A closer look at Windows Forms (Part 2) – Visual Basic/C#

byAlexandre

If you haven’t looked at Part 1, here is the link!

This tutorial will go in a bit more details about Windows Forms, more precisely, we will look at how to retrieve and store user data from a Form. To do so, we will be using the following controls:

TextBox
RichTextBox
ComboBox
Button

As you start using more and more controls, you will begin to see similarities between them. Just drag and drop the control you wish to add from the Toolbox onto the form. It should look like the form below.

Modify the controls as follow:
1. Rename all you controls with relevant names, like btnAddUser for the button.
2. Change the DropDownStyle property of the ComboBox control to DropDownList.
3. Add male and female in the gender ComboBox Item property. This property works like a list, it means that each line represent one item.

What we will want to do next is, when the Button is pressed, grab all the data from the form and put it in memory. For that, we can create an object corresponding to the content of the form.

In other words, the object will contain the form fields. Here is how I implemented the Client object.

Visual Basic

Public Class Client
    Public Property FullName As String
    Public Property Gender As String
    Public Property Address As String
    Public Property Details As String

    Public Sub New(FullName As String,
                   Gender As String,
                   Address As String,
                   Details As String)
        Me.FullName = FullName
        Me.Gender = Gender
        Me.Address = Address
        Me.Details = Details
    End Sub
End Class

namespace FormsControls
{
    class Client
    {
        public string FullName { get; set; }
        public string Gender { get; set; }
        public string Address { get; set; }
        public string Details { get; set; }

        public Client(string FullName,
                      string Gender,
                      string Address,
                      string Details)
        {
            this.FullName   = FullName;
            this.Gender     = Gender;
            this.Address    = Address;
            this.Details    = Details;
        }
    }
}

Here is what my form looks like, feel free to recreate it to your taste!

Don’t forget that you should rename at least the controls that you plan on using in your code. This should simplify your coding task a lot.

An example for a TextBox name could be: tbFirstName, tbLastName, and so on.

You can modify some other properties on the form like the maximum text length of the Text Boxes, but I am done with the interface and will go straight in the code. The first thing we will want to do is to validate our user input. Always remember that our user is “kind” of our enemy here because we don’t know what he/she has in mind (remember that this goes both ways) and we don’t want wrong values entered.

There are multiple techniques and variation to validation, but I will only validate one thing for now: the fields must all be filled. Double click on the button to create a new (default) click event.

Visual Basic

Public Class frmClients
    Private Sub btnAddUser_Click(sender As Object, e As EventArgs) Handles btnAddUser.Click
        If txtFullName.Text = String.Empty Or
           txtAddress.Text = String.Empty Or
           cbGender.Text = String.Empty Or
           rtbDetails.Text = String.Empty Then
            MessageBox.Show("")
            Return
        End If

        'Standard process goes here
    End Sub
End Class

        private void btnAddUser_Click(object sender, EventArgs e)
        {
            if (txtFullName.Text == String.Empty ||
                txtAddress.Text == String.Empty ||
                cbGender.Text == String.Empty ||
                rtbDetails.Text == String.Empty)
            {
                MessageBox.Show("All fields must be filled.");
                return;
            }

            //Standard process goes here
        }

Note: remember that if you copy and paste that code, you might have to enter the event name manually in the Events section of the property window.

I am simply validating that if any of the fields Text value is equal to an empty string, the user will be warned with a message box and the method will stop to give a chance to our user correct the data entered.

In the same method, we will write the standard method of creating a new client, fill the object with the user data and display the created client to our user.

Visual Basic

Public Class frmClients
    Private Sub btnAddUser_Click(sender As Object, e As EventArgs) Handles btnAddUser.Click
        If txtFullName.Text = String.Empty Or
           txtAddress.Text = String.Empty Or
           cbGender.Text = String.Empty Or
           rtbDetails.Text = String.Empty Then
            MessageBox.Show("")
            Return
        End If

        Dim FullName As String
        Dim Address As String
        Dim Gender As String
        Dim Details As String

        FullName = txtFullName.Text
        Address = txtAddress.Text
        Gender = cbGender.Text
        Details = rtbDetails.Text

        Dim NewClient As New Client(FullName,
                                    Gender,
                                    Address,
                                    Details)
    End Sub
End Class

    public partial class frmUsers : Form
    {
        public frmUsers()
        {
            InitializeComponent();
        }

        private void btnAddUser_Click(object sender, EventArgs e)
        {
            if (txtFullName.Text == String.Empty ||
                txtAddress.Text == String.Empty ||
                cbGender.Text == String.Empty ||
                rtbDetails.Text == String.Empty)
            {
                MessageBox.Show("All fields must be filled.");
                return;
            }

            //Standard process goes here
            string FullName     = txtFullName.Text;
            string Address      = txtAddress.Text;
            string Gender       = cbGender.Text;
            string Details      = rtbDetails.Text;

            Client NewClient = new Client(FullName, Address, Gender, Details);

            MessageBox.Show(NewClient.ToString());
        }
    }

I just want to point out that I am using variables to store the content of the TextBoxes before assigning them to the new object, this is my working standard. In other words you could have input the fields Text property directly into the object constructor. What I mean is something like:

' Visual Basic Dim NewClient As Client = New Client(txtFirstName.Text, txtLastName.Text, cbGender.Text, rtbDetails.Text)

// C# Client NewClient = new Client(txtFirstName.Text, txtLastName.Text, cbGender.Text, rtbDetails.Text);

On the final line I am using the ToString() method to display the object in the MessageBox but this displays only the namespace because it is the default ToString() method that comes from the parent. That’s why we have to override this method in the class to make sure it displays relevant information.

Visual Basic

Public Class Client
    Public Property FullName As String
    Public Property Gender As String
    Public Property Address As String
    Public Property Details As String

    Public Sub New(FullName As String,
                   Gender As String,
                   Address As String,
                   Details As String)
        Me.FullName = FullName
        Me.Gender = Gender
        Me.Address = Address
        Me.Details = Details
    End Sub

    Public Overrides Function ToString() As String
        Dim OutputString As String
        OutputString = String.Format("Client added \nFull name: {0} \nGender: {1} \nAddress: {2} \nDetails: {3}", FullName, Gender, Address, Details)

        Return OutputString
    End Function
End Class

namespace FormsControls
{
    class Client
    {
        public string FullName { get; set; }
        public string Gender { get; set; }
        public string Address { get; set; }
        public string Details { get; set; }

        public Client(string FullName,
                      string Gender,
                      string Address,
                      string Details)
        {
            this.FullName   = FullName;
            this.Gender     = Gender;
            this.Address    = Address;
            this.Details    = Details;
        }

        public override string ToString()
        {
            string OutputString = String.Empty;
            OutputString = String.Format("Client added \nFull name: {0} \nGender: {1} \nAddress: {2} \nDetails: {3}", FullName, Gender, Address, Details);

            return OutputString;
        }
    }
}

Pay close attention to how the ToString method is created (using override). That directive specifies that it overrides an already existing method from its parent (object). It might be useful to specify that the ‘\n’ is what will return to a new line in the MessageBox we will display.

You can now give this program a test and try to enter no value in one of the fields to see what happens. Again, breakpoints can be used to really see what the computer is doing at every steps.