What's X

   1:  using System.Data.Objects;//需要用到ObjectQuery

   2:   

   3:  namespace LinQ_to_Entity

   4:  {

   5:      public partial class fmMain : Form

   6:      {

   7:          private SchoolEntities schoolEntity;

   8:          public fmMain()

   9:          {

  10:              InitializeComponent();

  11:   

  12:              schoolEntity = new SchoolEntities();

  13:          }

  14:   

  15:          private void fmMain_Load(object sender, EventArgs e)

  16:          {

  17:              var query = from q in schoolEntity.Departments.Include("Courses")

  18:                                  select q;

  19:              //ObjectQuery<T>.Include 方法(指定要包含在查詢結果中的相關物件)

  20:              //※所以在查詢Departments時，會順便查詢Course(存放在Departments.Course的集合內)

  21:              cmbDepartment.DisplayMember = "Name";

  22:              cmbDepartment.DataSource = ((ObjectQuery)query).Execute(MergeOption.AppendOnly);

  23:              //MergeOption 列舉型別(指定載入物件內容中的物件如何與已經位於物件內容中的物件合併)

  24:          }

  25:   

  26:          private void cmbDepartment_SelectedIndexChanged(object sender, EventArgs e)

  27:          {

  28:              if (cmbDepartment.SelectedItem != null)

  29:              {

  30:                  Department department = (Department)cmbDepartment.SelectedItem;

  31:                  //因為在查詢Departments就已經把Courses連帶查詢好了，所以就只要指定department的Coures集合

  32:                  grdCourses.DataSource = department.Courses;

  33:              }

  34:          }

  35:   

  36:          private void btnSave_Click(object sender, EventArgs e)

  37:          {

  38:              schoolEntity.SaveChanges();//儲存異動資料

  39:          }

  40:      }

  41:  }