User Input Validation - Client & Server

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User Input Validation - Client & Server - in VB.NET

This tutorial shows how you can validate the input of users using ASP.NET and VB This tutorial shows how the ASP.NET tools make it easy for you to validate user input, both client-side and server-side.

First we add the form elements from the Toolbox, including the RequiredFieldValidator, RegularExpressionValidator and the ValidationSummary.

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Note the CustomValidator control, which allows us to create a custom rule for validation. This particular one checks to see if a date is in the correct format:

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="textEmail" Display="Dynamic" ErrorMessage="Email Address is Required" ValidationGroup="AllValidators">*</asp:RequiredFieldValidator>
Email:
<asp:TextBox ID="textEmail" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ControlToValidate="textEmail" Display="Dynamic" ErrorMessage="Email Address must be in the format abc@xyz.abc" ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*" ValidationGroup="AllValidators">Invalid Format</asp:RegularExpressionValidator><br />

<asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="textNumberInParty" ErrorMessage="Number in Party is Required" ValidationGroup="AllValidators">*</asp:RequiredFieldValidator>
Number in Party:
<asp:TextBox ID="textNumberInParty" runat="server" Width="45px"></asp:TextBox>
<asp:RangeValidator ID="RangeValidator1" runat="server" ControlToValidate="textNumberInParty" Display="Dynamic" ErrorMessage="Please enter 1-20 for the number of people in your party" MaximumValue="20" MinimumValue="1" Type="Integer" ValidationGroup="AllValidators">Enter a number between 1 and 20</asp:RangeValidator><br />

<asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server" ControlToValidate="textPreferredDate" Display="Dynamic" ErrorMessage="Date is Required" ValidationGroup="AllValidators">*</asp:RequiredFieldValidator>
Preferred Date:
<asp:TextBox ID="textPreferredDate" runat="server"></asp:TextBox>
<asp:CustomValidator ID="CustomValidator1" runat="server" ControlToValidate="textPreferredDate" Display="Dynamic" ErrorMessage="Format: m/d/yyyy" OnServerValidate="CustomValidator1_ServerValidate" ValidationGroup="AllValidators" ClientValidationFunction="validateDate">Invalid format (m/d/yyyy)</asp:CustomValidator><br />

<asp:RequiredFieldValidator ID="validatorRequiredPhoneNumber" runat="server" ControlToValidate="textPhoneNumber" Display="Dynamic" ErrorMessage="You must provide a phone number">*</asp:RequiredFieldValidator>
<asp:CheckBox ID="checkPhoneConfirmation" runat="server" AutoPostBack="True" OnCheckedChanged="checkPhoneConfirmation_CheckedChanged" Text="Confirm Reservation by Phone" /><br />
Tel. No.
<asp:TextBox ID="textPhoneNumber" runat="server" Enabled="False"></asp:TextBox>
<asp:RegularExpressionValidator ID="validatorRegExPhoneNumber" runat="server" ControlToValidate="textPhoneNumber" Display="Dynamic" ErrorMessage="Phone number format is invalid" ValidationExpression="((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}">Invalid Format</asp:RegularExpressionValidator><br />
<asp:Button ID="buttonSubmit" runat="server" OnClick="buttonSubmit_Click" Text="Submit" ValidationGroup="AllValidators" /><br />
<asp:Label ID="labelResponse" runat="server"></asp:Label><br />
<asp:ValidationSummary ID="ValidationSummary1" runat="server" ValidationGroup="AllValidators" />

</div>
</form>

In the code-behind file we have the following:

Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

labelResponse.Text = ""

End Sub
Protected Sub buttonSubmit_Click(ByVal sender As Object, ByVal e As EventArgs)

If Page.IsValid Then

labelResponse.Text = "Your request has been processed. Thank you."

Else

labelResponse.Text = "Date is not valid."

End If

End Sub
Protected Sub CustomValidator1_ServerValidate(ByVal source As Object, ByVal args As ServerValidateEventArgs)

Try

DateTime.ParseExact(args.Value, "d", Nothing)
args.IsValid = True

Catch

args.IsValid = False

End Try

End Sub
Protected Sub checkPhoneConfirmation_CheckedChanged(ByVal sender As Object, ByVal e As EventArgs)

If checkPhoneConfirmation.Checked Then

textPhoneNumber.Enabled = True
validatorRequiredPhoneNumber.ValidationGroup = "AllValidators"
validatorRegExPhoneNumber.ValidationGroup = "AllValidators"

Else

textPhoneNumber.Enabled = False
validatorRequiredPhoneNumber.ValidationGroup = ""
validatorRegExPhoneNumber.ValidationGroup = ""

End If

End Sub

For client-side validation of the date field, we can use a bit of JavaScript:

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Note: For this to work, the 'EnableClientScript' Property of the CustomValidator has to be set to True.

var iDay, iMonth, iYear;
var arrValues;
arrValues = args.Value.split("/");
iMonth = arrValues[0];
iDay = arrValues[1];
iYear = arrValues[2];

var testDate = new Date(iYear, iMonth - 1, iDay);
if ((testDate.getDate() != iDay) ||

(testDate.getMonth() != iMonth - 1) ||
(testDate.getFullYear() != iYear))

{

args.IsValid = false;
return;

}

return true;

} </script>

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