/// <summary>
/// Implementation of IPostBackDataHandler.LoadPostData().
/// This method examines the postback data and updates the control's state.
/// </summary>
/// <param name="postDataKey">Provides the dictionary key for the control instance.</param>
/// <param name="postCollection">A dictionary collection of all incoming form values.</param>
/// <returns>True if the control's state changes.</returns>
/// <remarks>If this method returns true, the .NET framework will call RaisePostDataChangedEvent().
///
/// Because this is effectively a composite control with the potential for multiple fields
/// being returned, the postDataKey parameter is ignored.</remarks>
public bool LoadPostData(string postDataKey, NameValueCollection postCollection)
{
selectAction action = GetSelectAction(postCollection);
bool StateHasChanged;
if (action != selectAction.None)
{
StateHasChanged = ProcessSelectionAction(action, postCollection);
}
else
{
StateHasChanged = ProcessAsynchronousAction(postCollection);
}
return(StateHasChanged);
}
/// <summary>
/// Helper function to process the select/remove operation and update the control's state.
/// </summary>
/// <param name="action">Specifies whether items are being selected or removed.</param>
/// <param name="postData">A dictionary collection of all incoming form values.</param>
/// <returns>True if the action results in a state change, false if no change has occured.</returns>
/// <remarks>It is possible for this method to return false if the impact of a selection
/// action is that no change has occured. For example, if the user clicks the "Remove" button, but
/// the only items selected are in the Additions list.</remarks>
private bool ProcessSelectionAction(selectAction action, NameValueCollection postData)
{
bool selectionHasChanged = false;
string[] selections = null;
string selectKey =
BuildUniqueControlName((action == selectAction.Select) ? _leftSelectName : _rightSelectName);
if ((selections = postData.GetValues(selectKey)) != null)
{
foreach (ListItem item in Items)
{
if (Array.Find(selections, delegate(string s) { return(s == item.Text); }) != null)
{
// Mark the item selected or unselected based on the current action.
item.Selected = (action == selectAction.Select);
selectionHasChanged = true;
}
}
}
return(selectionHasChanged);
}
