C#数学运算表达式解释器

C#数学运算表达式解释器

测试文件内容：

a=2+3*2;
b=2*(2+3);

浏览按钮事件处理程序：

        private void button_browse_Click(object sender,EventArgs e)
        {
            OpenFileDialog fbd = new OpenFileDialog();
            fbd.Title = "请选择一个文件：";
            fbd.CheckFileExists = true;
            fbd.CheckPathExists = true;
            fbd.Filter = "*.txt(文本文件)|*.txt|*.*(所有文件)|*.*";
            fbd.FileName = Environment.GetFolderPath(Environment.SpecialFolder.MyComputer);
            if (fbd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
                textBox_sav