Strings

For each Redis command (https://redis.io/commands), you should be able to find correspding API in our client StackExchange.Redis here: https://stackexchange.github.io/StackExchange.Redis/

For e.g. we will try to use the SETENX which will only set a value if it does not already exists in redis. Whenever using any command, ensure you check its complexity at https://redis.io/commands. For this case, complexity is O(1) which is the best you can have.

SET "test.key" "test.value" NX EX 900

In our ConsoleApp/Program.cs, lets add this method to check how to do this in Csharp

public static void SetStringIfNotAlreadyPresent(IDatabase db)
{
  // Delete key if it exists
  db.KeyDelete("my-key");

  // First time should set value
  db.StringSetAsync("my-key", "first value", null, When.NotExists);

  var result = db.StringGet("my-key");
  Console.WriteLine($"Value after first set: {result}");

  // Second time should not overwrite first value
  db.StringSetAsync("my-key", "second value", null, When.NotExists);
  var result2 = db.StringGet("my-key");
  Console.WriteLine($"Value after second set: {result2}");
}

On running the program, you should see folloing output :

Value after first set: first value Value after second set: first value

Now lets modify above command to add a TTL

public static void SetStringIfNotAlreadyPresentWithTTL(IDatabase db)
{
  // Delete key if it exists
  db.KeyDelete("my-key");

  // First time should set value
  db.StringSetAsync("my-key", "first value", TimeSpan.FromMilliseconds(100), When.NotExists);

  var result = db.StringGet("my-key");
  Console.WriteLine($"Value after first set: {result}");

  // Second time should not overwrite first value
  db.StringSetAsync("my-key", "second value", null, When.NotExists);
  Console.WriteLine($"Value after second set: {db.StringGet("my-key")}");

  Task.Delay(TimeSpan.FromMilliseconds(100)).GetAwaiter().GetResult();
  Console.WriteLine($"Value after TTL: {db.StringGet("my-key")}");

  // Third time should succeed as value is expired now
  db.StringSetAsync("my-key", "third value", null, When.NotExists);
  Console.WriteLine($"Value after third set: {db.StringGet("my-key")}");
}

On running the program, you should see folloing output :

Value after first set: first value Value after second set: first value Value after TTL: Value after third set: third value