Excel-DNA (http://excel-dna.net) sample showing how to load/unload other add-ins from a host add-in

AddInHost.dna

<DnaLibrary Name="AddInHost" Language="C#" RuntimeVersion="v4.0">
<Reference Name="System.Windows.Forms" />
<![CDATA[
using System;
using System.Windows.Forms;
using ExcelDna.Integration;

public class MyMacros
{

    public static object registerId;

    [ExcelCommand(MenuName="AddinHost", MenuText="Load Addin")]
    public static void LoadAddin()
    {
        XlCall.XlReturn result = XlCall.TryExcel(XlCall.xlfRegister, out registerId, @"C:\Work\ExcelDna\Samples\MetaAddin\AddIn.xll");
    }

    [ExcelCommand(MenuName="AddinHost", MenuText="Unload Addin")]
    public static void UnloadAddin()
    {
        MessageBox.Show("About to call xlAutoRemove.");
        
        string theName = @"C:\Work\ExcelDna\Samples\MetaAddin\AddIn.xll";
        object removeId = XlCall.Excel(XlCall.xlfRegister, theName, "xlAutoRemove", "I" , ExcelMissing.Value, ExcelMissing.Value, 2);
        object removeResult = XlCall.Excel(XlCall.xlfCall, removeId);	
        object removeUnregister = XlCall.Excel(XlCall.xlfUnregister, removeId);

        object success = XlCall.Excel(XlCall.xlfUnregister, registerId);
        MessageBox.Show("Result of Unregister: " + success.ToString() );
    }


}


public static class MyFunctions
{
    public static string AddinHostTestFunction()
    {
        return "Hello from the add-in host!";
    }
    
    
    [ExcelCommand(MenuName="AddinHost", MenuText="Say Hello!")]
    public static void AddIn()
    {
        MessageBox.Show("Hello from the add-in host!");
    }
}
]]>
</DnaLibrary>