最近工作中需要把之前为VS 2010写的扩展迁移到VS 2012上。在将工程版本改为VS2012之后，代码没有修改，直接编译通过，也可以安装到VS2012上。
不过，在实际使用的时候，却报错，提示“The framework has not been sited!”。调试后发现，这个错误是我们在IDE开发中用到的VSXtra报出的。错误的报错位置是在SiteManager的GetGlobalService方法中：
// --------------------------------------------------------------------------------------------
/// <summary>
/// Gets a global service with the specified address and behavior type.
/// </summary>
/// <typeparam name="SInterface">Address type of the service</typeparam>
/// <typeparam name="TInterface">Behavior (endpoint) type of the service</typeparam>
/// <returns>The service instance obtained.</returns>
// --------------------------------------------------------------------------------------------
public static TInterface GetGlobalService<SInterface, TInterface>()
where TInterface : class
where SInterface : class
{
if (!HasGlobalServiceProvider)
throw new InvalidOperationException("The framework has not been sited!");
var ti = GlobalServiceProvider.GetService<SInterface, TInterface>();
if (ti == null)
throw new NotSupportedException(typeof(SInterface).FullName);
return ti;
}
从代码可以看到，异常抛出的条件是在GlobalServiceProvider不存在的时候。那么这个HasGlobalServiceProvider属性是什么样的呢：
// --------------------------------------------------------------------------------------------
/// <summary>
/// Gets the flag indicating if the SiteManager has already a global service provider or not.
/// </summary>
// --------------------------------------------------------------------------------------------
public static bool HasGlobalServiceProvider
{
get { return (GlobalServiceProvider != null); }
}
看来是判断GlobalServiceProvider是否为null。那么，是谁负责设置这个GlobalServiceProvider的呢？我们通过Find All References可以发现这个属性是在SuggestGlobalServiceProvider方法中被设置的，这个方法有多个重载，跟踪一下，需要调用到的是这个：
// --------------------------------------------------------------------------------------------
/// <summary>
/// Suggests a DTE2 object as the global service provider for SiteManager.
/// </summary>
/// <param name="dte2">DTE2 object as a global service provider candidate.</param>
// --------------------------------------------------------------------------------------------
public static void SuggestGlobalServiceProvider(DTE2 dte2)
{
SuggestGlobalServiceProvider(dte2 as IOleServiceProvider);
}
而这个SuggestGlobalServiceProvider则是在一个叫做TryToGetServiceProviderFromCurrentProcess的关键方法中被调用到的（部分代码省略）：
private static void TryToGetServiceProviderFromCurrentProcess(string vsMoniker)
{
...... string ideMoniker = String.Format(vsMoniker, Process.GetCurrentProcess().Id); ......
while (enumMoniker.Next(, moniker, IntPtr.Zero) == )
{
string displayName;
moniker[].GetDisplayName(ctx, moniker[], out displayName);
if (displayName == ideMoniker)
{
// --- Got the IDE Automation Object
Object oDTE;
rot.GetObject(moniker[], out oDTE);
dte = oDTE as DTE2;
if (dte != null) break;
}
} SuggestGlobalServiceProvider(dte);
}
其大概意思是从当前进程中获取一些信息，跟通过传入的vsMoniker格式化之后的一个字符串进行比对，如果名字是一样的，则通过它获取VS IDE的DTE实例。那么，这个vsMoniker是个什么东东？又是谁调用了这个方法呢？
// --------------------------------------------------------------------------------------------
/// <summary>
/// Monikers of possible DTE objects. Right now VS 2008 and VS 2010 is handled.
/// </summary>
// --------------------------------------------------------------------------------------------
private static readonly List<string> VSMonikers =
new List<string>
{
"!VisualStudio.DTE.9.0:{0}",
"!VisualStudio.DTE.10.0:{0}"
}; // --------------------------------------------------------------------------------------------
/// <summary>
/// The static constructor automatically tries to assign the SiteManager static class to a site
/// that accesses VS IDE global services.
/// </summary>
// --------------------------------------------------------------------------------------------
static SiteManager()
{
foreach (string moniker in VSMonikers)
{
TryToGetServiceProviderFromCurrentProcess(moniker);
if (HasGlobalServiceProvider) return;
}
}
看到这儿，我们也明白了，敢情VSXtra这儿写死了几个字符串{ "!VisualStudio.DTE.9.0:{0}", "!VisualStudio.DTE.10.0:{0}" }，跟VS版本相关，而VS2012的版本号是11，这里没有，所以当然找不到DTE Instance了。
最简单的修改版本，添加一个VS2012的版本号："!VisualStudio.DTE.11.0:{0}"，运行测试OK。
不过，对于这种hard-code的写法笔者是看着很不爽，那么，有没动态获取已经安装的VS版本的方法呢？答案是：有，通过注册表。
于是最后的代码修改如下：
// --------------------------------------------------------------------------------------------
/// <summary>
/// Monikers of possible DTE objects. Right now VS 2008 and VS 2010 is handled.
/// </summary>
// --------------------------------------------------------------------------------------------
private static readonly IEnumerable<string> VSMonikers; // --------------------------------------------------------------------------------------------
/// <summary>
/// The static constructor automatically tries to assign the SiteManager static class to a site
/// that accesses VS IDE global services.
/// </summary>
// --------------------------------------------------------------------------------------------
static SiteManager()
{
var vsRegKey = Registry.CurrentUser
.OpenSubKey("Software")
.OpenSubKey("Microsoft")
.OpenSubKey("VisualStudio");
var installedNames = vsRegKey.GetSubKeyNames().Where(x => !x.Contains("Exp") && !x.Contains("_Config"));
VSMonikers = installedNames.Select(x => "!VisualStudio.DTE." + x + ":{0}").ToArray(); foreach (string moniker in VSMonikers)
{
TryToGetServiceProviderFromCurrentProcess(moniker);
if (HasGlobalServiceProvider) return;
}
}