I am trying to implement IComponent rather than derive from Component becuase I wish to turn a (non-component) base class into a component (.NET does not support multiple inheritance - if it did I could simply derive from Component and my base class). However I can't overcome the "The base class'<base class name>'cannot be designed" error when I double-click the component and launch the default component designer. Please, does anyone know how to do this?

The following code sample is my implementation so far (for sake of simplicity the example does not explicitly derive from a base class - it implicitly derives from System.Object).

Component1.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Linq;
using System.Text;

namespace Example
{
[System.ComponentModel.DesignerCategory("Component")]
public partial class Component1 : IComponent
{
private ISite m_Site;
private bool m_Disposed;

public Component1()
{
InitializeComponent();
}

public Component1(IContainer container)
{
container.Add(this);
InitializeComponent();
}

~Component1()
{
this.Dispose(false);
}

protected virtual void Dispose(bool disposing)
{
if (!this.m_Disposed)
{
if (disposing)
{
/* release managed resources */
if (components != null)
components.Dispose();
}

/* release native resource */

this.m_Disposed = true;

if (this.Disposed != null)
this.Disposed(this, EventArgs.Empty);
}
}

#region IComponent Members

public event EventHandler Disposed;

public ISite Site
{
get { return m_Site; }
set { m_Site = value; }
}

#endregion

#region IDisposable Members

public void Dispose()
{
this.Dispose(true);
GC.SuppressFinalize(this);
}

#endregion
}
}

Component1.Designer.cs

namespace Example

{
partial class Component1
{
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.IContainer components = null;

#region Component Designer generated code

/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
components = new System.ComponentModel.Container();
}

#endregion
}
}

Your code does not work for me. You have forgotten to add the System.ComponentModel.DesignerCategory("Component") attribute to the class, but even with it added it still causes the "The base class 'System.Object' cannot be designed" error.

Are you sure your example appears as a component (not a class) in the solution explorer? And VisualStudio launches the Component designer when you double click the file?

FYI: I'm using Visual Studio Team System 2008 SP1

Thanks.

The code produces the following error:

The designer could not be shown for this file because none of the classes within it can be designed. The designer inspected the following classes in the file: MyComponent --- The base class 'SomeBaseClass' cannot be designed. SomeBaseClass --- The base class 'System.Object' cannot be designed.

Indeed I am!

As stated in the original post "when I double-click the component [in the solution explorer] and launch the default component designer" the component cannot be designed. The only work-arround for this I have found isto derive from this component again - the default component designer then works fine.

In other words, the class implementing IComponent cannot be designed, but any derived class can be. Could this be a bug with Visual Studio?

Just so it's clear: I don't have problems placingthe component from the toolbox onto the design surface of another component. The problem is the other way round - I cannot open the designer of the component to place other components on its design surface.

Thanks in advance.