Since ReSharper only has a few macros that will make copies of other template variables, I started scouring the internet for clues and found this post. It’s a little outdate for ReSharper for 4.5, so here’s what I had to do to make my custom macro.

You can download the source or fork your own on GitHub.

Creating the Macro

1. Create a new C# class library project.
2. Add references to the following dlls:

   JetBrains.Platform.ReSharper.UI.dll
   JetBrains.ReSharper.Feature.Services.dll

3. Add a new class to your project and mark it with the Macro attribute and implement the IMacro interface:

   using System;
   using System.Collections.Generic;
   using System.Text.RegularExpressions;
   using JetBrains.ReSharper.Feature.Services.LiveTemplates.Macros;
   using JetBrains.ReSharper.Feature.Services.LiveTemplates.Hotspots;
   
   namespace ChrisLaco.ReSharper.Macros
   {
       // {#0:pattern}, etc are arguments that are passed to EvaluateQuickResult arguments[]
       [Macro("applyRegex", ShortDescription = "Replace string matching {#0:pattern} with {#1:string} in {#2:variable}", LongDescription = "Applies regex to replace value in another template variable.")]
       class ApplyRegexMacro : IMacro
       {
           #region IMacro Members
   
           public string EvaluateQuickResult(IHotspotContext context, IList<string> arguments)
           {
               if (arguments.Count != 3)
               {
                   return null;
               }
               else
               {
                   try
                   {
                       // Using the regex argument, replate the value of the specified template variable with the specified string
                       var result = Regex.Replace(arguments[2], arguments[0], arguments[1], RegexOptions.IgnoreCase);
   
                       return result;
                   }
                   catch (Exception e)
                   {
                       return "<" + e.Message + ">";
                   }
               }
           }
   
           public HotspotItems GetLookupItems(IHotspotContext context, IList<string> arguments)
           {
               return null;
           }
   
           public string GetPlaceholder()
           {
               return "a";
           }
   
           public bool HandleExpansion(IHotspotContext context, IList<string> arguments)
           {
               return false;
           }
   
           // Must return the same # of parameters declared in the Macro
           public ParameterInfo[] Parameters
           {
               get
               {
                   return new[] { new ParameterInfo(ParameterType.String), new ParameterInfo(ParameterType.String), new ParameterInfo(ParameterType.VariableReference) };
               }
           }
   
           #endregion
       }
   }

4. In AssemblyInfo.cs, apply assembly attributes for the ReSharper plugin manager:

   using System.Reflection;
   using System.Runtime.InteropServices;
   using JetBrains.UI.Application.PluginSupport;
   
   [assembly: PluginTitle("ChrisLaco.ReSharper.Macros")]
   [assembly: PluginDescription("Provides additional template macros: ApplyRegexMacro.")]
   [assembly: PluginVendor("Christopher H. Laco")]

   This information will be displayed in the ReSharper -> Plugins dialag:

   

5. To install plugin, simply copy the compiled dll into one of the follow directories:

   C:\Documents and Settings\username\Application Data\JetBrains\ReSharper\v4.5\vs9.0\Plugins
   C:\Program Files\JetBrains\ReSharper\v4.5\Bin\Plugins

Using the Macro

1. Select the macro from the list of available macros:
2. Click on the macro variables to set them:
3. Finish up the template text and savr your changes: