ASP.NET Gridview 中的级联下拉列表答案

【问题标题】：Cascading DropdownList in Gridview in ASP.NETASP.NET Gridview 中的级联下拉列表
【发布时间】：2014-01-12 02:21:24
【问题描述】：

我将在 GridView 控件中实现级联 DropDownList。我的代码如下：

页面：

<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>

代码隐藏：

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 IEnumerable<City> GetDataForSecondDropDownList(int ID)        //Getting Error
{            
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;
}

}

我收到一条错误消息：错误：可访问性不一致：返回类型“System.Collections.Generic.IEnumerable”比方法“.......GetDataForSecondDropDownList(int)”更难访问

我该怎么办，请帮帮我。提前致谢。

【问题讨论】：

标签： asp.net entity-framework c#-4.0 entity-framework-4

【解决方案1】：

该错误表明City 类难以访问。可能它是私有的或受保护的。确保您已像这样将其声明为公开：

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

【讨论】：