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Build a C# App with CockroachDB and the .NET Npgsql Driver
Learn how to use CockroachDB from a simple C# (.NET) application with a low-level client driver.
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This tutorial shows you how build a simple C# application with CockroachDB and the .NET Npgsql driver.

We have tested the .NET Npgsql driver enough to claim beta-level support. If you encounter problems, please open an issue with details to help us make progress toward full support.

Before you begin

{% include {{page.version.version}}/app/before-you-begin.md %}

Step 1. Create a .NET project

{% include copy-clipboard.html %}

$ dotnet new console -o cockroachdb-test-app

{% include copy-clipboard.html %}

$ cd cockroachdb-test-app

The dotnet command creates a new app of type console. The -o parameter creates a directory named cockroachdb-test-app where your app will be stored and populates it with the required files. The cd cockroachdb-test-app command puts you into the newly created app directory.

Step 2. Install the Npgsql driver

Install the latest version of the Npgsql driver into the .NET project using the built-in nuget package manager:

{% include copy-clipboard.html %}

$ dotnet add package Npgsql

Step 3. Create the maxroach user and bank database

{% include {{page.version.version}}/app/create-maxroach-user-and-bank-database.md %}

Step 4. Generate a certificate for the maxroach user

Create a certificate and key for the maxroach user by running the following command. The code samples will run as this user.

{% include copy-clipboard.html %}

$ cockroach cert create-client maxroach --certs-dir=certs --ca-key=my-safe-directory/ca.key

Step 5. Convert the key file for use by C# programs

The private key generated for user maxroach by CockroachDB is PEM encoded. To read the key in a C# application, you will need to convert it into PKCS#12 format.

To convert the key to PKCS#12 format, run the following OpenSSL command on the maxroach user's key file in the directory where you stored your certificates:

{% include copy-clipboard.html %}

$ openssl pkcs12 -inkey client.maxroach.key -password pass: -in client.maxroach.crt -export -out client.maxroach.pfx

As of December 2018, you need to provide a password for this to work on macOS. See https://github.com/dotnet/corefx/issues/24225.

Step 6. Run the C# code

Now that you have created a database and set up encryption keys, in this section you will:

Basic example

Replace the contents of cockroachdb-test-app/Program.cs with the following code:

{% include copy-clipboard.html %}

{% include {{ page.version.version }}/app/basic-sample.cs %}

Then, run the code to connect as the maxroach user. This time, execute a batch of statements as an atomic transaction to transfer funds from one account to another, where all included statements are either committed or aborted:

{% include copy-clipboard.html %}

$ dotnet run

The output should be:

Initial balances:
	account 1: 1000
	account 2: 250

Transaction example (with retry logic)

Open cockroachdb-test-app/Program.cs again and replace the contents with the code shown below.

{% include {{page.version.version}}/client-transaction-retry.md %}

{% include copy-clipboard.html %}

{% include {{ page.version.version }}/app/txn-sample.cs %}

Then, run the code to connect as the maxroach user. This time, execute a batch of statements as an atomic transaction to transfer funds from one account to another, where all included statements are either committed or aborted:

{% include copy-clipboard.html %}

$ dotnet run

The output should be:

Initial balances:
	account 1: 1000
	account 2: 250
Final balances:
	account 1: 900
	account 2: 350

However, if you want to verify that funds were transferred from one account to another, use the built-in SQL client:

{% include copy-clipboard.html %}

$ cockroach sql --certs-dir=certs --database=bank -e 'SELECT id, balance FROM accounts'
  id | balance
+----+---------+
   1 |     900
   2 |     350
(2 rows)

Step 3. Create the maxroach user and bank database

{% include {{page.version.version}}/app/insecure/create-maxroach-user-and-bank-database.md %}

Step 4. Run the C# code

Now that you have created a database and set up encryption keys, in this section you will:

Basic example

Replace the contents of cockroachdb-test-app/Program.cs with the following code:

{% include copy-clipboard.html %}

{% include {{ page.version.version }}/app/insecure/basic-sample.cs %}

Then, run the code to connect as the maxroach user and execute some basic SQL statements: creating a table, inserting rows, and reading and printing the rows:

{% include copy-clipboard.html %}

$ dotnet run

The output should be:

Initial balances:
	account 1: 1000
	account 2: 250

Transaction example (with retry logic)

Open cockroachdb-test-app/Program.cs again and replace the contents with the code shown below.

{% include {{page.version.version}}/client-transaction-retry.md %}

{% include copy-clipboard.html %}

{% include {{ page.version.version }}/app/insecure/txn-sample.cs %}

Then, run the code to connect as the maxroach user. This time, execute a batch of statements as an atomic transaction to transfer funds from one account to another, where all included statements are either committed or aborted:

{% include copy-clipboard.html %}

$ dotnet run

The output should be:

Initial balances:
	account 1: 1000
	account 2: 250
Final balances:
	account 1: 900
	account 2: 350

However, if you want to verify that funds were transferred from one account to another, use the built-in SQL client:

{% include copy-clipboard.html %}

$ cockroach sql --insecure  --database=bank -e 'SELECT id, balance FROM accounts'
  id | balance
+----+---------+
   1 |     900
   2 |     350
(2 rows)

What's next?

Read more about using the .NET Npgsql driver.

{% include {{ page.version.version }}/app/see-also-links.md %}