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Today you will learn how to use regular Expressions to validate user input. In simple terms, validation refers to ensuring entered data is well, valid. Type test – This test checks if the input is the correct type.įormat test – This test determines if the entered string is in the correct format.ĭetermining whether or not data is valid can sometimes be a painstaking process as there are numerous tests that need to be thought of.For example: Integers of dates that do not need conversion afterwards.Permitted Character test – This test ensure that no illegal characters are entered.For example: If a user is supposed to enter a name, numbers and some special symbols must not be allowed.Range test – This tests checks to see if entered values are within a specified range.For example : If you are only supposed to type in 50 characters, you must not be able to enter more than fifty. There are some more tests, but I want to keep this article straightforward and basic enough. Well, sometimes a good structured and thought out If statement can suffice, but it can become quite long and cumbersome in the future. Also, the more tests you are performing, the slower your app might become. So what can we do? The answer is simple: Use Regular Expressions! That is what they were invented for. Regular Expressions are extremely powerful. They make use of a pattern matching system to match the input with a certain pattern of data. By using Regular Expressions this way, you can reduce the chances of getting errors at erratic times.įor more information regarding Regular Expressions, you are welcome to look at these two MSDN articles: This means that as a programmer, you have the power to supply the exact pattern for the input you desire in any text input field.Regular Expression Language – Quick Reference.īecause 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.
Start Visual Studio and create a Desktop VB.NET application and design the form to resemble Figure 1.
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