How to: Extend and Access the Application Model Nodes from Controllers

Oct 18, 2022
8 minutes to read

To demonstrate how to extend the Application Model, this topic details how to display a Group Footer for List Views. An IsGroupFooterVisible property will be added to the to the Views | <ListView> node. When set to true for a ListView, a special Controller will enable the group footer. To specify a summary type for different columns, a GroupFooterSummaryType property will be added to the ListView | Columns | Column node. For general information on extending the Application Model, refer to the Extend and Customize the Application Model in Code help topic.

Tip

A complete sample project is available in the DevExpress Code Examples database at https://supportcenter.devexpress.com/ticket/details/e213/how-to-extend-the-application-model.

Implement the interfaces exposing the IsGroupFooterVisible and GroupFooterSummaryType properties.

C#
VB.NET

using DevExpress.Data;
using System.ComponentModel;
//...
public interface IModelListViewExtender {
    bool IsGroupFooterVisible { get; set; }
}
public interface IModelColumnExtender {
    [DefaultValue(SummaryItemType.None)]
    SummaryItemType GroupFooterSummaryType { get; set; }
}

Imports DevExpress.Data
Imports System.ComponentModel
'...
Public Interface IModelListViewExtender
    Property IsGroupFooterVisible() As Boolean
End Interface
Public Interface IModelColumnExtender
    <DefaultValue(SummaryItemType.None)> _
    Property GroupFooterSummaryType() As SummaryItemType
End Interface

Override the ModuleBase.ExtendModelInterfaces method of your base Module to extend the Application Model with declared interfaces.

C#
VB.NET

using DevExpress.ExpressApp.Model;
// ...
public sealed partial class ExtendModelModule : ModuleBase {
    // ...
    public override void ExtendModelInterfaces(ModelInterfaceExtenders extenders) {
        base.ExtendModelInterfaces(extenders);
        extenders.Add<IModelListView, IModelListViewExtender>();
        extenders.Add<IModelColumn, IModelColumnExtender>();
    }
}

Imports DevExpress.ExpressApp.Model
'...
Public NotInheritable Partial Class ExtendModelModule
    Inherits ModuleBase
    '...
    Public Overrides Sub ExtendModelInterfaces(ByVal extenders As ModelInterfaceExtenders)
        MyBase.ExtendModelInterfaces(extenders)
        extenders.Add(Of IModelListView, IModelListViewExtender)()
        extenders.Add(Of IModelColumn, IModelColumnExtender)()
    End Sub
End Class

Create a WinGroupFooterViewController ViewController in the Windows Forms Module. Inherit it from the ViewController<ListView> type, since this Controller must be activated in List Views only.

Override the protected OnViewControlsCreated method to display the group footer, if the IsGroupFooterVisible property is set to true for the current List View. Additionally, when the Controller is activated, handle the View.ModelSaved event to save the group footer summary type for different columns into Application Model, when the current List View is closing.

