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Flexible Combo Box and Editing Control free download

    Flexible Combo Box allows using any Control In ComboBox or in EditingControl for DataGridView, in Windows Forms Controls (C#, VB)

    Why Do I Create a Flexible Combo Box and Editing Control?

    1. I need to extend the DataGridViewColumn without rewriting it each time.
    2. I need the flexibility combobox to accept any control as a dropdown.

    What Does The Flexible Combo Box and Editing Control Do and Why is it Useful?

    1. Build your own grid column or your own combo simply.
    2. Use any control in the data grid column dynamically during the run and design time.
    3. It comes with a control converter and a control editor to change the control type that you create at design time.
    4. Both control converter and the control editor use as TypeConverter and Editor attributes in developing new controls.

    What problem does Flexible Combo Box Solve?

    1. Our component has a control property that creates controls of different types of design time and stores the created control as a simple text value.
    2. Use the Value property name of the drop-down control or editing control to specify the witch property to used to get the control value, for example:
      Control Value Property Name
      NumericUpDown Text
      CheckedListBox CheckedItems
      TimeEdit Value
    3. When using a list or a collectionfor the Value property name; the library will convert the value to string that contains all items in the collection.

    Using the Flexible Combo Box

    1. Create a new form in the Windows application.
    2. Add reference to AnyControlComboColumn.
    3. Add a new DataGridView and add a new column and set its type to GridColumn.
    4. In the property window, go to EditingControl(Create New) a property and choose the control type from the dropdown list.
    5. From the toolbox, add to the form DropDownCombo.
    6. In the property window, go to DropDownButton property and expand it.
    7. Under DropDownButton, go to DropDownControl(Create New) property and choose the control type from the dropdown list.

    Demo Application

    The demo application contains DropDownCombo; from the dropdown control choose: CheckedListBox or DirList or FileList, and it contains a DataGridViewwith two columns – the first with NumericUpDown as an editing control and the second column with Mask Text Box as an edit control.

    About this Library

    The library contains the following classes:

    1. DropDownButton: This class provides a dropdown button that accepts any control as a dropdown control and any other control to be the display area.
    2. DropDownCombo is a text box that contains the above dropdown button and so it provides a text box with dropdown control; you can set or change then control at run time or at design time.
    3. ControlConverter and ControlEditor provide a technique to serialize any control to simple text,  and we store text in the form designer.
    4. EditingControl, GridCell and GridColumn provide the ability to use any control as an editing control in DataGridView.

    About C# Code in This Article

    I develop this library using VB. I get the C# code using code converters. For more information about code converters, please see:

    About the DropDown Button

    1. The dropdown button is the major class for creating dropdown combos.
    2. If we add it to any control, I will dock it to the right side.
    3. It assigns two controls: the first is the dropdown control, and the second is the display area.
    4. The display area in the control will show the value of the created combo and could be a text box or rich text box or any control
    5. The dropdown control is the control that will be dropped when the dropdown button is clicked.
    6. To set up the dropdown control, you can choose control in the form or choose from a list that will contain all control types in system.windows.forms Assembly and assemblies that the application includes as a reference to them.
    7. When clicking the dropdown button, it will change the dropdown value to meet the value of the display area
    8. When the dropdown pop-up is closed, it will change the display area value to meet the value of the dropdown control
    9. DropDownCombo is a Text box that contains a dropdown button.

    About the GridColumn

    1. GridColumn is the class, which is used to extend the DataGridView to accept any control as editing control.
    2. To use this class, I need to use DataGridView, and add GridColum to it from DataGridView the Designer window.
    3. To set up the editing control, you can choose control in the form or choose from a list that will contain all control types of system.windows.forms Assembly and assemblies that the application includes a reference to them.

    About Control Converter and Control Properties Serialization

    Before building the control property for the dropdown control, you need to serialize it to string to be stored in the form designer, but don’t use XmlSerializer to serialize control properties because:

    1. XmlSerializer not supported types:
      • ISite
      • IDictionary
      • Any class that Implements unsupported interface
      • Any class has the property that returns an unsupported interface
      • Control
      • PropertyDescriptorCollection
      • SortedList
      • Collection
      • TreeNodeCollection
      • TreeNode
      • Any class that Inherits not supported class
      • Any class has the property that returns unsupported class
    2. Also, XmlSerializer can serialize the following types, but it can’t de-serialize them:
      • ArrayList
      • List of Objects
      • ListBox.ObjectCollection
      • CheckedListBox.ObjectCollection
    3. XmlSerializer returns a multi-line value, and it is better to store the control property as simple text
    4. To test XmlSerializer, you can use the following code:
    Imports System.Xml.Serialization
    Imports System.Reflection
    Imports System.ComponentModel
    Imports AnyControlComboColumn
    Imports System.Windows.Forms
    Public Module Module1
        Public Function Serialize(ByVal Value As Object) As String
                If Value Is Nothing Then
                    Return ""
                    Exit Function
                End If
                Dim Serializer As New XmlSerializer(Value.GetType)
                Dim vMemoryStream As New IO.MemoryStream
                Serializer.Serialize(vMemoryStream, Value)
                Dim s = System.Text.Encoding.UTF8.GetString(vMemoryStream.ToArray)
                s = s.Replace("<?xml version=""1.0""?>", _
    		"<?xml version=""1.0"" encoding=""utf-8""?>")
                vMemoryStream = New IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(s))
                s = System.Text.Encoding.UTF8.GetString(vMemoryStream.ToArray)
                'Try to Deserialize
                    Dim f = Serializer.Deserialize(vMemoryStream)
                Catch ex As Exception
                    Return ""
                End Try
                Return s
            Catch ex As Exception
                Return ""
            End Try
        End Function
    End Module
    using System;
    using System.Collections;
    using System.Collections.Generic;
    using System.Diagnostics;
    using System.Xml.Serialization;
    using System.Reflection;
    using System.ComponentModel;
    using AnyControlComboColumn;
    using System.Windows.Forms;
    namespace AnyControlComboColumn {
        public static class MSerialize {
            public static string Serialize(object Value) {
                try {
                    if (Value == null) {
                        return "";
                        return null;
                    XmlSerializer Serializer = new XmlSerializer(Value.GetType());
                    System.IO.MemoryStream vMemoryStream = new System.IO.MemoryStream();
                    Serializer.Serialize(vMemoryStream, Value);
                    var s = System.Text.Encoding.UTF8.GetString(vMemoryStream.ToArray());
                    s = s.Replace("<?xml version=\"1.0\"?>", "<?xml version=\"1.0\" encoding=\"utf-8\"?>");
                    vMemoryStream = new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(s));
                    s = System.Text.Encoding.UTF8.GetString(vMemoryStream.ToArray());
                    //>Try to Deserialize
                    try {
                        var f = Serializer.Deserialize(vMemoryStream);
                    } catch (Exception ex) {
                        return "";
                    return s;
                } catch (Exception ex) {
                    return "";

    We don’t use the default ComponentConverter because:

    1. It only allows selecting from pre-created controls in the form.
    2. It does not allow you to choose a control that is not present in the form.
    3. We can use it at design time only but not at runtime.

    What ComponentConverter does:

    1. Creates an instance of the control from the selected type.
    2. Convert the control to string stored in ControlText.
    3. Converts the control text to the control object.

    Points of Interest

    To assign a dropdown control to the dropdown button, we use the following properties:

