Listing 1 PoweredBoundField class declaration

using System;
using System.ComponentModel;
using System.Web.UI.WebControls;
namespace Powered01Cs
{
    public class PoweredBoundField : BoundField
    {

    }
}


Imports System.Web.UI.WebControls

Public Class PoweredBoundField
    Inherits BoundField

End Class

Listing 2 Some PoweredBoundField properties

/// <summary>
/// Enable/Disable Required Validation.
/// </summary>
[
Description("Required Validation"),
Category("Behavior"),
DefaultValue("false"),
]
public bool Required
{
 get
 {
  object o = ViewState["EnableRequired"];
  return (o != null ? (bool)o : false);
 }
 set
 {
  ViewState["EnableRequired"] = value;
 }
}

/// <summary>
/// Required Validation Error Message.
/// </summary>
[
Description("Required Validation Error Message"),
Category("Behavior"),
DefaultValue(""),
]
public string RequiredErrorMessage
{
 get
 {
  object o = ViewState["RequiredErrorMessage"];
  return (o != null ? o.ToString() : "Required Field!!!");
 }
 set
 {
  ViewState["RequiredErrorMessage"] = value;
 }
}
Public Property Required() As Boolean
 Get
  Dim o As Object = ViewState("EnableRequired")
  If (IsNothing(o)) Then
   Return False
  Else
   Return CBool(o)
  End If
 End Get
 Set(ByVal value As Boolean)
  ViewState("EnableRequired") = value
 End Set
End Property

Public Property RequiredErrorMessage() As String
 Get
  Dim o As Object = ViewState("RequiredErrorMessage")
  If (IsNothing(o)) Then
   Return "Required Field!!!"
  Else
   Return CStr(o)
  End If
 End Get
 Set(ByVal value As String)
  ViewState("RequiredErrorMessage") = value
 End Set
End Property

Listing 3 The InitializeCell method where we add the validator controls to the TextBox bound to the DataField

public override void InitializeCell(
    DataControlFieldCell cell, 
    DataControlCellType cellType, 
    DataControlRowState rowState, int rowIndex)
{
 base.InitializeCell(cell, cellType, rowState, rowIndex);
 if (cellType == DataControlCellType.DataCell)
 {
  // If the row is in edit mode try to add Validators
  if ((rowState & DataControlRowState.Edit) != 0 ||
      (rowState & DataControlRowState.Insert) != 0)
  {
   try
   {
    // find the TextBox bound to the DataField
    TextBox tb = (TextBox)cell.Controls[0];
    tb.ID = DataField;
    if (Required)
    {
     // add a RequiredFieldValidator and link it 
     // to the TextBox bound to the DataField
     cell.Controls.Add(GetRequiredValidator(tb.ID,
                       RequiredErrorMessage));
    }
    if (RegularExpressionValidationString != "")
    {
     // add a RegularExpressionValidator and link it 
     // to the TextBox bound to the DataField
     cell.Controls.Add(GetRegularExpressionValidator(
                 tb.ID, RegularExpressionValidationString,
                 RegularExpressionValidationErrorMessage));
    }
   }
   catch { }
  }
 }
}


Public Overrides Sub InitializeCell(
    ByVal cell As DataControlFieldCell, _
    ByVal cellType As DataControlCellType, _
    ByVal rowState As DataControlRowState, _
    ByVal rowIndex As Integer)
 MyBase.InitializeCell(cell, cellType, rowState, rowIndex)
 If cellType = DataControlCellType.DataCell Then
  ' If the row is in edit mode try to add Validators
  If (rowState And DataControlRowState.Edit) <> 0 _
   OrElse (rowState And _
           DataControlRowState.Insert) <> 0 Then
   Try
    ' find the TextBox bound to the DataField
    Dim tb As TextBox = CType(cell.Controls(0), TextBox)
    tb.ID = DataField
    If Required Then
     ' add a RequiredFieldValidator and link it 
     ' to the TextBox bound to the DataField
     cell.Controls.Add(GetRequiredValidator(tb.ID, _
                       RequiredErrorMessage))
    End If
    If RegularExpressionValidationString <> "" Then
     ' add a RegularExpressionValidator and link it 
     ' to the TextBox bound to the DataField
     cell.Controls.Add(GetRegularExpressionValidator( _
      tb.ID, _
      RegularExpressionValidationString, _
      RegularExpressionValidationErrorMessage))
    End If
   Catch ex As Exception
   End Try
  End If
 End If
End Sub

