![]() ![]() Start Visual Studio and create a Desktop VB.NET application and design the form to resemble Figure 1. 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.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. They make use of a pattern matching system to match the input with a certain pattern of data. Regular Expressions are extremely powerful. So what can we do? The answer is simple: Use Regular Expressions! That is what they were invented for. Also, the more tests you are performing, the slower your app might become. Well, sometimes a good structured and thought out If statement can suffice, but it can become quite long and cumbersome in the future. There are some more tests, but I want to keep this article straightforward and basic enough. For example : If you are only supposed to type in 50 characters, you must not be able to enter more than fifty. Range test – This tests checks to see if entered values are within a specified range.For example: If a user is supposed to enter a name, numbers and some special symbols must not be allowed. Permitted Character test – This test ensure that no illegal characters are entered.For example: Integers of dates that do not need conversion afterwards. Type test – This test checks if the input is the correct type.Format test – This test determines if the entered string is in the correct format.Determining whether or not data is valid can sometimes be a painstaking process as there are numerous tests that need to be thought of. In simple terms, validation refers to ensuring entered data is well, valid. Today you will learn how to use regular Expressions to validate user input. This is why I decided to make use of Regular Expressions here within this article. Because everyone has a different way of doing things, my methods might not be 100% the same as your methods. Any resemblance to other material is an un-intentional coincidence and should not be misconstrued as malicious, slanderous, or any anything else hereof.Validating user input can be quite a pain, especially if you do not know what techniques and what namespaces are at your disposal. This article is entirely original, unless specified. This article should not be construed as the best practices white paper. NOTE: This article is purely for demonstration. errorProvider1.SetError(dateTimePicker1, "" ).errorProvider1.SetError(dateTimePicker1, "Appointment cannot be scheduled in the weekend. Please select a weekday" ).errorProvider1.SetError(textBox2, "Please enter your age as a number" ).errorProvider1.SetError(textBox2, "You must be atleast 18 years old to setup a test" ).errorProvider1.SetError(textBox2, "" ).errorProvider1.SetError(textBox2, "Please enter your Age" ).errorProvider1.SetError(textBox1, "" ).errorProvider1.SetError(textBox1, "Please enter your Name" ).MessageBox.Show( "Please enter valid data" ).MessageBox.Show( "Appointment will be created now" ).if (bValidName & bValidAge & bValidTestDate).bool bValidTestDate = ValidateTestDate().private void button1_Click( object sender, System.EventArgs e).private void dateTimePicker1_Validating( object sender, e).private void textBox2_Validating( object sender, e).private void textBox1_Validating( object sender, e).errorProvider1.ContainerControl = this.private void Form1_Load( object sender, System.EventArgs e).private void label1_Click( object sender, System.EventArgs e).button1.Click += new System.EventHandler( this. ![]() label4.Text = "Setup Driving Test Appointment" dateTimePicker1.Validating += new ( this. dateTimePicker1.Name = "dateTimePicker1" label1.Click += new System.EventHandler( this. ![]()
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