Problem with CheckBox in a datagrid

Discussion in 'ASP .Net' started by mike, Dec 11, 2003.

  1. mike

    mike Guest

    Hi there:

    I've read an excellent "how to"-article by Microsoft (no. 306227) - partly
    cited cited at the end of this email).

    I have implemented the code related to the part "How to Add a CheckBox
    Programmatically" in my code. I have changed it to use a OLDDB.DBReader to
    populate the datagrid and for the databinding. It works perfectly - also
    when using the edit-mode in the datagrid.

    However, the problem is: in "edit-Mode" in the Datagrid using some
    update-coding of mine I cannot read the "value" of the CheckBox which was
    added pogrammatically in case the user changed it. I tried using
    "e.Item.FindControl("CheckBox1")" but it won't work, hoping that the ID of
    the CheckBox was simply CheckBox1 (see code below) . I have also been trying
    to read the value by using e.Item.Cells(whatever).Controls(whatever) but how
    on earth can I now the correct position - that would involve guessing.

    ************my code snippet*********************
    Private Sub DataGrid1_UpdateCommand(ByVal source As Object, ByVal e As
    System.Web.UI.WebControls.DataGridCommandEventArgs) Handles
    DataGrid1.UpdateCommand

    Dim ContactId As Integer, ContactPerson, email, phone, remarks As String
    Dim tb As TextBox, cb As CheckBox, bolValue As Boolean

    ContactId = e.Item.Cells(1).Text

    '****THIS IS THE PART THAT DOES NOT WORK

    cb = CType(e.Item.FindControl("CheckBox1"), CheckBox)
    bolValue = cb.Checked, Boolean

    '****END OF CODE THAT DOES NOT WORK


    tb = CType(e.Item.Cells(4).Controls(0), TextBox)
    ContactPerson = tb.Text
    tb = CType(e.Item.Cells(5).Controls(0), TextBox)
    email = tb.Text
    tb = CType(e.Item.Cells(6).Controls(0), TextBox)
    phone = tb.Text
    tb = CType(e.Item.Cells(7).Controls(0), TextBox)
    remarks = tb.Text

    Dim str1 As String = _
    "UPDATE tblContacts " & _
    "SET ContactPerson='" & ContactPerson & "', ContactPerson_email='" & email &
    "', " & _
    "ContactPerson_phone='" & phone & "', Remarks='" & remarks & "' WHERE
    ContactID=" & ContactId

    RunSQLString(str1)
    DataGrid1.EditItemIndex = -1
    RefreshDataGrid()
    ************end of my code snippet***************

    I still believe that "e.Item.FindControl("CheckBox1")" is the right way to
    go. But how do I know the ID (name) of the CheckBox-control which is added
    by your code ? Is it possible to assign the ID somewhere in your code ?

    I'd appreciate your help and assistance if you do not mind. Thank-you.

    Rgds,
    Mikael

    *******************************************************
    How to Add a CheckBox Programmatically
    The following sample code adds the TemplateColumn and CheckBox controls to
    the grid and binds the data programmatically. First, the sample code adds a
    TemplateColumn control and then adds the check boxes to the Template column.
    Finally, the code adds an event handler to bind the CheckBox control to the
    database.
    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

    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.
    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
    Uncomment the following line of code in the aforementioned code sample:
    'AddHandler oCheckBox.DataBinding, AddressOf BindCheckBox

    This line calls the event handler, Public Sub BindCheckBox, when the
    DataBinding event of the CheckBox control executes. The BindCheckBox
    procedure evaluates the data and properly sets the Checked property of the
    current check box. Notice that the procedure is called for every row in the
    grid as the DataGrid binds each row.
    mike, Dec 11, 2003
    #1
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