Figure 1 - These objects will determine if all our data is valid or not. Clear() 'Clear Text Box Name Valid = False 'Boolean = False Else Name Valid = True 'Everything Fine End If End Sub Easy one to start with. Focus() 'Set Focus To Text Box End If End Sub Private Sub txt Email_Lost Focus(sender As Object, e As System. Lost Focus Validate Email() 'Check Email Validity End Sub The expression may look horrible to the layman's eye, but look closer. To check if the user has entered an email that actually exists, you will have to find a different way such as to send a of some sorts.
Based on each of these variables' values, we will know if the data is correct or not. The Leave event fires when the control loses focus. As you can see, Regular Expressions are a vital tool to have at your disposal, so become good friends with them.
Finally, you'll validate all the data when user submitting the form.
You can validate at the time a user is writting by listening to the events of onkeyup and onkeydown.
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.
Well, sometimes a good structured and thought out If statement can suffice, but it can become quite long and cumbersome in the future. By using Regular Expressions this way, you can reduce the chances of getting errors at erratic times. This sub checks the email's format and if it thinks that it matches, it returns True and vice versa.
Also, the more tests you are performing, the slower your app might become. For more information regarding Regular Expressions, you are welcome to look at these two MSDN articles: Because it is always easy to learn by doing things practically, you will be creating an app that makes use of Regular Expressions to determine valid input. NET application and design the form to resemble Figure 1. Obviously this only works for the formatting of the email.
I'm trying to validate the correct format for a phone number in a text box: (000) 000-0000 For a test, i made it so that a messagebox shows up saying "correct" if the format is correct. BUT when the format IS NOT correct, I keep getting an error saying that the index was out of the array. -------\ Public Class Form1 Private Sub Button1_Click(By Val sender As System. '//------- Pre-requisites: 1 Button, 1 Text Box named "phonenumbertxtbox". Substring(8, 1) = "-" Then '// check if length is greater than 8 and if 9th char. Msg Box("Correct") Else : Msg Box("Incorrect") End If Else : Msg Box("Incorrect") End If Else : Msg Box("Incorrect") End If End If End With End Sub Private Sub phonenumbertxtbox_Key Press(By Val sender As Object, By Val e As System. 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: ###-###-####.