Hi ,

Im switching from vb to c# and have syntax errors in this piece of code, which I couldnt figure out what. Any help pls? thanks

Code:
namespace arraystringcheck
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        string grades;
        int mark;
        private void button1_Click(object sender, EventArgs e)

        {  
            string[] grade ={ "Pass", "Merit", "Fail" };
            
            foreach (Control c in this.controls)
            {
                if ((typeof (c is TextBox )) && (textbox.Text != null) 
                {
                if (string m in grade)
                 {
                    switch (grades)
                    {
                       case "Merit":
                            mark += 10; 
                        case "Pass":
                            mark += 5;                        
                        case "Fail":
                            mark = mark;

                        default:
                            MessageBox.show ("grade is Invalid");           
                    }                
            }
            
        }label1.Text= mark.ToString;
        }
    }
}