    'Don't add TypeConverter attribute so this property use the default ComponentConverter
    <DisplayName("DropDownControl(Created in the form)")> _
    Public Property DropDownControl() As Control
    <TypeConverter(GetType(ControlConverter)), _
    Editor(GetType(ControlEditor), GetType(UITypeEditor)), _
    DisplayName("DropDownControl(Create New)")> _
    Public Property NewDropDownControl() As Control
    <Description("a text that will be used to create new DropDownControl")> _
    Public Overridable Property ControlText As String
    //dont put DesignerSerializationVisibility(DesignerSerializationVisibility.Content
    //this is only good for readonly property
    //ControlConverter does not work automatically if property type inherits form componenet or control
    //so we need a ControlText property
    [TypeConverter(typeof(ControlConverter)), Editor(typeof(ControlEditor), typeof(UITypeEditor)), 
    Description("Create new control displayed when OpenDropDown."), 
    DefaultValue(typeof(Control), "Nothing"), Category("DropDown"), 
    DisplayName("DropDownControl(Create New)"), EditorBrowsable(EditorBrowsableState.Advanced)]
    public Control NewDropDownControl { 
    [DefaultValue(""), Browsable(false), 
            Description("a text that will be used to create new DropDownControl")]
    public virtual string ControlText {
    //Don't add TypeConverter attribute so this property use the default ComponentConverter
    [Description("The control displayed when OpenDropDown."), 
    DefaultValue(typeof(Control), "Nothing"), Category("DropDown"), 
    DisplayName("DropDownControl(Select form the form controls)")]
    public Control DropDownControl {
    1. The DropDownControl property is named in the property windows as DropDownControl (created in the form) uses the default ComponentConverter to choose the control from already created control that is present in the parent form
    2. NewDropDownControl property is named in the property window as DropDownControl (create new) uses our control converter and control editor to select a control from a list containing all supported controls for applications or we can type the control name directly such as TextBox, Button and so on.
    3. ControlText property is a simple text property that accepts and returns a text that includes the control type name followed by the assembly name and the control none default properties values.

    The control converter uses the following code to convert the text to control:

     Public Overrides Function ConvertFrom(ByVal context As ITypeDescriptorContext, _
     ByVal culture As System.Globalization.CultureInfo, ByVal value As Object) As Object
            If value Is Nothing OrElse (Not TypeOf value Is String) _
            OrElse String.IsNullOrEmpty(CType(value, String)) Then
                Return Nothing
                Exit Function
            End If
            Dim vPropertyValues As New Dictionary(Of String, String)
            Dim TypeParts = Split(CType(value, String), "@")
            If UBound(TypeParts) <> 2 Then
                ReDim Preserve TypeParts(2)
            End If
            If String.IsNullOrEmpty(TypeParts(1)) Then
                TypeParts(1) = WinFormsAssemblyName
            End If
            vPropertyValues.Add(c_TypeName, TypeParts(0))
            vPropertyValues.Add(c_AssemblyName, TypeParts(1))
            Dim aPropertyValues() As String = Split(TypeParts(2), ",")
               For i As Integer = 0 To UBound(aPropertyValues)
                  If (Not String.IsNullOrEmpty(aPropertyValues(i))) AndAlso _
                    aPropertyValues(i).Contains(":"c) Then
                    Dim KeyAndValue = Split(aPropertyValues(i), ":")
                    vPropertyValues.Add(KeyAndValue(0).Trim, KeyAndValue(1).Trim)
                End If
            Return Me.CreateInstance(Nothing, vPropertyValues)
        Catch ex As Exception
            Return Nothing
        End Try
    End Function
    public override object ConvertFrom(ITypeDescriptorContext context, 
                    System.Globalization.CultureInfo culture, object value) {
        try {
            if (value == null || (! (value is string)) || string.IsNullOrEmpty(Convert.ToString(value))) {
                return null;
                return null;
            Dictionary<string,> vPropertyValues = new Dictionary<string,>();
            string[] TypeParts = Microsoft.VisualBasic.Strings.Split(Convert.ToString(value), 
                                     "@", -1, Microsoft.VisualBasic.CompareMethod.Binary);
            if (TypeParts.GetUpperBound(0) != 2)
                Array.Resize(ref TypeParts, 3);
            if (string.IsNullOrEmpty(TypeParts[1]))
                TypeParts[1] = WinFormsAssemblyName;
            vPropertyValues.Add(c_TypeName, TypeParts[0]);
            vPropertyValues.Add(c_AssemblyName, TypeParts[1]);
            string[] aPropertyValues = Microsoft.VisualBasic.Strings.Split(TypeParts[2], 
                                        ",", -1, Microsoft.VisualBasic.CompareMethod.Binary);
            for (int i = 0; i <= aPropertyValues.GetUpperBound(0); i++) {
                if ((! (string.IsNullOrEmpty(aPropertyValues[i]))) && aPropertyValues[i].Contains(":")) {
                    string[] KeyAndValue = Microsoft.VisualBasic.Strings.Split(aPropertyValues[i], ":", 
                                                 -1, Microsoft.VisualBasic.CompareMethod.Binary);
                    vPropertyValues.Add(KeyAndValue[0].Trim(), KeyAndValue[1].Trim());
            return CreateInstance(null, vPropertyValues);
        } catch (Exception ex) {
            return null;
    1. The Text format is TypeName@AssmblyName@ControlPropertyValues.
    2. First, the converter gets the type name and the assembly name properties values.
    3. It creates a properties values dictionary that comprises a pair of properties names and their values converted to string using the property assigned type converter and the assembly and type names.
    4. Create an instance of the control using CreateInstance method.
    5. To create an instance of the object from the type object, we use the following code:
      Public Overloads Shared Function CreateInstance(ByVal vType As Type) As Control
                  '####### Dim c As New vType is not correct
                  If vType Is Nothing Then
                      Return Nothing
                      Exit Function
                  End If
                  Dim ConstructorInfo = vType.GetConstructor({})
                  If ConstructorInfo Is Nothing Then
                      Return Nothing
                      Exit Function
                  End If
                  Return CType(ConstructorInfo.Invoke({}), Control)
              Catch ex As Exception
                  Return Nothing
              End Try
          End Function
      public static Control CreateInstance(Type vType) {
          try {
              //> Dim c As New vType is not correct
              if (vType == null) {
                  return null;
                  return null;
              var ConstructorInfo = vType.GetConstructor(new System.Type[0]);
              if (ConstructorInfo == null) {
                  return null;
                  return null;
              return (Control)(ConstructorInfo.Invoke(new System.Type[0]));
          } catch (Exception ex) {
              return null;
    6. To get the type object from the type name, we use the following code:
      Dim vAssembly = System.Reflection.Assembly.Load(AssemblyName)
      Dim vType = vAssembly.GetType(TypeName)
      var vAssembly = System.Reflection.Assembly.Load(AssemblyName);
      var vType = vAssembly.GetType(TypeName);

