The check-and-set methods provide a mechanism for updating information only if the client knows the check (CAS) value. This can be used to prevent clients from updating values in the database that may have changed since the client obtained the value. Methods for storing and updating information support a CAS method that allows you to ensure that the client is updating the version of the data that the client retrieved.

The check value is in the form of a 64-bit integer which is updated every time the value is modified, even if the update of the value does not modify the binary data. Attempting to set or update a key/value pair where the CAS value does not match the value stored on the server will fail.

The behavior of Cas and ExecuteCas operations is defined by setting the first parameter to a value from the StoreMode enumeration.

The Cas() method is used to persist new values by key. Any class decorated with the Serializable attribute may be stored. The CAS value is returned by way of a CasResult

var casResult = client.Cas(StoreMode.Add, "beer", new Beer() {
    Brewer = "Thomas Hooker Brewing Company",
    Name = "American Ale"
});

if (casResult.Result)
{
    Console.WriteLine("Cas: ", casResult.Cas);
}

client.Cas(StoreMode.Set, "beer", new Beer() {
    Brewer = "Peak Organic Brewing Company",
    Name = "IPA"
}, TimeSpan.FromSeconds(60));

client.Cas(StoreMode.Replace, "beer", new Beer() {
    Brewer = "Six Point Craft Ales",
    Name = "Righteous Rye"
}, DateTime.Now.Addhours(1));

The ExecuteCas() methods are similar to the Cas methods, but return an instance of an IStoreOperationResult.

var result = client.ExecuteCas(StoreMode.Add, "beer", new Beer() {
    Brewer = "Thomas Hooker Brewing Company",
    Name = "American Ale"
});

if (! result.Success)
{
    Console.WriteLine("Store failed with message {0} and status code {1}", result.Message, result.StatusCode);
    
    if (result.Exception != null) 
    {
        throw result.Exception;
    }
}

client.ExecuteCas(StoreMode.Replace"beer", new Beer() {
    Brewer = "Thomas Hooker Brewing Co.",
    Name = "American Ale"
}, result.Cas);

client.ExecuteCas(StoreMode.Set, "beer", new Beer() {
    Brewer = "Peak Organic Brewing Company",
    Name = "IPA"
}, TimeSpan.FromSeconds(60));

client.ExecuteCas(StoreMode.Replace, "beer", new Beer() {
    Brewer = "Six Point Craft Ales",
    Name = "Righteous Rye"
}, DateTime.Now.Addhours(1));