How can I limit the type of characters to enter in a textbox

Google Search is always a good place to start. I used: winform textbox specific characters - Google Search[^] and the first found was this solution: Only allow specific characters in textbox [solved] - StackOverflow[^]

UPDATE

To simplify the proposed solution in the link above, here is a simplified version of the accepted answer in the link provided. Only allows numerics, lower and upper case characters, and selected special characters. All other characters are ignored.

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        textBox1.KeyPress += OnKeyPress;
    }

    private void OnKeyPress(object? sender, KeyPressEventArgs e)
    {
        // allow numerics
        if (e.KeyChar >= '0' && e.KeyChar <= '9')
            return;

        // allow lowercase characters
        if (e.KeyChar >= 'a' && e.KeyChar <= 'z')
            return;

        // allow uppercase characters
        if (e.KeyChar >= 'A' && e.KeyChar <= 'Z')
            return;

        // allow backspace and other special characters in the string
        if ("\b".Contains(e.KeyChar))
            return;

        e.Handled = true;
    }
}

Here is a more compact version using Pattern Matching[^]:

private void OnKeyPress(object? sender, KeyPressEventArgs e)
{
    e.Handled = e.KeyChar switch
    {
        >= '0' and <= '9' => false, // allow numerics
        >= 'a' and <= 'z' => false, // allow lowercase characters
        >= 'A' and <= 'Z' => false, // allow uppercase characters
        '\b' => false,              // allow backspace
        _ => true
    };
}