C# – How to check when an item in MemoryCache will expire

ccachingmemorycache

Is it possible to read the expiration time of an item in MemoryCache?

I'm using the .NET System.Runtime.Caching.MemoryCache to store my configuration information for 30 min before I reload it from the database. As part of a status page I would like to show how old a specific cache item is or when it will expire.

object config = LoadSomeStuffFromDatabase();
CacheItemPolicy cachePolicy = new CacheItemPolicy() { AbsoluteExpiration = DateTime.Now.AddMinutes(30) }; 
Cache.Add("MyConfigKey", config, cachePolicy);

// And now I want to do something like this :-)
DateTime dt = Cache.SomeMagicMethod("MyConfigKey");

Today I'm using a variable that is updated every time I reload the configuration. But it would be much nicer to read this information from the cache itself.

Best Answer

I believe that this has already been answered:

How to get expiry date for cached item?

If that isn't what you're looking for, consider the following:

The API doesn't support getting the policy back from the retrieval of the cached item. Since you can cache any object, you could cache the policy in conjunction with the object and do some time based comparisons when you need to later access the object.

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C# – How to remedy “The breakpoint will not currently be hit. No symbols have been loaded for this document.” warning

Start debugging, as soon as you've arrived at a breakpoint or used Debug > Break All, use Debug > Windows > Modules. You'll see a list of all the assemblies that are loaded into the process. Locate the one you want to get debug info for. Right-click it and select Symbol Load Information. You'll get a dialog that lists all the directories where it looked for the .pdb file for the assembly. Verify that list against the actual .pdb location. Make sure it doesn't find an old one.

In normal projects, the assembly and its .pdb file should always have been copied by the IDE into the same folder as your .exe, i.e. the bin\Debug folder of your project. Make sure you remove one from the GAC if you've been playing with it.

C# – How and when to use ‘async’ and ‘await’

When using async and await the compiler generates a state machine in the background.

Here's an example on which I hope I can explain some of the high-level details that are going on:

public async Task MyMethodAsync()
{
    Task<int> longRunningTask = LongRunningOperationAsync();
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    //and now we call await on the task 
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public async Task<int> LongRunningOperationAsync() // assume we return an int from this long running operation 
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OK, so what happens here:

Task<int> longRunningTask = LongRunningOperationAsync(); starts executing LongRunningOperation
Independent work is done on let's assume the Main Thread (Thread ID = 1) then await longRunningTask is reached.

Now, if the longRunningTask hasn't finished and it is still running, MyMethodAsync() will return to its calling method, thus the main thread doesn't get blocked. When the longRunningTask is done then a thread from the ThreadPool (can be any thread) will return to MyMethodAsync() in its previous context and continue execution (in this case printing the result to the console).

A second case would be that the longRunningTask has already finished its execution and the result is available. When reaching the await longRunningTask we already have the result so the code will continue executing on the very same thread. (in this case printing result to console). Of course this is not the case for the above example, where there's a Task.Delay(1000) involved.

Best Answer

Related Solutions

C# – How to remedy “The breakpoint will not currently be hit. No symbols have been loaded for this document.” warning

C# – How and when to use ‘async’ and ‘await’

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