Validating a Registration Form Using C#

Validating a Registration Form Using Regular Expression in C#

Today, I will teach you how to validate a Registration Form using  Regular Expressions in C#. Regular Expression contains the formated rules and check lengths to validate the inputs of a certain texbox. This method is very useful because it will help you restrict each fields in the form.

Let’s get started:

Open Microsoft Visual Studio 2008 and create new Windows Form Application for C#. Then, do the following design of a Form as follows.

Go to the Solution Explorer, click the “View Code”  to make the code editor appear.

In the code editor, import the regural expression library above the namespace.

using System.Text.RegularExpressions;

After that, create the following method inside the class. These methods are use to format the specific fields using the correct patern.

 //Method for validating email address
 private static Regex Email_Address()
 {
 string Email_Pattern = @"^(?!\.)(""([^""\r\\]|\\[""\r\\])*""|"
 + @"([-a-z0-9!#$%&'*+/=?^_`{|}~]|(?<!\.)\.)*)(?<!\.)"
 + @"@[a-z0-9][\w\.-]*[a-z0-9]\.[a-z][a-z\.]*[a-z]$";

 return new Regex(Email_Pattern, RegexOptions.IgnoreCase);
 }
 //Method for string only validation
 private static Regex StringOnly()
 {
 string StringAndNumber_Pattern = "^[a-zA-Z]";

 return new Regex(StringAndNumber_Pattern, RegexOptions.IgnoreCase);
 }
 //Method for numbers only validation
 private static Regex NumbersOnly()
 {
 string StringAndNumber_Pattern = "^[0-9]*$";

 return new Regex(StringAndNumber_Pattern, RegexOptions.IgnoreCase);
 }
 //Method for validating password
 private static Regex ValidPassword()
 {
 string Password_Pattern = "(?!^[0-9]*$)(?!^[a-zA-Z]*$)^([a-zA-Z0-9]{8,15})$";

 return new Regex(Password_Pattern, RegexOptions.IgnoreCase);
 }

Go back to the design view, double click the button and do the following code for the validation of the registration form.

//it validate all textboxes when the button clicked
 private void button1_Click(object sender, EventArgs e)
 {
 //for firstname 
 if (Valid_Fname.IsMatch(txtfName.Text) != true)
 {
 MessageBox.Show("Firstname accepts only alphabetical characters", "Invalid", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
 txtfName.Focus();
 return;
 }
 //for Lastname 
 if (Valid_Lname.IsMatch(txtLname.Text) != true)
 {
 MessageBox.Show("Lastname accepts only alphabetical characters", "Invalid", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
 txtLname.Focus();
 return;
 }
 //for Address 
 if (txtAdd.Text == "")
 {
 MessageBox.Show("Address cannot be empty!", "Invalid", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
 txtAdd.Focus();
 return;
 }
 //for Contacts 
 if (Valid_Contact.IsMatch(txtContact.Text) != true)
 {
 MessageBox.Show("Contact accept numbers only.", "Invalid", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
 txtContact.Focus();
 return;
 }
 //for username 
 if (txtuname.Text == "")
 {
 MessageBox.Show("Username cannot be empty!", "Invalid", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
 txtuname.Focus();
 return;
 }
 //for password 
 if (Valid_Password.IsMatch(txtPass.Text) != true)
 {
 MessageBox.Show("Password must be atleast 8 to 15 characters. It contains atleast one Upper case and numbers.", "Invalid", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
 txtPass.Focus();
 return;
 }
 //for Email Address 
 if (Valid_Email.IsMatch(txtEmail.Text) != true)
 {
 MessageBox.Show("Invalid Email Address!","Invalid",MessageBoxButtons.OK ,MessageBoxIcon.Exclamation );
 txtEmail.Focus(); 
 return; 
 }

 //success message
 MessageBox.Show("You are now successfully registered.");

 //hidding all object in the form
 foreach(Control txt in this.Controls)
 {
 if (txt is Control)
 {
 txt.Visible = false;
 
 }
 }
 }

Output:

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