Support dynamic help address resolution

For current moment developer have to put url to help topic into ExcelFunction attribute. So, it is unable to change URL dynamically, therefore it is unable to select different urls for production and staging environments.

What is expected: instead of http address. put link to static method, which will resolve help page dynamically.

E.g. signature can be:

public static Url ResolveHelpPage(ExcelFunctionAttribute targetMethod)

[govert]

Using the Registration helper is a bit simpler that the above example shows.

using System.Linq;
using ExcelDna.Integration;
using ExcelDna.Registration;

namespace RegistrationHelpUpdate
{
    public class AddIn : IExcelAddIn
    {
        public void AutoOpen()
        {
            RegisterFunctions();
        }

        public void AutoClose()
        {
        }

        public void RegisterFunctions()
        {
            ExcelRegistration.GetExcelFunctions()
                             .Select(funcReg => UpdateHelpTopic(funcReg))
                             .RegisterFunctions(); 
        }

        public ExcelFunctionRegistration UpdateHelpTopic(ExcelFunctionRegistration funcReg)
        {
            funcReg.FunctionAttribute.HelpTopic = "http://www.bing.com";
            return funcReg;
        }
    }

    public class Functions
    {
        [ExcelFunction(HelpTopic ="http://www.google.com")]
        public static object SayHelloFromRegistrationTest()
        {
            return "Hello!!!";
        }
    }
}

[augustoproiete]

@imanushin This can be done with the Excel-DNA Registration Helper, a library that allows you to dynamically register your functions.

Install the package ExcelDna.Registration in your project, so you can have access to the custom registration classes.

In your .dna file, set the flag ExplicitRegistration to true to tell Excel-DNA that you’ll be doing the registrations of the functions yourself.

e.g.

<DnaLibrary Name="MyAddIn Add-In" RuntimeVersion="v4.0">
  <ExternalLibrary Path="MyAddIn.dll" ExplicitRegistration="true" (...) />
</DnaLibrary>

Declare your functions normally:

public static class MyFunctions
{
    [ExcelFunction]
    public static string Hello()
    {
        return "Hi";
    }

    [ExcelFunction]
    public static string Hello2()
    {
        return "Hi2";
    }
}

In your AutoOpen, register the functions, replacing the HelpTopic of each of the functions as you need.

e.g.

public class MyAddIn : IExcelAddIn
{
    public void AutoOpen()
    {
        RegisterFunctions();
    }

    public void AutoClose()
    {
    }

    private static void RegisterFunctions()
    {
        var registrationEntries =
            from assembly in ExcelIntegration.GetExportedAssemblies()
            from type in assembly.GetTypes()
            from methodInfo in type.GetMethods(BindingFlags.Public | BindingFlags.Static)
            where methodInfo.GetCustomAttribute<ExcelFunctionAttribute>() != null
            select new ExcelFunctionRegistration(methodInfo);

        var delList = new List<Delegate>();
        var attList = new List<object>();
        var argAttList = new List<List<object>>();

        foreach (var entry in registrationEntries)
        {
            try
            {
                var del = entry.FunctionLambda.Compile();
                var att = entry.FunctionAttribute;

                // ***************************************************************
                // Detect the environment where the add-in is running somehow
                // and dynamically set the HelpTopic.

                // For example, via an appSetting entry in the App.config file:

                var environment = ConfigurationManager.AppSettings["Environment"];
                att.HelpTopic = $"http://{environment}/help/{att.Name}";
                // ***************************************************************

                var argAtt = new List<object>(entry.ParameterRegistrations.Select(pr => pr.ArgumentAttribute));

                delList.Add(del);
                attList.Add(att);
                argAttList.Add(argAtt);
            }
            catch (Exception ex)
            {
                LogDisplay.WriteLine("Exception while registering method {0} - {1}", entry.FunctionAttribute.Name, ex.ToString());
            }
        }

        ExcelIntegration.RegisterDelegates(delList, attList, argAttList);
    }
}

Of course, the above is just to give an example… You can also allow the developer to set a HelpTopic template in the ExcelFunction attribute, and then replace parts of it…

e.g.

public static class MyFunctions
{
    [ExcelFunction(HelpTopic = "http://%environment%/help/%name%")]
    public static string Hello()
    {
        return "Hi";
    }
}

  // ...
                // ***************************************************************
                // Detect the environment where the add-in is running somehow
                // and dynamically set the HelpTopic.

                // For example, via an appSetting entry in the App.config file:

                var environment = ConfigurationManager.AppSettings["Environment"];
                att.HelpTopic = att.HelpTopic.Replace("%environment%", environment);
                att.HelpTopic = att.HelpTopic.Replace("%name%", att.Name);
                // ***************************************************************
  // ...