IComponentDiscoveryService Interface

Definition

Namespace:

System.ComponentModel.Design

Assembly:

System.ComponentModel.TypeConverter.dll

Enables enumeration of components at design time.

public interface class IComponentDiscoveryService

public interface IComponentDiscoveryService

type IComponentDiscoveryService = interface

Public Interface IComponentDiscoveryService

Derived

System.Drawing.Design.ToolboxService

Examples

The following code example demonstrates how to use IComponentDiscoveryService to find all the types that derive from the ScrollableControl type.

// This class defines the designer actions that appear on the control
// that is being designed.
internal class DemoActionList :
      System.ComponentModel.Design.DesignerActionList
{
    // Cache a reference to the designer host.
    private IDesignerHost host = null;

    // Cache a reference to the control.
    private DemoControl relatedControl = null;

    // Cache a reference to the designer.
    private DemoControlDesigner relatedDesigner = null;

    //The constructor associates the control 
    //with the designer action list.
    public DemoActionList(IComponent component)
        : base(component)
    {
        this.relatedControl = component as DemoControl;

        this.host =
            this.Component.Site.GetService(typeof(IDesignerHost))
            as IDesignerHost;

        IDesigner dcd = host.GetDesigner(this.Component);
        this.relatedDesigner = dcd as DemoControlDesigner;
    }

    // This method creates and populates the 
    // DesignerActionItemCollection which is used to 
    // display designer action items.
    public override DesignerActionItemCollection GetSortedActionItems()
    {
        DesignerActionItemCollection items =
            new DesignerActionItemCollection();

        // If the Timer component has not been created, show the
        // "Create Timer" DesignerAction item.
        //
        // If the Timer component exists, show the timer-related
        // options.

        if (this.relatedDesigner.createdTimer == null)
        {
            items.Add(new DesignerActionMethodItem(
                this,
                "CreateTimer",
                "Create Timer",
                true));
        }
        else
        {   
            items.Add(new DesignerActionMethodItem(
                this,
                "ShowEventHandlerCode",
                "Show Event Handler Code",
                true));

            items.Add(new DesignerActionMethodItem(
                this,
                "RemoveTimer",
                "Remove Timer",
                true));
        }

        items.Add(new DesignerActionMethodItem(
           this,
           "GetExtenderProviders",
           "Get Extender Providers",
           true));

        items.Add(new DesignerActionMethodItem(
          this,
          "GetDemoControlReferences",
          "Get DemoControl References",
          true));

        items.Add(new DesignerActionMethodItem(
          this,
          "GetPathOfAssembly",
          "Get Path of Executing Assembly",
          true));

        items.Add(new DesignerActionMethodItem(
          this,
          "GetComponentTypes",
          "Get ScrollableControl Types",
          true));

        items.Add(new DesignerActionMethodItem(
            this,
            "GetToolboxCategories",
            "Get Toolbox Categories",
            true));

        items.Add(new DesignerActionMethodItem(
            this,
            "SetBackColor",
            "Set Back Color",
            true));

        return items;
    }

    // This method creates a Timer component using the 
    // IDesignerHost.CreateComponent method. It also 
    // creates an event handler for the Timer component's
    // tick event.
    private void CreateTimer()
    {
        if (this.host != null)
        {
            if (this.relatedDesigner.createdTimer == null)
            {
                // Create and configure the Timer object.
                this.relatedDesigner.createdTimer =
                    this.host.CreateComponent(typeof(Timer)) as Timer;
                Timer t = this.relatedDesigner.createdTimer;
                t.Interval = 1000;
                t.Enabled = true;

                EventDescriptorCollection eventColl =
                    TypeDescriptor.GetEvents(t, new Attribute[0]);

                if (eventColl != null)
                {
                    EventDescriptor ed =
                        eventColl["Tick"] as EventDescriptor;
                    if (ed != null)
                    {
                        PropertyDescriptor epd =
                            this.relatedDesigner.eventBindingService.GetEventProperty(ed);

                        epd.SetValue(t, "timer_Tick");
                    }
                }

                this.relatedDesigner.actionUiService.Refresh(this.relatedControl);
            }
        }
    }

    // This method uses the IEventBindingService.ShowCode
    // method to start the Code Editor. It places the caret
    // in the timer_tick method created by the CreateTimer method.
    private void ShowEventHandlerCode()
    {
        Timer t = this.relatedDesigner.createdTimer;

        if (t != null)
        {
            EventDescriptorCollection eventColl =
                TypeDescriptor.GetEvents(t, new Attribute[0]);
            if (eventColl != null)
            {
                EventDescriptor ed =
                    eventColl["Tick"] as EventDescriptor;
                if (ed != null)
                {
                    this.relatedDesigner.eventBindingService.ShowCode(t, ed);
                }
            }
        }
    }

    // This method uses the IDesignerHost.DestroyComponent method
    // to remove the Timer component from the design environment.
    private void RemoveTimer()
    {
        if (this.host != null)
        {
            if (this.relatedDesigner.createdTimer != null)
            {
                this.host.DestroyComponent(
                    this.relatedDesigner.createdTimer);

                this.relatedDesigner.createdTimer = null;

                this.relatedDesigner.actionUiService.Refresh(
                    this.relatedControl);
            }
        }
    }

    // This method uses IExtenderListService.GetExtenderProviders
    // to enumerate all the extender providers and display them 
    // in a MessageBox.
    private void GetExtenderProviders()
    {
        if (this.relatedDesigner.listService != null)
        {
            StringBuilder sb = new StringBuilder();

            IExtenderProvider[] providers =
                this.relatedDesigner.listService.GetExtenderProviders();

            for (int i = 0; i < providers.Length; i++)
            {
                sb.Append(providers[i].ToString());
                sb.Append("\r\n");
            }

            MessageBox.Show(
                sb.ToString(), 
                "Extender Providers");
        }
    }

    // This method uses the IReferenceService.GetReferences method
    // to enumerate all the instances of DemoControl on the 
    // design surface.
    private void GetDemoControlReferences()
    {
        if (this.relatedDesigner.referenceService != null)
        {
            StringBuilder sb = new StringBuilder();

            object[] refs = this.relatedDesigner.referenceService.GetReferences(typeof(DemoControl));

            for (int i = 0; i < refs.Length; i++)
            {
                sb.Append(refs[i].ToString());
                sb.Append("\r\n");
            }

            MessageBox.Show(
                sb.ToString(), 
                "DemoControl References");
        }
    }

    // This method uses the ITypeResolutionService.GetPathOfAssembly
    // method to display the path of the executing assembly.
    private void GetPathOfAssembly()
    {
        if (this.relatedDesigner.typeResService != null)
        {
            System.Reflection.AssemblyName name =
                System.Reflection.Assembly.GetExecutingAssembly().GetName();

            MessageBox.Show(
                this.relatedDesigner.typeResService.GetPathOfAssembly(name),
                "Path of executing assembly");
        }
    }

    // This method uses the IComponentDiscoveryService.GetComponentTypes 
    // method to find all the types that derive from 
    // ScrollableControl.
    private void GetComponentTypes()
    {
        if (this.relatedDesigner.componentDiscoveryService != null)
        {
            ICollection components = this.relatedDesigner.componentDiscoveryService.GetComponentTypes(host, typeof(ScrollableControl));

            if (components != null)
            {
                if (components.Count > 0)
                {
                    StringBuilder sb = new StringBuilder();

                    IEnumerator e = components.GetEnumerator();

                    while (e.MoveNext())
                    {
                        sb.Append(e.Current.ToString());
                        sb.Append("\r\n");
                    }

                    MessageBox.Show(
                        sb.ToString(), 
                        "Controls derived from ScrollableControl");
                }
            }
        }
    }

    // This method uses the IToolboxService.CategoryNames
    // method to enumerate all the categories that appear
    // in the Toolbox.
    private void GetToolboxCategories()
    {
        if (this.relatedDesigner.toolboxService != null)
        {
            StringBuilder sb = new StringBuilder();

            CategoryNameCollection names = this.relatedDesigner.toolboxService.CategoryNames;

            foreach (string name in names)
            {
                sb.Append(name.ToString());
                sb.Append("\r\n");
            }

            MessageBox.Show(sb.ToString(), "Toolbox Categories");
        }
    }

    // This method sets the shadowed BackColor property on the 
    // designer. This is the value that is serialized by the 
    // design environment.
    private void SetBackColor()
    {
        ColorDialog d = new ColorDialog();
        if (d.ShowDialog() == DialogResult.OK)
        {
            this.relatedDesigner.BackColor = d.Color;
        }
    }
}

' This class defines the designer actions that appear on the control
' that is being designed.

Friend Class DemoActionList
    Inherits System.ComponentModel.Design.DesignerActionList
    ' Cache a reference to the designer host.
    Private host As IDesignerHost = Nothing

    ' Cache a reference to the control.
    Private relatedControl As DemoControl = Nothing

    ' Cache a reference to the designer.
    Private relatedDesigner As DemoControlDesigner = Nothing

    'The constructor associates the control 
    'with the designer action list.
    Public Sub New(ByVal component As IComponent)
        MyBase.New(component)
        Me.relatedControl = component '

        Me.host = Me.Component.Site.GetService(GetType(IDesignerHost))

        Dim dcd As IDesigner = host.GetDesigner(Me.Component)
        Me.relatedDesigner = dcd

    End Sub

    ' This method creates and populates the 
    ' DesignerActionItemCollection which is used to 
    ' display designer action items.
    Public Overrides Function GetSortedActionItems() As DesignerActionItemCollection
        Dim items As New DesignerActionItemCollection()

        ' If the Timer component has not been created, show the
        ' "Create Timer" DesignerAction item.
        '
        ' If the Timer component exists, show the timer-related
        ' options.
        If Me.relatedDesigner.createdTimer Is Nothing Then
            items.Add(New DesignerActionMethodItem(Me, "CreateTimer", "Create Timer", True))
        Else
            items.Add(New DesignerActionMethodItem(Me, "ShowEventHandlerCode", "Show Event Handler Code", True))

            items.Add(New DesignerActionMethodItem(Me, "RemoveTimer", "Remove Timer", True))
        End If

        items.Add(New DesignerActionMethodItem(Me, "GetExtenderProviders", "Get Extender Providers", True))

        items.Add(New DesignerActionMethodItem(Me, "GetDemoControlReferences", "Get DemoControl References", True))

        items.Add(New DesignerActionMethodItem(Me, "GetPathOfAssembly", "Get Path of Executing Assembly", True))

        items.Add(New DesignerActionMethodItem(Me, "GetComponentTypes", "Get ScrollableControl Types", True))

        items.Add(New DesignerActionMethodItem(Me, "GetToolboxCategories", "Get Toolbox Categories", True))

        items.Add(New DesignerActionMethodItem(Me, "SetBackColor", "Set Back Color", True))

        Return items
    End Function

    ' This method creates a Timer component using the 
    ' IDesignerHost.CreateComponent method. It also 
    ' creates an event handler for the Timer component's
    ' tick event.
    Private Sub CreateTimer()
        If (Me.host IsNot Nothing) Then
            If Me.relatedDesigner.createdTimer Is Nothing Then
                ' Create and configure the Timer object.
                Me.relatedDesigner.createdTimer = Me.host.CreateComponent(GetType(Timer))

                Dim t As Timer = Me.relatedDesigner.createdTimer
                t.Interval = 1000
                t.Enabled = True

                Dim eventColl As EventDescriptorCollection = TypeDescriptor.GetEvents(t, New Attribute(-1) {})

                If (eventColl IsNot Nothing) Then
                    Dim ed As EventDescriptor = eventColl("Tick")

                    If (ed IsNot Nothing) Then
                        Dim epd As PropertyDescriptor = Me.relatedDesigner.eventBindingService.GetEventProperty(ed)

                        epd.SetValue(t, "timer_Tick")
                    End If
                End If

                Me.relatedDesigner.actionUiService.Refresh(Me.relatedControl)
            End If
        End If
    End Sub

    ' This method uses the IEventBindingService.ShowCode
    ' method to start the Code Editor. It places the caret
    ' in the timer_tick method created by the CreateTimer method.
    Private Sub ShowEventHandlerCode()
        Dim t As Timer = Me.relatedDesigner.createdTimer

        If (t IsNot Nothing) Then
            Dim eventColl As EventDescriptorCollection = TypeDescriptor.GetEvents(t, New Attribute(-1) {})
            If (eventColl IsNot Nothing) Then
                Dim ed As EventDescriptor = eventColl("Tick")

                If (ed IsNot Nothing) Then
                    Me.relatedDesigner.eventBindingService.ShowCode(t, ed)
                End If
            End If
        End If
    End Sub

    ' This method uses the IDesignerHost.DestroyComponent method
    ' to remove the Timer component from the design environment.
    Private Sub RemoveTimer()
        If (Me.host IsNot Nothing) Then
            If (Me.relatedDesigner.createdTimer IsNot Nothing) Then
                Me.host.DestroyComponent(Me.relatedDesigner.createdTimer)

