DataStax-Examples/switch-connection-csharp

This application shows how to use the C# DataStax Driver to connect to an on-prem Cassandra database or a Astra database in the cloud at runtime using environment variables.Contributor(s): Dave BechbergerObjectivesShows the differences between a Cassandra connection configuration and an Astra connection configuration in a single app.Provide a demonstration of how to configure the database connection at runtime.See the documentation for more details about the Astra connection configuration for the C# DriverProject LayoutProgram.cs - The main application file which contains the logic to switch between the configurationsHow this Sample WorksThis sample uses environment variables to specify the configuration parameters and whether to use a Cassandra (DSE/DDAC/C*) configuration or an Astra configuration.All the logic to switch between the configurations occurs in the GetClientConfiguration method.If you specify the USEASTRA environment variable and it is true:The environment variables are checked to see that DBUSERNAME, DBPASSWORD, SECURECONNECTBUNDLEPATH, and KEYSPACE existIf they exist then the Astra connection is createdIf they do not exist then an error is thrownIf you so not specify the USEASTRA environment variable or it is false:The environment variables are checked to see that CONTACTPOINTS and DATACENTER existIf they exist then the standard connection is createdIf they do not exist then an error is thrownIf DBUSERNAME and DBPASSWORD exist then credentials are added to the configurationIf KEYSPACE exists then it is added to the configurationWhile these criteria added to the configuration are commonly used configuration parameters you are able to specify any additional ones in the code.Additionally while this example uses environment variables to control which configuration is selected this could also be done via the use of configuration files or command line parameters.For clarity this sample does not contain any of the normal error handling process you would want to wrap around connecting to a cluster to handle likely errors that would occur.Setup and RunningPrerequisites.NET Core 2.1A Cassandra cluster or an Astra database to connect to with the appropriate connection informationRunningTo connect to an Astra database you first need to download the secure connect bundle following the instructions found here.This first step in the process is to build the application. This can be done using the following command:dotnet buildOnce you have compiled the connection information and built the application you can run this to connect to Astra by using the command below, with the appropriate configuration added:USEASTRA=true DBUSERNAME=XXX DBPASSWORD=XXX KEYSPACE=XXX SECURECONNECTBUNDLEPATH="/valid/path/to/secureconnectbundle.zip" dotnet runIf you would like to connect to a Cassandra cluster use the command below, with the appropriate configuration added:CONTACTPOINTS=XX.XX.XX.XX dotnet runOnce you run this against either option you will get output that specifies the number of hosts and their IP addresses printed to the console:Connected to cluster with 3 host(s) XX.XX.XX.XX:9042,XX.XX.XX.XX:9042,XX.XX.XX.XX:9042