private void buttonEvaluate_Click(object sender, EventArgs e) { try { var val = ExpressionCalculator.Calc(textBoxExpression.Text); MessageBox.Show(string.Format("Value is [{0:f2}]", val), "Success", MessageBoxButtons.OK, MessageBoxIcon.Information); } catch { MessageBox.Show(string.Format("Error parsing [{0}]", textBoxExpression.Text), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } }