How to clear cacheKey in separate instance of IMemoryCache

问题

I'm running on ASP.NET Core 1.1 where in my Startup.cs I configure Policies, as well as DistributedMemoryCache, like this:

var roleRepo = new RoleRepo(Configuration, new MemoryCache(new MemoryCacheOptions()));

services.Configure<AuthorizationOptions>(options =>
{
    options.AddPolicy("MyPolicy", policy => policy.Requirements.Add(new MyPolicyRoleRequirement(roleRepo)));
});

services.AddDistributedMemoryCache();

//...

services.AddTransient<IRoleRepo, RoleRepo>();

The problem I'm having is I'm trying to remove a specific cacheKey for a specific user. When the user gets added to a new role, I then try to remove the existing cache entry for that cacheKey (username plus rolename), and then re-add with the updated "isInRole" value. But when my controller that removes, then adds the new cacheKey checks to see if the query exists, it always returns null. Then, if I try to navigate to the page that checks whether the user is in the role or not, that check still shows the PREVIOUS value of the cacheKey.

What I believe is going on is that since my policies get passed a single instance of my RoleRepo (which injects IMemoryCache), it ends up being a separate instance vs the one that is DI'd in the services.AddTransient line.

How do I configure this so either the IMemoryCache is a singleton, or specifically pass the SAME instance of my RoleRepo into the services.AddTransient line?

Here's my `RoleRepo setup:

private readonly IMemoryCache _memoryCache;

public RoleRepo(IConfigurationRoot configuration, IMemoryCache memoryCache)
    : base(configuration)
{
    _memoryCache = memoryCache;
}

回答1:

I found a solution to the issue. Since I'm "newing-up" my RoleRepo, I just went ahead and added THAT INSTANCE as a singleton...

services.AddSingleton<IRoleRepo>(roleRepo);

来源：https://stackoverflow.com/questions/58203771/how-to-clear-cachekey-in-separate-instance-of-imemorycache