Validating user input in vb net
Each new exception can preserve the information about the previous one by storing it in this property.I have small query , I wanted to fire the validation without closing the form.
I simply need to check the text box to see if the user input is a numeric value, or not (with the exception of a "." and or "/") My code so far, Private Sub Num1_Key Press(By Val sender As System. A name doesn't generally contain weird symbols, and definitely not numbers. This can be from the mouse clicking inside another field, or a Tab key being pressed to navigate to the next input control. ") Else Email Valid = True 'Email is Perfect End If Else 'Not A Match To Pattern Email Valid = False 'Set Boolean Variable To False Message Box. I hope you have learned from this article and that you have enjoyed it as much as I did. That may seem like Captain Obvious speaking, but you'll be amazed at some of the data that gets entered into a name field. I then created an If statement to determine how the input data was formatted and whether or not the data is only alphabetic. Sometimes people are just trying to be funny, or they are literally trying to break your program. If the data is indeed only alphabetic letters (no symbols, no numbers or any other punctuation characters) the test succeeds and stores True inside the Name Valid variable. This is because it becomes more legible than just a normal set of numbers. You could say that a program's testers are supposed to do this; yes, they should - nobody else should. If not, if there is even just one unallowed character that is not supposed to be there, the Match method will return False. Instead of you having to loop through each character to determine what that character is, you simply need the correct Regular Expression pattern. Clear() Surname Valid = False Else Surname Valid = True End If End Sub It is basically the exact same code for the Name box, but I just included the capability to comprehend a space character as well. People expect to enter a phone number in a format similar to this: ###-###-####. In a perfect world, your code would run correctly every time.
You will first see the programming you can use to handle errors, and then you will see how to use validation techniques to prevent bad data from being entered into your application in the first place.
Is Null Or Empty(str Phone Num) Then Phone Valid = re Phone. Text) Then 'Call Phone Validation Function Message Box. I set up my Expression to allow only numbers, but in the format I explained earlier.
Is Match(str Phone Num) 'Check Validity Else Phone Valid = False 'Not Valid / Empty End If Return Phone Valid 'Return True / False End Function Private Sub txt Tel_Lost Focus(sender As Object, e As System. If it isn't valid input, it will clear the textbox and give it the focus again; if it is valid, the Phone Valid variable gets updated to true.
You would never discover this kind of errors at compile time.
Is Null Or White Space(input) Then Return False If Is Numeric(input) Then Return True Dim parts() As String = input. This does assume that you are allowing 1/2/2, .i.e. If not then you also have to check that there is a max of 1 "/" chars in your string. Hook this up to the ' Preview Text Input of the desired textbox Private Sub Set Textbox Numeric Only(sender As Object, e As Text Composition Event Args) Dim regex As New System. The second reason is that you could give to Is Numeric whatever object you want (also a Button for example) and it accepts it.
Working with instances of these classes allows the developer to provide robust error-handling solutions. NET Framework provides two general classes or exceptions that derive from the common An exception associated with the exception whose Inner Exception property you are accessing.