RadGrid 在行扩展时填充数据源？

Question

我在 RadGrid 中有一个嵌套视图，下面是我的代码隐藏。 Grid 正在请求每一行的详细信息，但是我希望它仅在该行实际展开时才请求详细信息？

Private Sub RadGrid1_NeedDataSource(ByVal source As Object, ByVal e As GridNeedDataSourceEventArgs) Handles dataGridMyLeads.NeedDataSource
    If Not e.IsFromDetailTable Then
        Dim DS = (PersonList.GetFilteredLeads(MySession.RiseEID, MySession.RiseClientID, , , MySession.ShowAll)).OrderBy(Function(c) c.LastAction)
        If RouteData.Values("Cat") = "StatusOverdue" Then DS = DS.Where(Function(c) c.NextAction >= Now())
        dataGridMyLeads.DataSource = DS
    End If
End Sub

Protected Sub RadGrid1_PreRender(ByVal sender As Object, ByVal e As EventArgs) Handles dataGridMyLeads.PreRender
    If Not Page.IsPostBack Then
        dataGridMyLeads.MasterTableView.Items(0).ChildItem.FindControl("InnerContainer").Visible = True
    End If
End Sub

Protected Sub RadGrid1_ItemCommand(ByVal source As Object, ByVal e As GridCommandEventArgs) Handles dataGridMyLeads.ItemCommand
    If (e.CommandName = "RowClick" OrElse e.CommandName = "ExpandCollapse") And TypeOf e.Item Is GridDataItem Then
        DirectCast(e.Item, GridDataItem).ChildItem.FindControl("InnerContainer").Visible = Not e.Item.Expanded
    End If
    If e.CommandName = "RowClick" OrElse e.CommandName = "ExpandCollapse" Then
        e.Item.Expanded = Not e.Item.Expanded
    End If
    If e.CommandName = "RowClick" OrElse e.CommandName = "ExpandCollapse" Then
        Dim item As GridItem
        For Each item In e.Item.OwnerTableView.Items
            If item.Expanded AndAlso Not item Is e.Item Then
                item.Expanded = False
            End If
        Next item
    End If
End Sub

Protected Sub RadGrid1_ItemCreated(ByVal sender As Object, ByVal e As GridItemEventArgs) Handles dataGridMyLeads.ItemCreated
    If TypeOf e.Item Is GridNestedViewItem Then
        e.Item.FindControl("InnerContainer").Visible = (DirectCast(e.Item, GridNestedViewItem)).ParentItem.Expanded
    End If
End Sub

Answer 1

RadGrid 已经有了 DetailTables，所以你所要做的就是 -

1. HierarchyDefaultExpanded="false"
2. HierarchyLoadMode="ServerOnDemand"

Grid - Programmatic Hierarchy Binding

示例

<telerik:RadGrid runat="server" ID="RadGrid1"
    AutoGenerateColumns="false"
    OnNeedDataSource="RadGrid1_NeedDataSource"
    OnDetailTableDataBind="RadGrid1_DetailTableDataBind">
    <MasterTableView
        DataKeyNames="CountryId"
        HierarchyDefaultExpanded="false"
        HierarchyLoadMode="ServerOnDemand">
        <Columns>
            <telerik:GridBoundColumn
                DataField="Name"
                UniqueName="Name"
                HeaderText="Country">
            </telerik:GridBoundColumn>
        </Columns>
        <DetailTables>
            <telerik:GridTableView 
                DataKeyNames="StateId" 
                Name="States" 
                AutoGenerateColumns="False">
                <Columns>
                    <telerik:GridBoundColumn
                        DataField="Name"
                        UniqueName="Name"
                        HeaderText="State">
                    </telerik:GridBoundColumn>
                </Columns>
            </telerik:GridTableView>
        </DetailTables>
    </MasterTableView>
</telerik:RadGrid>

代码隐藏

protected void RadGrid1_NeedDataSource(object source, 
   GridNeedDataSourceEventArgs e)
{
    RadGrid1.DataSource = Countries;
}

protected void RadGrid1_DetailTableDataBind(object source, 
   GridDetailTableDataBindEventArgs e)
{
    GridDataItem item = e.DetailTableView.ParentItem;

    int countryId = Convert.ToInt32(item.GetDataKeyValue("CountryId"));

    e.DetailTableView.DataSource = Countries
        .First(c => c.CountryId == countryId)
        .States;
}

public class Country
{
    public int CountryId { get; set; }
    public string Name { get; set; }

    public ICollection<State> States { get; set; }

    public Country()
    {
        States = new List<State>();
    }
}

public class State
{
    public int StateId { get; set; }
    public string Name { get; set; }
}

private List<Country> Countries
{
    get
    {
        return new List<Country>
        {
            new Country
            {
                CountryId = 1,
                Name = "United States",
                States = new List<State>
                {
                    new State {StateId = 1, Name = "Alabama"},
                    new State {StateId = 2, Name = "Alaska"},
                    new State {StateId = 3, Name = "Arkansas"},
                },
            },
            new Country
            {
                CountryId = 1,
                Name = "Canada",
                States = new List<State>
                {
                    new State {StateId = 4, Name = "Alberta"},
                    new State {StateId = 5, Name = "British Columbia"},
                    new State {StateId = 6, Name = "Manitoba"},
                },
            },
        };
    }
}