Adding text to text box when event ''MouseHover'' is active

Question

I'm new at C#. I want to add '#' to HALLO (in the textBox) each time when you hover your mouse over the button.

This is what i have:

public partial class Form1 : Form
{
    string Q = "HALLO";
    string hashtag = "#";

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        tB1.Text = Q;
    }

    private void bT1_MouseHover(object sender, EventArgs e)
    {
        tB1.Text += hashtag;

        if (Q.Length > 20)
        {
            tB1.Clear();
        }

        lBkarakters.Text = Convert.ToString(tB1.Text.Length);
    }

    }
    }

It does add the '#', but HALLO is gone.

Answer 1

public partial class Form1 : Form
{
    string Q = "HALLO";
    string hashtag = "#";

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        tB1.Text = Q;
    }

    private void bT1_MouseHover(object sender, EventArgs e)
    {
        tB1.Text += hashtag;
    }
}

or

public partial class Form1 : Form
{
    string Q = "HALLO";
    string hashtag = "#";

    public Form1()
    {
        InitializeComponent();

        tB1.Text = Q;
    }

    private void bT1_MouseHover(object sender, EventArgs e)
    {
        tB1.Text += hashtag;
    }
}

Make sure you're event is registered: