How to: Create Additional ListView Nodes in Code using a Generator Updater

• Sep 23, 2019
• 8 minutes to read

By default, two ListView nodes are generated in the Application Model for each business class. These nodes represent a general-purpose List View, and a Lookup List View that contains fewer columns (see List View Column Generation). Often, it is required to add more List Views manually. These additional List Views can be used as View Variants, Dashboard items, etc. Typically, this task can be accomplished in the Model Editor. However, in certain scenarios, adding nodes in code may be required. The default process of generating Views node’s child nodes is handled by the built-in ModelViewsNodesGenerator Nodes Generator. To customize this process, you should “attach” a Generator Updater class to this Generator. This topic describes how to implement a Generator Updater that creates custom ListView nodes. Additionally, an Updater that creates View Variants using these new nodes is illustrated. For details on Nodes Generators and Generator Updaters, refer to the Extend and Customize the Application Model in Code topic.

Note

Mobile applications do not support the View Variant, so the approach described in this topic is not supported by the Mobile platform.

Create List Views

Let us consider the following Employee business class.

C#

[DefaultClassOptions, ImageName("BO_Person")]
public class Employee : BaseObject {
    public Employee(Session session) : base(session) { }
    private string firstName;
    private string lastName;
    private string position;
    private string email;
    public string FirstName {
        get { return firstName; }
        set { SetPropertyValue(nameof(FirstName), ref firstName, value); }
    }
    public string LastName {
        get { return lastName; }
        set { SetPropertyValue(nameof(LastName), ref lastName, value); }
    }
    public string FullName {
        get { return String.Format("{0} {1}", FirstName, LastName); }
    }
    public string Position {
        get { return position; }
        set { SetPropertyValue(nameof(Position), ref position, value); }
    }
    public string Email {
        get { return email; }
        set { SetPropertyValue(nameof(Email), ref email, value); }
    }
}

VB.NET

<DefaultClassOptions, ImageName("BO_Person")> _
Public Class Employee
    Inherits BaseObject
    Public Sub New(ByVal session As Session)
        MyBase.New(session)
    End Sub
    Private _firstName As String
    Private _lastName As String
    Private _position As String
    Private _email As String
    Public Property FirstName() As String
        Get
            Return _firstName
        End Get
        Set(ByVal value As String)
            SetPropertyValue(NameOf(FirstName), _firstName, value)
        End Set
    End Property
    Public Property LastName() As String
        Get
            Return _lastName
        End Get
        Set(ByVal value As String)
            SetPropertyValue(NameOf(LastName), _lastName, value)
        End Set
    End Property
    Public ReadOnly Property FullName() As String
        Get
            Return String.Format("{0} {1}", FirstName, LastName)
        End Get
    End Property
    Public Property Position() As String
        Get
            Return _position
        End Get
        Set(ByVal value As String)
            SetPropertyValue(NameOf(Position), _position, value)
        End Set
    End Property
    Public Property Email() As String
        Get
            Return _email
        End Get
        Set(ByVal value As String)
            SetPropertyValue(NameOf(Email), _email, value)
        End Set
    End Property
End Class

The List View generated by default for this class is illustrated below.

This List View is defined by the Views | Employee_ListView node. Let us implement a Generator Updater that generates two additional List Views, which are:

1. A List View with hidden FirstName and LastName columns (Employee_ListView_FewColumns);
2. A List View where records are grouped by the Position column (Employee_ListView_Grouped).

A Generator Updater class should inherit the abstract ModelNodesGeneratorUpdater<T> class, where T is the type of the Nodes Generator to be customized. A built-in Nodes Generator that generates the Views node content is the ModelViewsNodesGenerator. The abstract ModelNodesGeneratorUpdater`1.UpdateNode method must be implemented in a custom Generator Updater. The parameter of the ModelNode type, passed to this method, represents a generated node. In our case, this node is the Views node. To add child nodes, the ModelNode.AddNode<T> method can be used. Note that the IModelObjectView.ModelClass property must be specified for each ListView node. After that, the ListView node properties can be accessed and their values can be customized. To access the Columns node, use the IModelListView.Columns property. The following snippet illustrates the AddListViewNodesGeneratorUpdater Generator Updater class.

C#

using DevExpress.ExpressApp.Model;
using DevExpress.ExpressApp.Model.Core;
using DevExpress.ExpressApp.Model.NodeGenerators;
// ...
public class AddListViewNodesGeneratorUpdater : 
    ModelNodesGeneratorUpdater<ModelViewsNodesGenerator> {
    public const string FewColumnsListViewNodeIdSuffix = "_FewColumns";
    string[] columnsToHideIds = { "FirstName", "LastName" };
    public const string GroupedListViewNodeIdSuffix = "_Grouped";
    public const string GroupByColumnId = "Position";
    static Type targetType = typeof(Employee);
    public override void UpdateNode(ModelNode viewsNode) {
        AddFewColumnsListViewNode(viewsNode);
        AddGroupedListViewNode(viewsNode);
    }
    public static IModelListView GetDefaultListView(ModelNode viewsNode) {
        return viewsNode.Application.BOModel.GetClass(targetType).DefaultListView;
    }
    IModelListView AddListViewNode(ModelNode viewsNode, string listViewId) {
        IModelListView listViewNode = (IModelListView)viewsNode.AddNode<IModelListView>(listViewId);
        listViewNode.ModelClass = viewsNode.Application.BOModel.GetClass(targetType);
        return listViewNode;
    }
    void AddFewColumnsListViewNode(ModelNode viewsNode) {
        string nodeId = GetDefaultListView(viewsNode).Id + FewColumnsListViewNodeIdSuffix;
        IModelListView fewColumnsListViewNode = AddListViewNode(viewsNode, nodeId);
        IModelColumns columns = (IModelColumns)fewColumnsListViewNode.Columns;
        foreach (string columnId in columnsToHideIds) {
            columns[columnId].Index = -1;
        }
    }
    void AddGroupedListViewNode(ModelNode viewsNode) {
        string nodeId = GetDefaultListView(viewsNode).Id + GroupedListViewNodeIdSuffix;
        IModelListView groupedListViewNode =
            AddListViewNode(viewsNode, nodeId);
        IModelColumns columns = (IModelColumns)groupedListViewNode.Columns;
        columns[GroupByColumnId].GroupIndex = 1;
    }
}

VB.NET

Imports DevExpress.ExpressApp.Model;
Imports DevExpress.ExpressApp.Model.Core;
Imports DevExpress.ExpressApp.Model.NodeGenerators;
' ...
Public Class AddListViewNodesGeneratorUpdater
    Inherits ModelNodesGeneratorUpdater(Of ModelViewsNodesGenerator)
    Public Const FewColumnsListViewNodeIdSuffix As String = "_FewColumns"
    Private columnsToHideIds() As String = { "FirstName", "LastName" }
    Public Const GroupedListViewNodeIdSuffix As String = "_Grouped"
    Public Const GroupByColumnId As String = "Position"
    Private Shared targetType As Type = GetType(Employee)
    Public Overrides Sub UpdateNode(ByVal viewsNode As ModelNode)
        AddFewColumnsListViewNode(viewsNode)
        AddGroupedListViewNode(viewsNode)
    End Sub
    Public Shared Function GetDefaultListView(ByVal viewsNode As ModelNode) As IModelListView
        Return viewsNode.Application.BOModel.GetClass(targetType).DefaultListView
    End Function
    Private Function AddListViewNode(ByVal viewsNode As ModelNode, ByVal listViewId As String) _
    As IModelListView
        Dim listViewNode As IModelListView = _
        CType(viewsNode.AddNode(Of IModelListView)(listViewId), IModelListView)
        listViewNode.ModelClass = viewsNode.Application.BOModel.GetClass(targetType)
        Return listViewNode
    End Function
    Private Sub AddFewColumnsListViewNode(ByVal viewsNode As ModelNode)
        Dim nodeId As String = GetDefaultListView(viewsNode).Id & FewColumnsListViewNodeIdSuffix
        Dim fewColumnsListViewNode As IModelListView = AddListViewNode(viewsNode, nodeId)
        Dim columns As IModelColumns = CType(fewColumnsListViewNode.Columns, IModelColumns)
        For Each columnId As String In columnsToHideIds
            columns.GetNode(columnId).Index = -1
        Next columnId
    End Sub
    Private Sub AddGroupedListViewNode(ByVal viewsNode As ModelNode)
        Dim nodeId As String = GetDefaultListView(viewsNode).Id & GroupedListViewNodeIdSuffix
        Dim groupedListViewNode As IModelListView = AddListViewNode(viewsNode, nodeId)
        Dim columns As IModelColumns = CType(groupedListViewNode.Columns, IModelColumns)
        CType(columns.GetNode(GroupByColumnId), IModelColumn).GroupIndex = 1
    End Sub
End Class

You can place this class in a separate code file in the module project, or add it to the Module.cs (Module.vb) file. The implemented Generator Updater should be registered in the overridden ModuleBase.AddGeneratorUpdaters method in the following manner:

C#

using DevExpress.ExpressApp.Model.Core;
// ...
public sealed partial class CreateNodesInCodeModule : ModuleBase {
    // ...
    public override void AddGeneratorUpdaters(ModelNodesGeneratorUpdaters updaters) {
        base.AddGeneratorUpdaters(updaters);
        updaters.Add(new AddListViewNodesGeneratorUpdater());
    }
}

VB.NET

Imports DevExpress.ExpressApp.Model.Core
' ...
Public NotInheritable Partial Class CreateNodesInCodeModule
    Inherits ModuleBase
    ' ...
    Public Overrides Sub AddGeneratorUpdaters(ByVal updaters As ModelNodesGeneratorUpdaters)
        MyBase.AddGeneratorUpdaters(updaters)
        updaters.Add(New AddListViewNodesGeneratorUpdater())
    End Sub
End Class

After implementing and registering the Generator Updater, rebuild the solution and invoke the Model Editor. The new ListView nodes are illustrated below.

Note

Your custom nodes and properties are not marked in bold font in the Model Editor, because these changes are generated in code. You can check the Model.DesignedDiffs.xafml source to ensure that it contains no customizations related to the generated nodes.

Create View Variants

Let us implement View Variants for Employee List View to make List Views created in the previous section of this topic visible in the UI. Although the View Variants are typically designed in the Model editor, it is also possible to create View Variants in code, via the Generator Updater. The Generator Updater that generates View Variants using Views created by the AddListViewNodesGeneratorUpdater is illustrated in the snippet below. The View Variants module should be added before implementing this class (see Provide Several View Variants for End-Users).

C#

using DevExpress.ExpressApp.Model;
using DevExpress.ExpressApp.Model.Core;
using DevExpress.ExpressApp.Model.NodeGenerators;
using DevExpress.ExpressApp.ViewVariantsModule;
// ...
class AddViewVariantsGeneratorUpdater : ModelNodesGeneratorUpdater<ModelViewsNodesGenerator> {
    public override void UpdateNode(ModelNode viewsNode) {
        IModelView rootView = AddListViewNodesGeneratorUpdater.GetDefaultListView(viewsNode);
        IModelView fewColumnsListView = 
            (IModelView)viewsNode.GetNode(rootView.Id +
            AddListViewNodesGeneratorUpdater.FewColumnsListViewNodeIdSuffix);
        IModelView groupedListView =
            (IModelView)viewsNode.GetNode(rootView.Id +
            AddListViewNodesGeneratorUpdater.GroupedListViewNodeIdSuffix);
        AddVariant("Default", "Default", rootView, rootView, true);
        AddVariant("FewColumns", "Few Columns", rootView, fewColumnsListView, false);
        AddVariant("Grouped", "Grouped", rootView, groupedListView, false);
    }
    void AddVariant(string variantId, string caption, 
        IModelView rootView, IModelView variantView, bool isCurrent) {
        IModelVariants variants = ((IModelViewVariants)rootView).Variants;
        IModelVariant variant = variants.AddNode<IModelVariant>(variantId);
        variant.View = variantView;
        variant.Caption = caption;
        if (isCurrent) variants.Current = variant;
    }
}

VB.NET

Imports DevExpress.ExpressApp.Model
Imports DevExpress.ExpressApp.Model.Core
Imports DevExpress.ExpressApp.Model.NodeGenerators
Imports DevExpress.ExpressApp.ViewVariantsModule
' ...
Friend Class AddViewVariantsGeneratorUpdater
    Inherits ModelNodesGeneratorUpdater(Of ModelViewsNodesGenerator)
    Public Overrides Sub UpdateNode(ByVal viewsNode As ModelNode)
        Dim rootView As IModelView = AddListViewNodesGeneratorUpdater.GetDefaultListView(viewsNode)
        Dim fewColumnsListView As IModelView = _
        CType(viewsNode.GetNode(rootView.Id + _
        AddListViewNodesGeneratorUpdater.FewColumnsListViewNodeIdSuffix), IModelView)
        Dim groupedListView As IModelView = _
        CType(viewsNode.GetNode(rootView.Id + _
        AddListViewNodesGeneratorUpdater.GroupedListViewNodeIdSuffix), IModelView)
        AddVariant("Default", "Default", rootView, rootView, True)
        AddVariant("FewColumns", "Few Columns", rootView, fewColumnsListView, False)
        AddVariant("Grouped", "Grouped", rootView, groupedListView, False)
    End Sub
    Private Sub AddVariant(ByVal variantId As String, ByVal caption As String, _
    ByVal rootView As IModelView, ByVal variantView As IModelView, ByVal isCurrent As Boolean)
        Dim variants As IModelVariants = (CType(rootView, IModelViewVariants)).Variants
        Dim [variant] As IModelVariant = variants.AddNode(Of IModelVariant)(variantId)
        [variant].View = variantView
        [variant].Caption = caption
        If isCurrent Then
            variants.Current = [variant]
        End If
    End Sub
End Class

This Generator Updater should also be registered in the module’s AddGeneratorUpdaters method.

C#

public sealed partial class CreateNodesInCodeModule : ModuleBase {
    // ...
    public override void AddGeneratorUpdaters(ModelNodesGeneratorUpdaters updaters) {
        base.AddGeneratorUpdaters(updaters);
        updaters.Add(new AddListViewNodesGeneratorUpdater());
        updaters.Add(new AddViewVariantsGeneratorUpdater());
    }
}

VB.NET

Public NotInheritable Partial Class CreateNodesInCodeModule
    Inherits ModuleBase
    ' ...
    Public Overrides Sub AddGeneratorUpdaters(ByVal updaters As ModelNodesGeneratorUpdaters)
        MyBase.AddGeneratorUpdaters(updaters)
        updaters.Add(New AddListViewNodesGeneratorUpdater())
        updaters.Add(new AddViewVariantsGeneratorUpdater())
    End Sub
End Class

After implementing and registering the Generator Updater, rebuild the solution and invoke the Model Editor for the module project. The new Variant nodes are illustrated below.

Now you can test the implemented Views and View Variants at runtime.

• Windows Forms Application:

  

• ASP.NET Application:

  

You can use a similar approach to create Generator Updaters for built-in or custom Nodes Generators.