oCheckBox As CheckBox = New CheckBox()
   
           ' When the DataBinding event of the CheckBox fires, call the sub 
           ' BindCheckBox to properly bind.  
           ' AddHandler oCheckBox.DataBinding, AddressOf BindCheckBox
           'Add the CheckBox to the controls collection.
           container.Controls.Add(oCheckBox)
       End Sub
   
   
       Public Sub BindCheckBox(ByVal sender As Object, ByVal e As EventArgs)
           'Create a new instance of a CheckBox. 
           Dim oCheckBox As CheckBox = CType(sender, CheckBox)
           Dim container As DataGridItem = CType(oCheckBox.NamingContainer, DataGridItem)
           'Evaluate the data from the Grid item and set the Checked property 
           ' appropriatly
           If container.DataItem("contract").GetType.ToString = "System.DBNull" Then
               oCheckBox.Checked = False
           Else
               oCheckBox.Checked = CBool(container.DataItem("contract"))
           End If
   
       End Sub
   End Class
   						

   NOTE: The binding code is commented to make the process easier to understand.
3. Save and run the code. Notice that the Template Column and unbound CheckBox controls were added.

How to Iterate Through the Control to Test the Value of the CheckBox

  'AddHandler oCheckBox.DataBinding, AddressOf BindCheckBox