    To view the dropdown control, I use ToolStripDropDown and ToolStripControlHost:

    Private WithEvents Popup As ToolStripDropDown
    Private Host As ToolStripControlHost
    Public Property DropDownControl() As Control
            Return _DropDownControl
        End Get
        Set(ByVal value As Control)
               '....some code for testing and preparing value the cloning it to
                NewControl = ControlConverter.Clone(value)
                Host = Nothing
                _DropDownControl = NewControl
                _DropDownControl.Margin = Padding.Empty
                _DropDownControl.Padding = Padding.Empty
                Host = New ToolStripControlHost(_DropDownControl)
                Host.Margin = Padding.Empty
                Host.Padding = Padding.Empty
                Host.AutoSize = False
                Host.Size = value.Size
                Popup.Size = Host.Size
                Popup.AutoSize = True
                _DropDownControl.Location = New Point(0, 0)
                If _DisplayArea IsNot Nothing Then
                    DisplayAreaValue = DropDownControlValue
                End If
                OnClosed(Nothing, Nothing)
            Catch ex As Exception
            End Try
        End Set
    End Property
    Protected Overrides Sub OnClick(ByVal e As EventArgs)
            If Me.DroppedDown Then
                Me.OpenDropDown() 'Using Popup.Show method
            End If
        Catch ex As Exception
        End Try
    End Sub
    Public Overridable Sub OpenDropDown()
            If _DropDownControl Is Nothing OrElse Host Is Nothing OrElse _
            _DisplayArea Is Nothing Then Exit Sub
            Dim frm = _DisplayArea.FindForm
            Dim Pos As Point
            'additional code to adjust the position according to Drop Down Direction
            Pos = New Point(_DisplayArea.Left, _DisplayArea.Bottom + 1)
            Popup.Show(frm, Pos, ToolStripDropDownDirection.BelowRight)
        Catch ex As Exception
        End Try
    End Sub


    • Initial version