                Me.relatedDesigner.createdTimer = Nothing

                Me.relatedDesigner.actionUiService.Refresh(Me.relatedControl)
            End If
        End If
    End Sub

    ' This method uses IExtenderListService.GetExtenderProviders
    ' to enumerate all the extender providers and display them 
    ' in a MessageBox.
    Private Sub GetExtenderProviders()
        If (Me.relatedDesigner.listService IsNot Nothing) Then
            Dim sb As New StringBuilder()

            Dim providers As IExtenderProvider() = Me.relatedDesigner.listService.GetExtenderProviders()

            Dim i As Integer
            For i = 0 To providers.Length - 1
                Dim o As Object = providers(i)
                sb.Append(o.ToString())
                sb.Append(ControlChars.Cr + ControlChars.Lf)
            Next i

            MessageBox.Show(sb.ToString(), "Extender Providers")
        End If
    End Sub

    ' This method uses the IReferenceService.GetReferences method
    ' to enumerate all the instances of DemoControl on the 
    ' design surface.
    Private Sub GetDemoControlReferences()
        If (Me.relatedDesigner.referenceService IsNot Nothing) Then
            Dim sb As New StringBuilder()

            Dim refs As Object() = Me.relatedDesigner.referenceService.GetReferences(GetType(DemoControl))

            Dim i As Integer
            For i = 0 To refs.Length - 1
                sb.Append(refs(i).ToString())
                sb.Append(ControlChars.Cr + ControlChars.Lf)
            Next i

            MessageBox.Show(sb.ToString(), "DemoControl References")
        End If
    End Sub

    ' This method uses the ITypeResolutionService.GetPathOfAssembly
    ' method to display the path of the executing assembly.
    Private Sub GetPathOfAssembly()
        If (Me.relatedDesigner.typeResService IsNot Nothing) Then
            Dim name As System.Reflection.AssemblyName = System.Reflection.Assembly.GetExecutingAssembly().GetName()

            MessageBox.Show(Me.relatedDesigner.typeResService.GetPathOfAssembly(name), "Path of executing assembly")
        End If
    End Sub


    ' This method uses the IComponentDiscoveryService.GetComponentTypes 
    ' method to find all the types that derive from 
    ' ScrollableControl.
    Private Sub GetComponentTypes()
        If (Me.relatedDesigner.componentDiscoveryService IsNot Nothing) Then
            Dim components As ICollection = Me.relatedDesigner.componentDiscoveryService.GetComponentTypes(host, GetType(ScrollableControl))

            If (components IsNot Nothing) Then
                If components.Count > 0 Then
                    Dim sb As New StringBuilder()

                    Dim e As IEnumerator = components.GetEnumerator()

                    While e.MoveNext()
                        sb.Append(e.Current.ToString())
                        sb.Append(ControlChars.Cr + ControlChars.Lf)
                    End While

                    MessageBox.Show(sb.ToString(), "Controls derived from ScrollableControl")
                End If
            End If
        End If
    End Sub


    ' This method uses the IToolboxService.CategoryNames
    ' method to enumerate all the categories that appear
    ' in the Toolbox.
    Private Sub GetToolboxCategories()
        If (Me.relatedDesigner.toolboxService IsNot Nothing) Then
            Dim sb As New StringBuilder()

            Dim names As CategoryNameCollection = Me.relatedDesigner.toolboxService.CategoryNames

            Dim name As String
            For Each name In names
                sb.Append(name.ToString())
                sb.Append(ControlChars.Cr + ControlChars.Lf)
            Next name

            MessageBox.Show(sb.ToString(), "Toolbox Categories")
        End If
    End Sub


    ' This method sets the shadowed BackColor property on the 
    ' designer. This is the value that is serialized by the 
    ' design environment.
    Private Sub SetBackColor()
        Dim d As New ColorDialog()
        If d.ShowDialog() = DialogResult.OK Then
            Me.relatedDesigner.BackColor = d.Color
        End If
    End Sub
End Class

Remarks

The default implementation of the IComponentDiscoveryService interface enables design-time enumeration of components in the Toolbox.

You could provide a custom implementation that enumerates across other types available at design time. For example, your implementation could enumerate the components that are present in a particular designer.

Methods

GetComponentTypes(IDesignerHost, Type)

Gets the list of available component types.

See also

• IDesignerHost
• IComponent