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Event sequence

The API and event sequence and lifecycle of RadGrid are quite similar to MS DataGrid/GridView. The sequence of the events is as follows.

RadGrid with EnableViewState set to true (default value)

First page load

  1. Page.Load
  2. Grid_Instance.NeedDataSource
  3. ItemCreated for each item
  4. ItemDataBound for each item
  5. Page.PreRender

Normal postback from a control outside of RadGrid

  1. ItemCreated for each item
  2. Page.Load
  3. Postback Events
  4. Page.PreRender

On server selection from Select/Deselect GridButtonColumn/Auto Postback on row click

  1. ItemCreated for each item
  2. Page.Load
  3. ItemCommand
  4. SelectedIndexChanged
  5. Other postback events
  6. Page.PreRender

On edit/update/insert/delete action or paging/sorting/grouping/filtering operation

  1. ItemCreated for each item
  2. Page.Load
  3. Grid_Instance.ItemCommand
  4. Grid_Instance.EditCommand/UpdateCommand/InsertCommand or GridInstance.PageIndexChanged/SortCommand/GroupsChanging/ItemCommand
  5. Grid_Instance.NeedDataSource
  6. ItemCreated for each item
  7. ItemDataBound for each item
  8. Page.PreRender

Calling Rebind()

Invoking the Rebind() method from a postback event handler of an outside control or RadGrid will raise the NeedDataSource event. Then grid items will be recreated so the ItemCreated and ItemDataBound events will be raised according to the cases above.

With hierarchy

  1. Page_Load
  2. NeedDataSource
  3. DetailTableDataBind

After the NeedDataSource event, the DetailTableDataBind is raised for each detail item that will be bound. You can use the e.IsFromDetailTable flag in NeedDataSource to check where the call originates from, so you can fetch data only when necessary.

Which items are bound depends on the HierarchyLoadMode property. For example, if it is set to Client, all detail items will be bound initially on the server so they can be expanded on the client.

If you set the RetainExpandStateOnRebind property to true and the HierarchyLoadMode to Client, the NeedDataSource and DetailTableDataBind events will be raised first for the items that need to be expanded. These events will come before Page_Load, whether you rebind the grid or not because the items need to be created so their Expanded property can be set to true.

  1. NeedDataSource for expanded items
  2. DetailTableDataBind for expanded items
  3. Page_Load
  4. NeedDataSource
  5. DetailTableDataBind

RadGrid with EnableViewState set to false

First page load

  1. Page.Load
  2. Grid_Instance.NeedDataSource
  3. ItemCreated for each Item
  4. ItemDataBound for each Item
  5. Page.PreRender

Normal postback from a control outside of RadGrid

  1. Page.Load
  2. Grid_Instance.NeedDataSource
  3. ItemCreated for each Item
  4. ItemDataBound for each Item
  5. Postback Events
  6. Page.PreRender

On server selection from Select/Deselect GridButtonColumn/Auto Postback on row click

  1. Page.Load
  2. Grid_Instance.NeedDataSource
  3. ItemCreated for each Item
  4. ItemDataBound for each Item
  5. ItemCommand
  6. SelectedIndexChanged
  7. Other postback events
  8. Page.PreRender

On edit/update/insert/delete action or paging/sorting/grouping/filtering operation

  1. ItemCreated for each Item
  2. Page.Load
  3. GridInstance.NeedDataSource
  4. ItemCreated for each Item
  5. ItemDataBound for each Item
  6. GridInstance.ItemCommand
  7. Grid_Instance.EditCommand/UpdateCommand/InsertCommand or GridInstance.PageIndexChanged/SortCommand/GroupsChanging/ItemCommand
  8. ItemCreated for each Item
  9. ItemDataBound for each Item
  10. Page.PreRender

Calling Rebind()

Invoking the Rebind() method from a postback event handler of an outside control or RadGrid will not raise the NeedDataSource event. Then grid items will be recreated so the ItemCreated and ItemDataBound events will be raised according to the cases above.

To see how to rebind the grid in this case, review the Rebind Grid with EnableViewState = false article.

See Also

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