C# TextBox允許多行 並去除換行符號

        private void Form1_Load(object sender, EventArgs e)
        {
            textBox1.Text = "可以輸入多行";
        }

        private void button1_Click(object sender, EventArgs e)
        {
            textBox1.Multiline = true;//允許多行屬性
            
            //置換換行符號為空白，讓messagebox秀出輸入的字串
            String a = textBox1.Text;
            a = a.Replace("\r\n", "");
            a = a.Replace("\n", "");
            a = a.Replace("\r", "");
            MessageBox.Show(a);
        }