C#
VB.NET

using System;
using DevExpress.Data;
using DevExpress.ExpressApp;
using DevExpress.ExpressApp.Model;
using DevExpress.ExpressApp.Win.Editors;
using DevExpress.XtraGrid.Views.Grid;
using DevExpress.XtraGrid.Columns;
//...
public class WinGroupFooterViewController : ViewController<ListView> {
    private void View_ModelSaved(object sender, EventArgs e) {
        IModelListViewExtender modelListView = View.Model as IModelListViewExtender;
        if(modelListView != null && modelListView.IsGroupFooterVisible) {
            GridListEditor gridListEditor = View.Editor as GridListEditor;
            if(gridListEditor != null) {
                GridView gridView = gridListEditor.GridView;
                for(int i = 0; i < gridView.GroupSummary.Count; i++) {
                    IModelColumnExtender modelColumn = View.Model.Columns[
                        gridView.GroupSummary[i].FieldName] as IModelColumnExtender;
                    if(modelColumn != null) {
                        modelColumn.GroupFooterSummaryType = gridView.GroupSummary[i].SummaryType;
                    }
                }
            }
        }
    }
    protected override void OnViewControlsCreated() {
        base.OnViewControlsCreated();
        IModelListViewExtender modelListView = View.Model as IModelListViewExtender;
        if(modelListView != null && modelListView.IsGroupFooterVisible) {
            GridListEditor gridListEditor = View.Editor as GridListEditor;
            if(gridListEditor != null) {
                GridView gridView = gridListEditor.GridView;
                gridView.OptionsView.GroupFooterShowMode = GroupFooterShowMode.VisibleAlways;
                foreach(IModelColumn modelColumn in View.Model.Columns) {
                    IModelColumnExtender modelColumnExtender = modelColumn as IModelColumnExtender;
                    if(modelColumnExtender != null && 
                        modelColumnExtender.GroupFooterSummaryType != SummaryItemType.None) {
                        GridColumn gridColumn = gridView.Columns[
                            modelColumn.ModelMember.MemberInfo.BindingName];
                        gridView.GroupSummary.Add(modelColumnExtender.GroupFooterSummaryType, 
                            modelColumn.Id, gridColumn);
                    }
                }
            }
        }
    }
    protected override void OnActivated() {
        base.OnActivated();
        View.ModelSaved += View_ModelSaved;
    }
    protected override void OnDeactivated() {
        View.ModelSaved -= View_ModelSaved;
        base.OnDeactivated();
    }
}

Imports Microsoft.VisualBasic
Imports System
Imports DevExpress.Data
Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Model
Imports DevExpress.ExpressApp.Win.Editors
Imports DevExpress.XtraGrid.Views.Grid
Imports DevExpress.XtraGrid.Columns
'...
Public Class WinGroupFooterViewController
    Inherits ViewController(Of ListView)
    Private Sub View_ModelSaved(ByVal sender As Object, ByVal e As EventArgs)
        Dim modelListView As IModelListViewExtender = TryCast(View.Model, IModelListViewExtender)
        If modelListView IsNot Nothing AndAlso modelListView.IsGroupFooterVisible Then
            Dim gridListEditor As GridListEditor = TryCast(View.Editor, GridListEditor)
            If gridListEditor IsNot Nothing Then
                Dim gridView As GridView = gridListEditor.GridView
                For i As Integer = 0 To gridView.GroupSummary.Count - 1
                    Dim modelColumn As IModelColumnExtender = TryCast(CType(View.Model.Columns, _
                    IModelList(of IModelColumn))(gridView.GroupSummary(i).FieldName), _
                    IModelColumnExtender)
                    If modelColumn IsNot Nothing Then
                        modelColumn.GroupFooterSummaryType = gridView.GroupSummary(i).SummaryType
                    End If
                Next i
            End If
        End If
    End Sub
    Protected Overrides Overloads Sub OnViewControlsCreated()
        MyBase.OnViewControlsCreated()
        Dim modelListView As IModelListViewExtender = TryCast(View.Model, IModelListViewExtender)
        If modelListView IsNot Nothing AndAlso modelListView.IsGroupFooterVisible Then
            Dim gridListEditor As GridListEditor = TryCast(View.Editor, GridListEditor)
            If gridListEditor IsNot Nothing Then
                Dim gridView As GridView = gridListEditor.GridView
                gridView.OptionsView.GroupFooterShowMode = GroupFooterShowMode.VisibleAlways
                For Each modelColumn As IModelColumn In View.Model.Columns
                    Dim modelColumnExtender As IModelColumnExtender = _
                    TryCast(modelColumn, IModelColumnExtender)
                    If modelColumnExtender IsNot Nothing AndAlso _
                    modelColumnExtender.GroupFooterSummaryType <> SummaryItemType.None Then
                        Dim gridColumn As GridColumn = _
                        gridView.Columns(modelColumn.ModelMember.MemberInfo.BindingName)
                        gridView.GroupSummary.Add( _
                        modelColumnExtender.GroupFooterSummaryType, modelColumn.Id, gridColumn)
                    End If
                Next modelColumn
            End If
        End If
    End Sub
    Protected Overrides Overloads Sub OnActivated()
        MyBase.OnActivated()
        AddHandler View.ModelSaved, AddressOf View_ModelSaved
    End Sub
    Protected Overrides Overloads Sub OnDeactivated()
        RemoveHandler View.ModelSaved, AddressOf View_ModelSaved
        MyBase.OnDeactivated()
    End Sub
End Class

Create a WebGroupFooterViewController ViewController in the ASP.NET Web Forms Module. Inherit it from the ViewController<ListView> type, since this Controller must be activated in List Views only.

