C# halt until button is pressed

Question

I'm building a calculator in c#. I want to halt the calculator with error sound until clear button is pressed. Like while calculating square root, the no. is -ve.

Here's the part of calculating square root

 private void buttonSquareRoot_Click(object sender, EventArgs e)
    {
        num1 = double.Parse(textBox1.Text);
        if (num1 < 0.0)
        {
            textBox1.Text = "Invalid Input";
        }
        else
        {
            result = Math.Sqrt(double.Parse(textBox1.Text));
            textBox1.Text = Convert.ToString(result);
        }
    }

After error message i want program to halt until clear button is clicked. i have already made clear button which goes like this.

 private void buttonClear_Click(object sender, EventArgs e)
    {
        textBox1.Text = "";
    }

Answer 1

You can disable all buttons you need until you need them again.

void SetControlsAbility(bool isEnabled)
{
    // for every control you need:
    yourControl.Enabled = isEnabled;
}

Then

private void buttonSquareRoot_Click(object sender, EventArgs e)
{
    num1 = double.Parse(textBox1.Text);
    if (num1 < 0.0)
    {
        textBox1.Text = "Invalid Input";
        SetControlsAbility(false);
    }
    else
    {
        result = Math.Sqrt(double.Parse(textBox1.Text));
        textBox1.Text = Convert.ToString(result);
    }
}

And

private void buttonClear_Click(object sender, EventArgs e)
{
    textBox1.Text = "";
    SetControlsAbility(true);
}

Answer 2

private void buttonSquareRoot_Click(object sender, EventArgs e)
    {
        num1 = double.Parse(textBox1.Text);
        if (num1 < 0.0)
        {
            textBox1.Text = "Invalid Input";
            **buttonSquareRoot.Enabled = False;**
        }
        else
        {
            result = Math.Sqrt(double.Parse(textBox1.Text));
            textBox1.Text = Convert.ToString(result);
        }
    }


private void buttonClear_Click(object sender, EventArgs e)
    {
        textBox1.Text = "";
        buttonSquareRoot.Enabled = True;
    }