Web Layout Manager improvements and important changes in XAF v17.1

In the 17.1 version, we have improved the scenario of loading ASPxPageControl tab content when WebLayoutManager.DelayedItemsInitialization equals true and the Conditional Appearance module is involved:
ConditionalAppearance - How to avoid not fully initialized layout tab content when using Appearance rules with ViewItemVisibility.Hide on the Web. There are also several breaking changes in the initialization and usage of LayoutItemTemplateContainerBase descendants.

- If custom templates are used for laying out controls (only LayoutGroupTemplate and TabbedGroupTemplate descendants), it is necessary to call the LayoutItemTemplateContainerBase.Instantiate()  method before adding LayoutItemTemplateContainerBase descendants if WebLayoutManager.DelayedItemsInitialization equals true. For example:

C#
public class CustomLayoutGroupTemplate : LayoutGroupTemplate {  
    protected override void LayoutContentControls(LayoutGroupTemplateContainer layoutGroupTemplateContainer, IList<Control> controlsToLayout) {  
        foreach(Control control in controlsToLayout) {  
            LayoutItemTemplateContainerBase templateContainer = control as LayoutItemTemplateContainerBase;  
            if(templateContainer != null && templateContainer.LayoutManager.DelayedItemsInitialization) {  
                templateContainer.Instantiate();  
            }  
            layoutGroupTemplateContainer.Controls.Add(control);  
        }  
    }  
}  

Visual Basic
Public Class CustomLayoutGroupTemplate  
    Inherits LayoutGroupTemplate  
    Protected Overrides Sub LayoutContentControls(layoutGroupTemplateContainer As LayoutGroupTemplateContainer, controlsToLayout As IList(Of Control))  
        For Each control As Control In controlsToLayout  
            Dim templateContainer As LayoutItemTemplateContainerBase = TryCast(control, LayoutItemTemplateContainerBase)  
            If templateContainer IsNot Nothing AndAlso templateContainer.LayoutManager.DelayedItemsInitialization Then  
                templateContainer.Instantiate()  
            End If  
            layoutGroupTemplateContainer.Controls.Add(control)  
        Next  
    End Sub  
End Class  

- If a LayoutItemTemplateContainer is created in the WebLayoutManager descendant, then it is necessary to set the LayoutItemTemplateContainer.ViewItem and LayoutItemTemplateContainer.Template properties. For example:

C#
public class CustomWebLayoutManager : WebLayoutManager {  
    protected override LayoutItemTemplateContainer LayoutItem(ViewItemsCollection viewItems, IModelLayoutViewItem layoutItemModel) {  
        LayoutItemTemplateContainer templateContainer = new LayoutItemTemplateContainer(this, viewItems, layoutItemModel);  
        templateContainer.ViewItem = viewItems[layoutItemModel.ViewItem.Id];  
        templateContainer.Template = LayoutItemTemplate;  
        ...  
        return templateContainer;  
    }  
}  

Visual Basic
Public Class CustomWebLayoutManager  
    Inherits WebLayoutManager  
    Protected Overrides Function LayoutItem(viewItems As ViewItemsCollection, layoutItemModel As IModelLayoutViewItem) As LayoutItemTemplateContainer  
        Dim templateContainer As New LayoutItemTemplateContainer(Me, viewItems, layoutItemModel)  
        templateContainer.ViewItem = viewItems(layoutItemModel.ViewItem.Id)  
        templateContainer.Template = LayoutItemTemplate  
        ...  
        Return templateContainer  
    End Function  
End Class  

- If a LayoutGroupTemplateContainer is created in the WebLayoutManager descendant, then it is necessary to set the LayoutGroupTemplateContainer.Template property. For example:

C#
public class CustomWebLayoutManager : WebLayoutManager {  
    protected override LayoutGroupTemplateContainer ProcessStandardGroup(ViewItemsCollection viewItems, IModelLayoutGroup layoutGroupModel) {  
        ImageInfo headerImageInfo = ImageLoader.Instance.GetImageInfo(layoutGroupModel.ImageName);  
        LayoutGroupTemplateContainer templateContainer = new LayoutGroupTemplateContainer(this, viewItems, layoutGroupModel, headerImageInfo);  
        templateContainer.Template = LayoutGroupTemplate;  
        ...  
        return templateContainer;  
    }  
}  

Visual Basic
Public Class CustomWebLayoutManager  
    Inherits WebLayoutManager  
    Protected Overrides Function ProcessStandardGroup(viewItems As ViewItemsCollection, layoutGroupModel As IModelLayoutGroup) As LayoutGroupTemplateContainer  
        Dim headerImageInfo As ImageInfo = ImageLoader.Instance.GetImageInfo(layoutGroupModel.ImageName)  
        Dim templateContainer As New LayoutGroupTemplateContainer(Me, viewItems, layoutGroupModel, headerImageInfo)  
        templateContainer.Template = LayoutGroupTemplate  
        ...  
        Return templateContainer  
    End Function  
End Class  

- If a TabbedGroupTemplateContainer is created in the WebLayoutManager descendant, then it is necessary to set the TabbedGroupTemplateContainer.Template property. For example:

C#
public class CustomWebLayoutManager : WebLayoutManager {  
    protected override TabbedGroupTemplateContainer ProcessTabbedGroup(ViewItemsCollection viewItems, IModelTabbedGroup layoutGroupModel) {  
        TabbedGroupTemplateContainer templateContainer = new TabbedGroupTemplateContainer(this, viewItems, layoutGroupModel);  
        templateContainer.Template = TabbedGroupTemplate;  
        ...  
        return templateContainer;  
    }  
}  

Visual Basic
Public Class CustomWebLayoutManager  
    Inherits WebLayoutManager  
    Protected Overrides Function ProcessTabbedGroup(viewItems As ViewItemsCollection, layoutGroupModel As IModelTabbedGroup) As TabbedGroupTemplateContainer  
        Dim templateContainer As New TabbedGroupTemplateContainer(Me, viewItems, layoutGroupModel)  
        templateContainer.Template = TabbedGroupTemplate  
        ...  
        Return templateContainer  
    End Function  
End Class