1.在项目中添加基于Base Command等的类，可改变命名空间名称。

2.引用:命名空间.类名称；

实例：

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Resources;
using System.Reflection;

using System.Drawing;
using ESRI.ArcGIS.ADF.BaseClasses;
using ESRI.ArcGIS.ADF.CATIDs;
using ESRI.ArcGIS.Controls;
using ESRI.ArcGIS.Carto;
using ESRI.ArcGIS.Display;

namespace CSharpMyFullExtent
{
/// <summary>
/// Command that works in ArcMap/Map/PageLayout
/// </summary>
[Guid("4f4e73b1-40c3-44a5-8729-d403b7b3d779")]
[ClassInterface(ClassInterfaceType.None)]
[ProgId("CSharpMyFullExtent.MyFullExtentCommand")]
public sealed class MyFullExtentCommand : BaseCommand
{
#region COM Registration Function(s)
[ComRegisterFunction()]
[ComVisible(false)]
static void RegisterFunction(Type registerType)
{
// Required for ArcGIS Component Category Registrar support
ArcGISCategoryRegistration(registerType);

//
// TODO: Add any COM registration code here
//
}

[ComUnregisterFunction()]
[ComVisible(false)]
static void UnregisterFunction(Type registerType)
{
// Required for ArcGIS Component Category Registrar support
ArcGISCategoryUnregistration(registerType);

//
// TODO: Add any COM unregistration code here
//
}

#region ArcGIS Component Category Registrar generated code
/// <summary>
/// Required method for ArcGIS Component Category registration -
/// Do not modify the contents of this method with the code editor.
/// </summary>
private static void ArcGISCategoryRegistration(Type registerType)
{
string regKey = string.Format("HKEY_CLASSES_ROOT\\CLSID\\{{{0}}}", registerType.GUID);
MxCommands.Register(regKey);
ControlsCommands.Register(regKey);
}
/// <summary>
/// Required method for ArcGIS Component Category unregistration -
/// Do not modify the contents of this method with the code editor.
/// </summary>
private static void ArcGISCategoryUnregistration(Type registerType)
{
string regKey = string.Format("HKEY_CLASSES_ROOT\\CLSID\\{{{0}}}", registerType.GUID);
MxCommands.Unregister(regKey);
ControlsCommands.Unregister(regKey);
}

#endregion
#endregion

private IHookHelper m_hookHelper = null;
public MyFullExtentCommand()
{
//
// TODO: Define values for the public properties
//
base.m_category = "CustomCommands"; //localizable text
base.m_caption = "My Full Extent"; //localizable text
base.m_message = "My Full Extent"; //localizable text
base.m_toolTip = "My Full Extent"; //localizable text
base.m_name = "MyCommands_MyFullExtent"; //unique id, non-localizable (e.g. "MyCategory_MyCommand")

//As part of your deployment strategy you must register the name of the WinHelp file (*.hlp)
//as a new string value in: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Help
//or provide the full path name.
base.m_helpFile = "MyHelpFile.hlp";

//The Context Help ID as defined when compiling the RTF file into the HelpFile
base.m_helpID = 1234;

ResourceManager rm = new ResourceManager("CSharpMyFullExtent.Resources", Assembly.GetExecutingAssembly());
base.m_bitmap = (System.Drawing.Bitmap)rm.GetObject("CommandImage");
}

#region Overriden Class Methods

/// <summary>
/// Occurs when this command is created
/// </summary>
/// <param name="hook">Instance of the application</param>
public override void OnCreate(object hook)
{
if (hook == null)
return;

try
{
m_hookHelper = new HookHelperClass();
m_hookHelper.Hook = hook;
if (m_hookHelper.ActiveView == null)
m_hookHelper = null;
}
catch
{
m_hookHelper = null;
}

if (m_hookHelper == null)
base.m_enabled = false;
else
base.m_enabled = true;

}

/// <summary>
/// Occurs when this command is clicked
/// </summary>
public override void OnClick()
{
//Get IActiveView interface
IActiveView pActiveView = m_hookHelper.FocusMap as IActiveView;

//Set the extent to the full extent
pActiveView.Extent = pActiveView.FullExtent;

//Refresh the active view
pActiveView.Refresh();
}

#endregion
}
}

引用：

axToolbarControl1.AddItem("CSharpMyFullExtent.MyFullExtentCommand", 0, -1, true, 0, esriCommandStyles.esriCommandStyleIconOnly);