So you’ve grabbed the latest 2.0 beta of DataStax C# driver from NuGet. Now what? In this talk, Luke will walk you through some of the basics of the C# driver--how to bootstrap the driver and connect to a cluster, execute statements, and retrieve result sets. Wondering what the difference between a PreparedStatement and a SimpleStatement is? Not sure what the appropriate lifetime for a Cluster or a Session object is and whether you should reuse one (from multiple threads)? What about ADO.NET and LINQ support? We’ll cover this and more, so that you can get on with building applications on top of Cassandra and .NET.

1. Getting Started with DataStax C#
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.AddQuery(bound);
batchStatement.AddQuery(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 Paging in a Web Application
• Show page of records in UI and allow user to
navigate
• Automatic Paging – this is not the feature you are
looking for

31. Where To Go From Here

32. 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

33. 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; }
}

34. 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();
}

35. 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

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

37. What Next?
• Data Modeling, Data Modeling, Data Modeling
• Planet Cassandra (http://www.planetcassandra.org)
• Links to videos, drivers, documentation, tutorials, etc.
Follow me on Twitter for updates: @LukeTillman