When the program loads, it creates an InstalledFontCollection object. It loops over this object's Families collection and adds the names of the fonts to a ListBox.

using System.Drawing.Text;
...
// List the installed fonts.
private void Form1_Load(object sender, EventArgs e)
{
    InstalledFontCollection fonts =
        new InstalledFontCollection();

    foreach (FontFamily font_family in fonts.Families)
    {
        lstFonts.Items.Add(font_family.Name);
    }

    // Select the first font.
    lstFonts.SelectedIndex = 0;
}

The SomethingChanged event handler catches all of the events that influence the font's appearance. This includes:

• The size TextBox's TextChanged event
• The Bold, Italic, Underline, and Strikeout CheckBoxes' CheckedChanged events
• The font ListBox's SelectedIndexChanged event

SomethingChange simply calls the ShowSample function to actually display the sample.

private void SomethingChanged(object sender, EventArgs e)
{
    ShowSample();
}

Function ShowSample builds the necessary FontStyle, parses the font size, and gets the selected font's name. It then builds the font and makes the sample TextBox use it.

// Display a sample of the selected font.
private void ShowSample()
{
    // Compose the font style.
    FontStyle font_style = FontStyle.Regular;
    if (chkBold.Checked) font_style |= FontStyle.Bold;
    if (chkItalic.Checked) font_style |= FontStyle.Italic;
    if (chkUnderline.Checked) font_style |= FontStyle.Underline;
    if (chkStrikeout.Checked) font_style |= FontStyle.Strikeout;

    // Get the font size.
    float font_size = 8;
    try
    {
        font_size = float.Parse(txtSize.Text);
    }
    catch
    {
    }

    // Get the font family name.
    string family_name = "Times New Roman";
    if (!(lstFonts.SelectedItem == null))
        family_name = lstFonts.SelectedItem.ToString();

    // Set the sample's font.
    txtSample.Font = new Font(family_name, font_size, font_style);
}