1. Getting Started with DataStax .NET
Driver
Luke Tillman
Language Evangelist
@LukeTillman

2. Life as the .NET Language Evangelist

3. Where do I get the driver?
• NuGet
• GitHub
• https://github.com/datastax/csharp-driver

4. Bootstrapping the Driver

5. Cluster
• Singleton - one per application
• Use the Builder
Cluster cluster = Cluster.Builder()
.AddContactPoint("127.0.0.1")
.Build();

6. Cluster
• Fluent Interface with Lots of Options
var authProvider = new PlainTextAuthProvider("username", "password");
var queryOptions = new QueryOptions()
.SetConsistencyLevel(ConsistencyLevel.LocalQuorum)
.SetPageSize(1000);
Cluster cluster = Cluster.Builder().AddContactPoint("127.0.0.1")
.WithSSL()
.WithQueryOptions(queryOptions)
.WithAuthProvider(authProvider)
.Build();

7. Session
• Singleton per keyspace
• Inspired by the (N)Hibernate session object
• Get it from your Cluster object
ISession session = cluster.Connect("killrvideo");

8. Sample IoC Container Registration
// Use the Cluster builder to create a cluster
Cluster cluster = Cluster.Builder().AddContactPoint("127.0.0.1").Build();
// Use the cluster to connect a session to the appropriate keyspace
ISession session = cluster.Connect("killrvideo");
// Register both Cluster and ISession instances with Windsor (as
// Singletons since it will reuse the instance)
container.Register(
Component.For<Cluster>().Instance(cluster),
Component.For<ISession>().Instance(session)
);

9. Creating Statements

10. Types of Statements
• SimpleStatement
• PreparedStatement / BoundStatement
• BatchStatement

11. SimpleStatement
• It’s… simple?
• Can use bind parameters
• Useful for one-off statements or dynamic CQL where
you can’t prepare it
var statement =
new SimpleStatement("SELECT * FROM users WHERE userid = ?");
statement = statement.Bind(145);

12. PreparedStatement / BoundStatement
• Pay the cost of Prepare once (server roundtrip)
• Save the PreparedStatement instance and reuse
PreparedStatement prepared = session.Prepare(
"SELECT * FROM user_credentials WHERE email = ?");

13. PreparedStatement / BoundStatement
• Bind variable values to get BoundStatement for
execution
• Execution only has to send variable values
• You will use these all the time
BoundStatement bound =
prepared.Bind("luke.tillman@datastax.com");

14. BatchStatement
• Add Simple/Bound statements to a batch
BoundStatement bound = prepared.Bind(video.VideoId, video.Name);
var simple = new SimpleStatement(
"UPDATE videos SET name = ? WHERE videoid = ?"
).Bind(video.Name, video.VideoId);
// Use an atomic batch to send over all the mutations
var batchStatement = new BatchStatement();
batchStatement.Add(bound);
batchStatement.Add(simple);

15. BatchStatement
• Batches are Logged, atomic (by default) and this is
the most common use case
• Set the batch type to use a different type of batch
• Counters have their own batch type (can’t mix)
var batch =
new BatchStatement().SetBatchType(BatchType.Unlogged);

16. Statements – You’ve Got Options
• Simple and Bound statements have options that can
be set at the Statement level
• Consistency Level
• Retry Policy
• Paging Size (for automatic paging, we’ll come back to this)
• Tracing
• If not set at the statement level, defaults set when
configuring/building the Cluster are used

17. Statements – You’ve Got Options
• Example of binding a PreparedStatement and setting
available options:
IStatement bound =
prepared.Bind("luke.tillman@datastax.com")
.SetPageSize(100)
.SetConsistencyLevel(ConsistencyLevel.LocalOne)
.SetRetryPolicy(new DefaultRetryPolicy())
.EnableTracing();

18. Executing Statements and Getting the
Results

19. Executing Statements
• Use your Session object to execute statements
• You can execute statements synchronously or
asynchronously
• Synchronous
• Asynchronous
• Execute methods return a RowSet
RowSet rows = await _session.ExecuteAsync(boundStatement);
RowSet rows = _session.Execute(boundStatement);

20. RowSet
• RowSet implements IEnumerable<Row>
• Use GetValue<T> method on a Row to get a
column’s value
• By column name
• By ordinal (position)

