Create a TCP connection when using ADO.NET

Demonstrates opening a TCP connection to Cloud SQL for SQL Server using an ADO.NET Connection object.

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For detailed documentation that includes this code sample, see the following:

Code sample


To authenticate to Cloud SQL for SQL Server, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

using Microsoft.Data.SqlClient;
using System;

namespace CloudSql
    public class SqlServerTcp
        public static SqlConnectionStringBuilder NewSqlServerTCPConnectionString()
            // Equivalent connection string:
            // "User Id=<DB_USER>;Password=<DB_PASS>;Server=<INSTANCE_HOST>;Database=<DB_NAME>;"
            var connectionString = new SqlConnectionStringBuilder()
                // Note: Saving credentials in environment variables is convenient, but not
                // secure - consider a more secure solution such as
                // Cloud Secret Manager ( to help
                // keep secrets safe.
                DataSource = Environment.GetEnvironmentVariable("INSTANCE_HOST"), // e.g. ''
                // Set Host to 'cloudsql' when deploying to App Engine Flexible environment
                UserID = Environment.GetEnvironmentVariable("DB_USER"),         // e.g. 'my-db-user'
                Password = Environment.GetEnvironmentVariable("DB_PASS"),       // e.g. 'my-db-password'
                InitialCatalog = Environment.GetEnvironmentVariable("DB_NAME"), // e.g. 'my-database'

                // The Cloud SQL proxy provides encryption between the proxy and instance
                Encrypt = false,
            connectionString.Pooling = true;
            // Specify additional properties here.
            return connectionString;

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