Validating numeric input
Most current web browsers support this attribute and will communicate missing required input to the user, using standard web browser dialog mechanisms.These dialogs are expected to respect the settings and preferences of the user in the web browser (and operating system), such as default font-size, colors, and language.In the example below, the attribute is added to the input field.If your web browser supports HTML5, it will not allow you to submit the form without entering text into the input field.If the email address is not in the standard format (containing "@" and "."), the validation fails, an Error Provider icon is displayed, and the event is canceled. Active Control property to the current form, focus events occur in the following order: Caution Do not attempt to set focus from within the Enter, Got Focus, Leave, Lost Focus, Validating, or Validated event handlers.This example requires that a Text Box and Error Provider control have been created on a form. Index Of("@")) Then error Message = "" Return True End If End If error Message = "Email address must be valid email address format." Control Chars. Validating Dim error Msg As String If Not Valid Email Address(text Box1. Doing so can cause your application or the operating system to stop responding.private: void text Box1_Validating( Object^ sender, System:: Component Model:: Cancel Event Args^ e ) void text Box1_Validated( Object^ sender, System:: Event Args^ e ) public: bool Valid Email Address( String^ email Address, [Out]interior_ptrprivate void text Box1_Validating(object sender, System. Cancel Event Args e) private void text Box1_Validated(object sender, System. Length = 0 Then error Message = "Email address is required." Return False End If ' Confirm that there is an "@" and a "." in the email address, and in the correct order. Cr _ "For example '[email protected]' " Return False End Function Private Sub text Box1_Validating(By Val sender As Object, _ By Val e As System. Text, error Msg) Then ' Cancel the event and select the text to be corrected by the user. Event Args e) public bool Valid Email Address(string email Address, out string error Message) Private Function Valid Email Address(By Val email Address As String, By Ref error Message As String) As Boolean ' Confirm there is text in the control.
Client-side validation alone does not ensure security; therefore data needs to be validated on the server-side as well.Depending on browser support, the url field can be automatically validated when submitted.Some smartphones recognize the url type, and adds ".com" to the keyboard to match url input.Some smartphones recognize the email type, and add ".com" to the keyboard to match email input.You will learn more about input restrictions in the next chapter.