Override the protected OnViewControlsCreated method to display the group footer, if the IsGroupFooterVisible property is set to true for the current List View. There is no need to handle the ModelSaved event since end-users cannot customize summary types for different columns in the ASP.NET Web Forms UI.

C#
VB.NET

using System;
using DevExpress.Data;
using DevExpress.ExpressApp;
using DevExpress.ExpressApp.Model;
using DevExpress.ExpressApp.Web.Editors.ASPx;
using DevExpress.Web;
//...
public class WebGroupFooterViewController : ViewController<ListView> {
    protected override void OnViewControlsCreated() {
        base.OnViewControlsCreated();
        IModelListViewExtender modelListView = View.Model as IModelListViewExtender;
        if(modelListView != null && modelListView.IsGroupFooterVisible) {
            ASPxGridListEditor gridListEditor = View.Editor as ASPxGridListEditor;
            if(gridListEditor != null) {
                ASPxGridView gridView = gridListEditor.Grid;
                gridView.Settings.ShowGroupFooter = GridViewGroupFooterMode.VisibleAlways;
                foreach(IModelColumn modelColumn in View.Model.Columns) {
                    IModelColumnExtender modelColumnExtender = modelColumn as IModelColumnExtender;
                    if(modelColumnExtender != null && 
                        modelColumnExtender.GroupFooterSummaryType != SummaryItemType.None) {
                        string fieldName = modelColumn.ModelMember.MemberInfo.BindingName.ToUpper();
                        ASPxSummaryItem summaryItem = null;
                        foreach(ASPxSummaryItem currentItem in gridView.GroupSummary) {
                            if(currentItem.FieldName.ToUpper() == fieldName) {
                                currentItem.ShowInGroupFooterColumn = modelColumn.Caption;
                                summaryItem = currentItem;
                                break;
                            }
                        }
                        if(summaryItem == null) {
                            summaryItem = new ASPxSummaryItem(
                                fieldName, modelColumnExtender.GroupFooterSummaryType);
                            summaryItem.ShowInGroupFooterColumn = modelColumn.Caption.ToUpper();
                            gridView.GroupSummary.Add(summaryItem);
                        }
                    }
                }
            }
        }
    }
}

Imports Microsoft.VisualBasic
Imports System
Imports DevExpress.Data
Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Model
Imports DevExpress.ExpressApp.Web.Editors.ASPx
Imports DevExpress.Web
'...
Public Class WebGroupFooterViewController
    Inherits ViewController(Of ListView)
    Protected Overrides Sub OnViewControlsCreated()
        MyBase.OnViewControlsCreated()
        Dim modelListView As IModelListViewExtender = TryCast(View.Model, IModelListViewExtender)
        If modelListView IsNot Nothing AndAlso modelListView.IsGroupFooterVisible Then
            Dim gridListEditor As ASPxGridListEditor = TryCast(View.Editor, ASPxGridListEditor)
            If gridListEditor IsNot Nothing Then
                Dim gridView As ASPxGridView = gridListEditor.Grid
                gridView.Settings.ShowGroupFooter = GridViewGroupFooterMode.VisibleAlways
                For Each modelColumn As IModelColumn In View.Model.Columns
                    Dim modelColumnExtender As IModelColumnExtender = _
                    TryCast(modelColumn, IModelColumnExtender)
                    If modelColumnExtender IsNot Nothing AndAlso _
                    modelColumnExtender.GroupFooterSummaryType <> SummaryItemType.None Then
                        Dim fieldName As String = modelColumn.ModelMember.MemberInfo.BindingName
                        Dim summaryItem As ASPxSummaryItem = Nothing
                        For Each currentItem As ASPxSummaryItem In gridView.GroupSummary
                            If currentItem.FieldName = fieldName Then
                                currentItem.ShowInGroupFooterColumn = modelColumn.Caption
                                summaryItem = currentItem
                                Exit For
                            End If
                        Next currentItem
                        If summaryItem Is Nothing Then
                            summaryItem = New ASPxSummaryItem( _
                            fieldName, modelColumnExtender.GroupFooterSummaryType)
                            summaryItem.ShowInGroupFooterColumn = modelColumn.Caption
                            gridView.GroupSummary.Add(summaryItem)
                        End If
                    End If
                Next modelColumn
            End If
        End If
    End Sub
End Class

