检测是否加载了HttpModule

public static bool IsHttpModuleLoaded(string moduleName)
{
    HttpApplication app = HttpContext.Current.ApplicationInstance;
    Type appType = app.GetType();
    FieldInfo pi = appType.GetField("_modules", BindingFlags.Instance | BindingFlags.NonPublic);
    if (pi == null)
        return false;
    IHttpModule[] modules = pi.GetValue(app) as IHttpModule[];
    if (modules == null)
        return false;
    foreach (IHttpModule module in modules)
    {
        if (module.GetType().Name == moduleName)
            return true;
    }
    return false;
}

bool isLoaded = IsHttpModuleLoaded("HttpModule");

HttpApplication app = HttpContext.Current.ApplicationInstance;
IHttpModule[] modules = app.Modules;
bool isLoaded = false;
foreach (IHttpModule module in modules)
{
    if (module.GetType().Name == "HttpModule")
    {
        isLoaded = true;
        break;
    }
}

 <modules>
    <add name="HttpModule" type="HttpModuleNamespace.HttpModule, HttpModuleAssembly" />
  </modules>
</system.webServer>

public static void AddHttpModule(string moduleName, string assemblyName)
{
    HttpApplication app = HttpContext.Current.ApplicationInstance;
    Type appType = app.GetType();
    FieldInfo pi = appType.GetField("_modules", BindingFlags.Instance | BindingFlags.NonPublic);
    if (pi == null)
        return;
    IHttpModule[] modules = pi.GetValue(app) as IHttpModule[];
    if (modules == null)
        return;
    foreach (IHttpModule module in modules)
    {
        if (module.GetType().Name == moduleName)
            return;
    }
    IHttpModule newModule = Activator.CreateInstance(assemblyName, moduleName).Unwrap() as IHttpModule;
    if (newModule == null)
        return;
    Array.Resize(ref modules, modules.Length + 1);
    modules[modules.Length - 1] = newModule;
    pi.SetValue(app, modules);
}

AddHttpModule("HttpModule", "HttpModuleAssembly");