在ASP.NET中使用實體框架在Gridview中級聯DropdownList

Question

我想在GridView控件內部實現級聯DropDownList。我的代碼是下面給出：

的.aspx代碼

<asp:GridView ID="GridView1" runat="server" Width="550px" 
     AutoGenerateColumns="False" OnRowDataBound="GridView1_RowDataBound"> 

     <Columns> 


      <asp:TemplateField HeaderText="State"> 
       <ItemTemplate> 
        <asp:DropDownList ID="DropDownList1" 
         AutoPostBack="true" runat="server" DataTextField="State" DataValueField="StateID" onselectedindexchanged="DropDownList1_SelectedIndexChanged"> 
        </asp:DropDownList> 
       </ItemTemplate> 
      </asp:TemplateField> 

      <asp:TemplateField HeaderText="City"> 
       <ItemTemplate> 
        <asp:DropDownList ID="DropDownList2" 
         AutoPostBack="true" runat="server" DataTextField="City" DataValueField="CityId"> 
        </asp:DropDownList> 
       </ItemTemplate> 
      </asp:TemplateField> 

代碼背後：

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e) 
    { 
     if (e.Row.RowType == DataControlRowType.DataRow) 
     { 
      DropDownList ddl1 = e.Row.FindControl("DropDownList1") as DropDownList; 
      if (ddl1 != null) 
      { 
       using (var context = new ABCEntities()) 
       { 
        var _state= from u in context.State 
             select new 
             { 
              StateId= u.StateId, 
              State= u.State 

             }; 
        ddl1.DataSource =_state.ToList(); 
        ddl1.DataValueField = "StateId"; 
        ddl1.DataTextField = "State"; 
        ddl1.DataBind(); 
        ddl1.Items.Insert(0, new ListItem("--Select--", "0")); 

       } 

      } 
     } 
    } 



protected void DropDownList1_SelectedIndexChanged(object sender, System.EventArgs e) 
    { 
     DropDownList ddl1 = (DropDownList)sender; 
     GridViewRow row = (GridViewRow)ddl1.NamingContainer; 
     if (row != null) 
     { 
      DropDownList ddl2 = (DropDownList)row.FindControl("DropDownList2"); 
      ddl2.DataSource = GetDataForSecondDropDownList(Convert.ToInt32(ddl1.SelectedValue)); 
      ddl2.DataTextField = "CityID"; 
      ddl2.DataValueField = "City"; 
      ddl2.DataBind(); 
     } 
    } 

    public GetDataForSecondDropDownList(int ID) 
    {    
     using (var context = new ABCEntities()) 
     { 
      var _city = (from u in context.Cities 
         where u.StateID == ID 
         select new 
         { 
          CityID = u.CityID, 
          City= u.City 

         }).Distinct(); 
     } 

     return;   // How do i return this method 

    } 

我有一個如何STATEID傳遞到一個問題方法GetDataForSecondDropDownList（）並返回相關數據以上代碼。

請幫幫我。提前感謝你。

Answer 1

您需要

1. 爲你的「城市」對象創建一個對象類型
2. 聲明你的方法用的IEnumerable返回類型
3. 把你的回報using塊內

因此，爲City對象添加一個私人類（如果需要，請在您當前的代碼後面的代碼中）：

private class City 
{ 
    public int CityID { get; set; } 
    public string City { get; set; } 

    public City(int cityID, string city) 
    { 
     CityID = cityID; 
     City = city; 
    } 
} 

然後修改方法如下：

public IEnumerable<City> GetDataForSecondDropDownList(int ID) 
{    
    using (var context = new ABCEntities()) 
    { 
     var _city = (from u in context.Cities 
        where u.StateID == ID 
        select new City 
        { 
         CityID = u.CityID, 
         City= u.City 

        }).Distinct(); 

     return _city; 
    } 
}