private void btnNewOPeration_Click(object sender, EventArgs e)
{
            int Number1 = 0;
            int Number2 = 0;
            Random rndNumber = new Random();

            // If the user clicked the Level 1 button,
            // the operation will be performed on numbers from 1 to 9
            if (rdoLevel1.Checked == true)
            {
                Number1 = rndNumber.Next(1, 10);
                Number2 = rndNumber.Next(1, 10);
            }
            else if (rdoLevel2.Checked == true)
            {
                // If the user clicked the Level 2 button,
                // the operation will be performed on numbers from 10 to 19
                Number1 = rndNumber.Next(10, 30);
                Number2 = rndNumber.Next(10, 30);
            }
            else if (rdoLevel3.Checked == true)
            {
                // If the user clicked the Level 3 button,
                // the operation will be performed on numbers from 21 to 49
                Number1 = rndNumber.Next(30, 50);
                Number2 = rndNumber.Next(30, 50);
            }
            else if (rdoLevel4.Checked == true)
            {
                // If the user clicked the Level 4 button,
                // the operation will be performed on numbers from 51 to 99
                Number1 = rndNumber.Next(50, 101);
                Number2 = rndNumber.Next(50, 101);
            }

            // Display the numbers to the user
            lblOperand1.Text = Number1.ToString();
            lblOperand2.Text = Number2.ToString();

            // Just in case, empty the Result text box
            txtResult.Text = "";
            // Give focus to the Result text box
            txtResult.Focus();
}

private void rdoLevel1_Click(object sender, EventArgs e)
{
            btnNewOPeration_Click(sender, e);
}

private void rdoAddition_Click(object sender, EventArgs e)
{
            lblOperation.Text = "+";
}

private void rdoSubtraction_Click(object sender, EventArgs e)
{
            lblOperation.Text = "-";
}

private void rdoMultiplication_Click(object sender, EventArgs e)
{
            lblOperation.Text = "*";
}

private void rdoDivision_Click(object sender, EventArgs e)
{
            lblOperation.Text = "/";
}

private void btnCheckResult_Click(object sender, EventArgs e)
{
    double Number1, Number2;
    double UserResult, OurResult;
    Random RandomNumber = new Random();

    // It is hard to perform a comparison on a division
    // So we will have to do some gymastic here to get something
    // We will use this variable to format the number 
    // to appear as 0.00
    // That will allow us to perform the comparision
    // on a decimal number with a precision of 2
    string strFixedResult;
    strFixedResult = "";

    string[] Congratulations = new string[]{ 
            "Right :) - WOW - Good Answer!",
            "Good Answer :) - You are Impressive", 
            "Right Answer :) - What a Good Job!", 
            "Good :) - You Are Greaaaaaaaaaaaat", 
            "Wonderful Answer :) - You Know It" 
            };
    string[] WrongAnswers = { 
            "Uhhhhhhhhhh - Bad Answer", 
            "Wrong - You will do better next time", 
            "Nop", 
            "Common - You can do Better Than That!",
            "No - You are probably getting tired" 
            };

    // Make sure the user provides a result
    if (txtResult.Text == "")
    {
        MessageBox.Show("You must provide a result before clicking the button");
        return;
    }

    // Use exception handling to get the result
    UserResult = double.Parse(txtResult.Text);

    Number1 = double.Parse(lblOperand1.Text);
    Number2 = double.Parse(lblOperand2.Text);

    // Get the user's answer
    if (rdoAddition.Checked == true)
    {
        OurResult = Number1 + Number2;
        // Format the result to appear with 2 decimal numbers
        strFixedResult = string.Format("{0:F}", Number1 + Number2);
    }

    if (rdoSubtraction.Checked == true)
    {
        OurResult = Number1 - Number2;
        strFixedResult = string.Format("{0:F}", Number1 - Number2);
    }

    if (rdoMultiplication.Checked == true)
    {
        OurResult = Number1 * Number2;
        strFixedResult = string.Format("{0:F}", Number1 * Number2);
    }

    if (rdoDivision.Checked == true)
    {
        OurResult = Number1 / Number2;
        strFixedResult = string.Format("{0:F}", Number1 / Number2);
    }

    // Check if the user's answer is the right one
    // Because of the division, we will format the result as 0.00
    // then perform the comparison
    if (strFixedResult == double.Parse(txtResult.Text).ToString("F"))
        MessageBox.Show(Congratulations[RandomNumber.Next(0, 4)],
                        "Elementary Operations",
                        MessageBoxButtons.OK, MessageBoxIcon.Question);
    else
    {
        MessageBox.Show(WrongAnswers[RandomNumber.Next(0, 4)],
                        "Elementary Operations",
                        MessageBoxButtons.OK, MessageBoxIcon.Information);
    }

    // After checking the user's answer, generate a new operation
    btnNewOPeration_Click(sender, e);
}