Prepending in Memcached with C# (Detailed Guide w/ Code Examples)

Use Case(s)

Prepending in Memcached is commonly used when you want to add data at the beginning of an existing value stored in a Memcached key. This is often useful for things like log aggregation or building a string from parts where order matters.

Code Examples

Let's consider a simple example using the Enyim.Caching library. Here we will store a value against a key and then prepend data to it.

// Create the memcached client MemcachedClient client = new MemcachedClient(); // Store a value client.Store(StoreMode.Set, "key", "World"); // Prepend data client.Prepend("key", "Hello "); // Fetch the data var val = client.Get<string>("key"); Console.WriteLine(val); // Outputs: Hello World

In this example, we store the string 'World' against the key 'key'. We then prepend the string 'Hello ' to the stored value. When the value is fetched, it now contains 'Hello World'.

Best Practices

  • Ensuring atomicity: The prepend operation in Memcached is atomic. This means that you don't need to worry about race conditions between fetching the old value, modifying it, and storing it back.
  • Error Handling: Always handle potential connection errors when interacting with Memcached. This could be network issues, timeouts, etc.

Common Mistakes

  • Trying to prepend to non-string values: Memcached prepend operation only works on string values. If the original value is not a string, unexpected behavior can occur.
  • Ignoring return values: Memcached operations return a boolean indicating success or failure. Many developers ignore these, believing operations always succeed, leading to subtle bugs.


Q: Can I prepend to a value that doesn't exist? A: No, Memcached's prepend operation requires the key to already exist in the cache. If it doesn't, the prepend operation will fail.

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