Question

On the page load i wanna call a custom validator which validates my page and display corresponding error messages.
How can i do this?

I am using javascript in the custom validator.

Answer 1

You can use Page.IsValid and Page.Validate()

http://weblogs.asp.net/rajbk/archive/2007/03/15/page-isvalid-and-validate.aspx

After Edit: // Here is a working sample:

JS:

<script type="text/javascript">
    function EmpIDClientValidate(ctl, args) {
        // the value is a multiple of 5 if the module by 5 is 0
        args.IsValid = (args.Value % 5 == 0);
    }
</script>

Aspx:

<table>
        <tr>
            <td>
                ID (multiple of 5):
            </td>
            <td>
                <asp:TextBox runat="server" Width="200px" ID="EmpID" Text="12"/>
                <asp:RequiredFieldValidator runat="server" ID="ValidateEmpID" ControlToValidate="EmpID"
                    ErrorMessage="ID is required" Display="dynamic">*
                </asp:RequiredFieldValidator>
                <asp:CustomValidator runat="server" ID="ValidateEmpID2" ControlToValidate="EmpID"
                    ClientValidationFunction="EmpIDClientValidate" ErrorMessage="ID must be a multiple of 5"
                    Display="dynamic" OnServerValidate="ValidateEmpID2_ServerValidate">*
                </asp:CustomValidator>
            </td>
        </tr>
    </table>
    <br />
    <asp:Button runat="server" Text="Submit" ID="Submit" OnClick="Submit_Click" /><br />
    <br />
    <asp:CheckBox runat="server" ID="chkEnableValidators" Checked="True" AutoPostBack="True"
        Text="Validators enabled" OnCheckedChanged="OptionsChanged" />
    <br />
    <asp:CheckBox runat="server" ID="chkEnableClientSide" Checked="True" AutoPostBack="True"
        Text="Client-side validation enabled" OnCheckedChanged="OptionsChanged" />
    <br />
    <asp:CheckBox runat="server" ID="chkShowSummary" Checked="True" AutoPostBack="True"
        Text="Show summary" OnCheckedChanged="OptionsChanged" />
    <br />
    <asp:CheckBox runat="server" ID="chkShowMsgBox" Checked="False" AutoPostBack="True"
        Text="Show message box" OnCheckedChanged="OptionsChanged" />
    <br />
    <br />
    <asp:ValidationSummary runat="server" ID="Summary" DisplayMode="BulletList" HeaderText="<b>Please review the following errors:</b>"
        ShowSummary="true" />
    <asp:Label runat="server" ID="Result" ForeColor="magenta" Font-Bold="true" EnableViewState="False" />

And codebehind:

protected void Page_Load(object sender, EventArgs e)
{
    // To run all validators
    Page.Validate();
    // To run just one validator:
    ValidateEmpID2.Validate();
}

protected void Submit_Click(object sender, EventArgs e)
{
    if (Page.IsValid)
        Result.Text = "Thanks for sending your data";
    else
        Result.Text = "There are some errors, please correct them and re-send the form.";
}

protected void ValidateEmpID2_ServerValidate(object source, ServerValidateEventArgs args)
{
    try
    {
        args.IsValid = (int.Parse(args.Value) % 5 == 0);
    }
    catch
    {
        args.IsValid = false;
    }
}

protected void OptionsChanged(object sender, EventArgs e)
{
    // Examine all the validators on the back.
    foreach (BaseValidator validator in Page.Validators)
    {
        // Turn the validators on or off, depending on the value
        // of the "Validators enabled" check box (chkEnableValidators).
        validator.Enabled = chkEnableValidators.Checked;

        // Turn client-side validation on or off, depending on the value
        // of the "Client-side validation enabled" check box
        // (chkEnableClientSide).
        validator.EnableClientScript = chkEnableClientSide.Checked;
    }

    // Configure the validation summary based on the final two check boxes.
    Summary.ShowMessageBox = chkShowMsgBox.Checked;
    Summary.ShowSummary = chkShowSummary.Checked;
}