PowerShell Move-SPUser equivalent in C#?

Hi,

I want to write a small application in C# that does the same as the Move-SPUser operation in PowerShell. Is there a method in SharePoint API for C#?

PS. It seems I can't use the SPFarm.MigrateUserAccount method in this case (I've tried, but it only works on ONE of the Web Applications in the Farm - I have two, where the one in question runs on port 81).

Thanks!