Listing 4 Private functions that build up validator controls

private RegularExpressionValidator 
    GetRegularExpressionValidator(
       string inControlToValidate,
       string inRegExprValidationString, 
       string inRegExprValidationErrorMessage)
{
 RegularExpressionValidator rev = 
       new RegularExpressionValidator();
 rev.ControlToValidate = inControlToValidate;
 rev.ID = String.Concat("RegularExpressionValidatorOf", 
                         inControlToValidate);
 rev.Display = ValidatorDisplay.Dynamic;
 rev.ValidationExpression = inRegExprValidationString;
 rev.ErrorMessage = inRegExprValidationErrorMessage;
 rev.Text = " (!)";
 return rev;
}


Private Function GetRegularExpressionValidator( _
    ByVal inControlToValidate As String, _
    ByVal inRegExprValidationString As String, _
    ByVal inRegExprValidationErrorMessage As String) _ 
    As RegularExpressionValidator
 Dim rev As New RegularExpressionValidator()
 rev.ControlToValidate = inControlToValidate
 rev.ID = "RegularExpressionValidatorOf" & _
           CStr(inControlToValidate)
 rev.Display = ValidatorDisplay.Dynamic
 rev.ValidationExpression = inRegExprValidationString
 rev.ErrorMessage = inRegExprValidationErrorMessage
 rev.Text = " (!)"
 Return rev
End Function


Listing 5 The Default.aspx page used to test PoweredBoundField controls

<%@ Page Language="C#" AutoEventWireup="true"
  CodeFile="Default.aspx.cs" Inherits="_Default" %>
<%@ Register Assembly="Powered01Cs" 
    Namespace="Powered01Cs" 
    TagPrefix="Powered01Cs" %>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
 <title>Adding Validation Capabilities 
        to BoundControls</title>
 <link rel="stylesheet" href="Powered.css" />
</head>
<body>
 <form id="form1" runat="server">
  <h1>Adding Validation Capabilities to BoundControls</h1>
  <fieldset><legend>System Messages</legend>
  <span id="Message" runat="server" style="FONT-SIZE: 8pt; 
  FONT-FAMILY: Verdana, Arial"> </span>
  <asp:ValidationSummary ID="ValidationSummary1"
       Runat="server" />
  </fieldset>
  <p></p>
  <table>
   <tr><td width="50%">
   <asp:GridView ID="GridView1" runat="server" 
    DataSourceID="SqlDataSource1" 
    AutoGenerateColumns="false"
    AutoGenerateEditButton="true" DataKeyNames="VendorId"
    SelectedRowStyle-CssClass="GRDSelectedItem" 
    AlternatingRowStyle-CssClass="GRDAlternatingItem" 
    RowStyle-CssClass="GRDItem" 
    HeaderStyle-CssClass="GRDHeader" 
    BorderColor="black" BorderWidth="1" 
    GridLines="Both" AllowPaging="true" PageSize="20" 
    EnableSortingAndPagingCallbacks="true">
    <Columns>
     <asp:BoundField DataField="VendorId" HeaderText="Id"
          ReadOnly="true" />
     <Powered01Cs:PoweredBoundField 
      RegularExpressionValidationString="^[A-Z]{1,10}\d{4}$" 
      Required="true" 
      RequiredErrorMessage="Must Insert an Account Number" 
      DataField="AccountNumber" 
      HeaderText="Account Number" />
     <Powered01Cs:PoweredBoundField Required="true" 
      RequiredErrorMessage="You Must Insert a Name" 
      DataField="Name" HeaderText="Name" />
    </Columns>
   </asp:GridView>
   <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
    SelectCommand="SELECT VendorId, AccountNumber, Name 
         FROM Purchasing.Vendor" 
    SelectCommandType="Text"
    UpdateCommand="UPDATE Purchasing.Vendor SET 
     AccountNumber=@AccountNumber, Name=@Name WHERE 
     VendorId=@VendorId" UpdateCommandType="Text"
    ConnectionString=
     "<%$ ConnectionStrings:DBConnectionString %>" 
    OldValuesParameterFormatString="{0}" >
   </asp:SqlDataSource>
   </td>
   <td valign="top" align="center" width="50%">
    <img src="Powered01.gif" /></td>
   </tr>
  </table>
 </form>
</body>
</html>