21. RowSet
• Because RowSet implements IEnumerable<Row>:
• Iterate with foreach
RowSet rows = await _session.ExecuteAsync(boundStatement);
foreach (Row row in rows)
{
returnList.Add(new VideoPreview
{
VideoId = row.GetValue<Guid>("videoid"),
AddedDate = row.GetValue<DateTimeOffset>("added_date"),
Name = row.GetValue<string>("name")
});
}

22. RowSet
• Because RowSet implements IEnumerable<Row>:
• Project Rows with LINQ to Objects Select()
RowSet rows = await _session.ExecuteAsync(boundStatement);
var returnList = rows.Select(row => new VideoPreview
{
VideoId = row.GetValue<Guid>(0),
AddedDate = row.GetValue<DateTimeOffset>(1),
Name = row.GetValue<string>(2)
}).ToList();

23. RowSet
• Because RowSet implements IEnumerable<Row>:
• Get a single row with LINQ to Objects Single() or
SingleOrDefault()
RowSet rows = await _session.ExecuteAsync(boundStatement);
Row row = rows.SingleOrDefault();

24. CQL 3 Data Types to .NET Types
Full listing available in driver docs
CQL 3 Data Type .NET Type
bigint, counter long
boolean bool
decimal, float float
double double
int int
uuid, timeuuid System.Guid
text, varchar string (Encoding.UTF8)
timestamp System.DateTimeOffset
varint System.Numerics.BigIntege
r

25. Driver 2.0 Features

26. Lightweight Transactions (LWT)
• Use when you don’t want writes to step on each
other
• AKA Linearizable Consistency
• Serial Isolation Level
• Be sure to read the fine print: has a latency cost
associated with using it, so use only where needed
• The canonical example: unique user accounts

27. Lightweight Transactions (LWT)
• Returns a column called [applied] indicating
success/failure
• Different from the relational world where you might
expect an Exception (i.e.
var statement = new SimpleStatement("INSERT INTO user_credentials (email,
password) VALUES (?, ?) IF NOT EXISTS");
statement = statement.Bind("user1@killrvideo.com", "Password1!");
RowSet rows = await _session.ExecuteAsync(statement);
var userInserted = rows.Single().GetValue<bool>("[applied]");

28. Automatic Paging
• The Problem: Loading big result sets into memory is
a recipe for disaster (OutOfMemoryExceptions, etc.)
• Better to load and process a large result set in pages
(chunks)
• Doing this manually with Cassandra prior to 2.0 was
a pain

29. Automatic Paging
• Set a page size on a statement (or will use default from
Cluster)
• Iterate over the resulting RowSet
• As you iterate, new pages are fetched transparently when
the Rows in the current page are exhausted
• Will allow you to iterate until all pages are exhausted
boundStatement = boundStatement.SetPageSize(100);
RowSet rows = await _session.ExecuteAsync(boundStatement);
foreach (Row row in rows)
{
}

30. Typical Pager UI in a Web Application
• Show page of records in UI and allow user to
navigate

31. Typical Pager UI in a Web Application
• Automatic Paging – this is not the feature you are
looking for

32. Where To Go From Here

33. LINQ to CQL
• Comes in the NuGet package as
Cassandra.Data.Linq
• Has support for all CRUD operations
• Start by decorating the objects you’ll be querying
with Table, Column, and PartitionKey attributes

34. LINQ to CQL
[Table("user_credentials")]
public class UserCredentials
{
[Column("email")]
[PartitionKey]
public string EmailAddress { get; set; }
[Column("password")]
public string Password { get; set; }
[Column("userid")]
public Guid UserId { get; set; }
}

35. LINQ to CQL
• Then query with LINQ using the Session’s
GetTable<T> method as your starting point
public UserCredentials GetCredentials(string emailAddress)
{
IEnumerable<UserCredentials> results =
_session.GetTable<UserCredentials>()
.Where(uc => uc.EmailAddress == emailAddress)
.Execute();
return results.SingleOrDefault();
}

36. ADO.NET Support
• Available in the NuGet package as Cassandra.Data
• Allows you to use your “favorite” ADO.NET objects
like DbConnection, DbCommand, etc. to query
Cassandra
• My recommendation? Avoid it.
• Cassandra concepts don’t always map well to

37. The KillrVideo Sample Application
• Many of this presentation’s samples are taken from
here
• https://github.com/luketillman/killrvideo-csharp

38. What Next?
• Data Modeling, Data Modeling, Data Modeling
• Planet Cassandra (http://www.planetcassandra.org)
• Links to videos, drivers, documentation, tutorials, etc.
• 2.1 Beta Available (support for User Defined Types)
Follow me on Twitter for updates: @LukeTillman