Create a BlazorGroupFooterViewController ViewController in the ASP.NET Core Blazor Module. Inherit it from the ViewController<ListView> type, since this Controller must be activated in List Views only.

using DevExpress.ExpressApp;
using DevExpress.ExpressApp.Blazor.Editors.Grid;
using MainDemo.Module.BusinessObjects;
// ...
public class BlazorGroupFooterViewController : ViewController<ListView> {
    protected override void OnViewControlsCreated() {
        base.OnViewControlsCreated();
        if (View.Model is IModelListViewExtender modelListView) {
            if (modelListView.IsGroupFooterVisible && View.Editor is GridListEditor gridListEditor) {
                IDxDataGridAdapter dataGridAdapter = gridListEditor.GetDataGridAdapter();
                dataGridAdapter.DataGridModel.GroupSummary = DataGridGroupFooterSummary.Create(View.Model.Columns);
            }
        }
    }
}

Create a DataGridGroupFooterSummary Razor component in the ASP.NET Core Blazor Module and set its Build Action property to Content.

Razor

@using DevExpress.Blazor
@using DevExpress.ExpressApp.Model
@using MainDemo.Module.BusinessObjects

@foreach (IModelColumn modelColumn in ModelColumns) {
    if (modelColumn is IModelColumnExtender modelColumnExtender) {
        if (modelColumnExtender.GroupFooterSummaryType != DevExpress.Data.SummaryItemType.None) {
            <DxDataGridSummaryItem Field=@modelColumn.ModelMember.MemberInfo.BindingName
                                SummaryType=ConvertSummaryItemType(modelColumnExtender.GroupFooterSummaryType)
                                GroupSummaryPosition=GroupSummaryPosition.GroupFooter />
        }
    }
}

@code {
    [Parameter] 
    public IModelColumns ModelColumns { get; set; }
    public static RenderFragment Create(IModelColumns modelColumns) {
        return@<DataGridGroupFooterSummary ModelColumns=modelColumns />;
    }
    private SummaryItemType ConvertSummaryItemType(DevExpress.Data.SummaryItemType summaryItemType) {
        return summaryItemType switch {
            DevExpress.Data.SummaryItemType.Sum => SummaryItemType.Sum,
            DevExpress.Data.SummaryItemType.Average => SummaryItemType.Avg,
            DevExpress.Data.SummaryItemType.Count => SummaryItemType.Count,
            DevExpress.Data.SummaryItemType.Custom => throw new NotSupportedException(),
            DevExpress.Data.SummaryItemType.Max => SummaryItemType.Max,
            DevExpress.Data.SummaryItemType.Min => SummaryItemType.Min,
            DevExpress.Data.SummaryItemType.None => SummaryItemType.None,
            _ => SummaryItemType.None
        };
    }
}

Rebuild you solution and invoke the Model Editor for the base Module. Set a ListView node’s IsGroupPanelVisible property to true to be able to group the List View’s columns. Set the newly added IsGroupFooterVisible property to true. Specify summary types for the ListView node’s Column nodes.
Run the application. Display the List View with a group panel and group the List View by a column. The footer with the specified summary types will be displayed.

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