private void insertbtn_Click(object sender, EventArgs e)
        {
            string name = textBox1.Text.ToString();
            string course;
 
            for (int i = 0; i < checkedListBox1.CheckedItems.Count; i++)
            {
                course += checkedListBox1.CheckedItems[i].ToString() + " ";
            }
 
 
            string constring = "PROVIDER= MSDAORA;USER ID = SYSTEM; PASSWORD = mca";
            string query = "insert into checkapp1 values('" + name + "','" + course+ "')";
            cn = new OleDbConnection(constring);
            cn.Open();
            cm = new OleDbCommand(query, cn);
            cm.ExecuteNonQuery();
            MessageBox.Show("data inserted");
        }

string s;
s += "abc";

string s = string.Empty;
s += "abc";