Custom validation on text boxes

Question

I have a table with about 30 textboxes. Each row has 2 textboxes that have the same prefix but different suffix such as txtAvg From and txtAvg To. I need to loop through the table and perform custom validation on the textboxes:

1. only integers
2. if both to and from textboxes are filled in I have to check that the value in from textbox is smaller than the from value.
3. range entered in each textbox is 1-100

I might need more validations later on. Also, if the to textbox is filled in then the from isn't required and vice versa. No textbox is required.

I need to do server side validation. Should I add custom validation control? If yes, then for each textbox? Do I set controltovalidate? I need to display the correct error next to each row when submit button is clicked. And obviously if page is not valid then don't do anything further.

I don't want to add different validation controls. Only a custom validator. I also need to do it dynamically and when the user clicks the submit button I want validation to occur and show (*) next to the row with the error and show the complete error message in validation summary.

I tried to add the control but it doesn't get fired when button is clicked.

Private Sub AddCustomValidation(ByVal container As Control)
    Dim custom As CustomValidator

    Dim vldtxt As TextBox

    For Each ctrl In container.Controls
        If TypeOf ctrl Is TextBox Then
            vldtxt = CType(ctrl, TextBox)
            custom = New CustomValidator
            custom.Text = "To field must be bigger than from field"
            custom.ControlToValidate = vldtxt.ID
            AddHandler custom.ServerValidate, AddressOf CustomValidation

            '  custom.ServerValidate += New System.Web.UI.WebControls.ServerValidateEventHandler(customvalidation)

            Me.form1.Controls.Add(custom)
        Else
            AddCustomValidation(ctrl)
        End If
    Next
End Sub

Protected Sub CustomValidation(ByVal source As System.Object, ByVal args As System.Web.UI.WebControls.ServerValidateEventArgs)

    Dim vldtxt As TextBox
    Dim othertxt As TextBox
    Dim othertxtid As String
    Dim txtid As String
    Dim lower As String
    Dim higher As String

    For Each ctrl As Control In tbl1.Controls
        vldtxt = TryCast(ctrl, TextBox)
        othertxt = TryCast(ctrl, TextBox)

        If vldtxt IsNot Nothing Then

            txtid = ctrl.ID
            ''check if to is not empty and if not empty then check that that to value is higher
            ''than from value
            If ((txtid.ToLower.EndsWith("to")) And (vldtxt.Text <> "")) Then

                higher = (vldtxt.Text)
                othertxtid = vldtxt.ID.Replace("To", "From")
                othertxt = Page.FindControl(othertxtid)
                othertxt.ID = othertxtid
                lower = (othertxt.Text)
                If lower = String.Empty Or higher = String.Empty Then
                    args.IsValid = True
                End If

                If Int32.Parse(lower) >= Int32.Parse(higher) Then
                    args.IsValid = False
                End If
            Else
                args.IsValid = True
            End If



        End If
    Next
End Sub

The layout is something like this:

<table id="tbl1" runat="server" cellpadding="0" cellspacing="3">
    <tr>
        <td>From price</td>
        <td>
            <asp:TextBox runat="server" ID="txtPriceFrom">
        </td>
        <td>To price</td>
        <td>
            <asp:TextBox runat="server" ID="txtPriceTo">
        </td>
        <td>From yield</td>
        <td>
            <asp:TextBox runat="server" ID="txtYieldFrom">
        </td>
        <td>To yield</td>
        <td>
            <asp:TextBox runat="server" ID="txtYieldTo">
        </td>
    </tr>
</table>

Answer 1

You can use ASP.NET Validation Controls:

1. RegularExpressionValidator

2. CustomValidator (validate in code behind)

3. RangeValidator

   <asp:CustomValidator ID="CustomValidator1" runat="server" 
       ErrorMessage="if both to and from textboxes are filled in I have to check that the value in from textbox is smaller than the from value" >
   </asp:CustomValidator>
   
   <table>
       <tr>
           <td>From price</td>
           <td>
               <asp:TextBox runat="server" ID="txtPriceFrom"></asp:TextBox>
   
               <asp:RegularExpressionValidator runat="server" 
                   ControlToValidate="txtPriceFrom"
                   ErrorMessage="Please Enter Only Numbers" 
                   ForeColor="Red" 
                   ValidationExpression="^\d+$">
               </asp:RegularExpressionValidator>
   
               <asp:RangeValidator runat="server" 
                   ControlToValidate="txtPriceFrom"
                   ErrorMessage="Range entered in each textbox is 1-100"
                   MaximumValue="100" MinimumValue="1">
               </asp:RangeValidator>
           </td>
           <td>To price</td>
           <td>
               <asp:TextBox runat="server" ID="txtPriceTo"></asp:TextBox>
               ...
           </td>
           <td>From yield</td>
           <td>
               <asp:TextBox runat="server" ID="txtYieldFrom"></asp:TextBox>
               ...
           </td>
           <td>To yield</td>
           <td>
               <asp:TextBox runat="server" ID="txtYieldTo"></asp:TextBox>
               ...
           </td>
       </tr>
   </table>