How cani pass the parameter dynamically in Linq?

private List<string> GetAllFieldValues(string p)
{
    List<string> field_values = new List<string>();
    string connectionString = ConfigurationManager.ConnectionStrings["SchoolContext"].ConnectionString;
    using (SqlConnection con = new SqlConnection(connectionString))
    {
        SqlCommand cmd = new SqlCommand();
        con.Open();
        cmd.CommandText = "SELECT " + p + " from tbl_student where institutionid=" + Convert.ToInt32(Session["institutionId"].ToString());
        cmd.Connection = con;
        SqlDataReader dr = cmd.ExecuteReader();
        if (dr.HasRows)
        {
            while (dr.Read())
            {
                if (p == "dateofadmission" || p == "dateofbirth")
                    field_values.Add(Convert.ToDateTime(dr[0].ToString()).ToShortDateString());
                else
                    field_values.Add(dr[0].ToString());
            }
        }
        else
        {

        }
    }
    return field_values;
}