How to Connect to Snowflake from C# (.NET)

Snowflake is a cloud data warehouse, so connecting from C# looks a bit different from a local PostgreSQL or SQL Server connection: there is no host or port in the usual sense, the "server" is an account identifier, and as of late 2025 you can no longer log in with a single-factor password from a driver. The connection code itself is plain ADO.NET; the work is in the account identifier and the auth.

There is one driver that matters: Snowflake.Data, the official .NET connector maintained by Snowflake. Current version is 5.7.0 (as of June 2026). It implements the ADO.NET interfaces (SnowflakeDbConnection, SnowflakeDbCommand, SnowflakeDbDataReader), so Dapper works on top of it. There is no Entity Framework Core provider from Snowflake, and there is no second serious community driver, so the choice is made for you.

dotnet add package Snowflake.Data

The account identifier

The first thing that trips people up is the account value. The recommended format is the organization-account name, myorg-myaccount, not the legacy account locator (xy12345.eu-central-1). You can find both in the Snowflake UI under Admin -> Accounts. The org-account form is the one to use in new code; the locator form still works but is being phased out and behaves differently across regions.

You do not put a region in the connection string when you use the org-account identifier. That is a common mistake carried over from the old locator format.

Authentication after the November 2025 password block

Snowflake began blocking single-factor password sign-ins for programmatic connections in November 2025. A bare password=... connection that worked in 2024 will now fail for human-owned accounts. For service connections the supported path is key-pair (JWT) authentication.

Generate an unencrypted PKCS#8 private key and the matching public key:

openssl genrsa 2048 | openssl pkcs8 -topk8 -inform PEM -out rsa_key.p8 -nocrypt
openssl rsa -in rsa_key.p8 -pubout -out rsa_key.pub

Register the public key on the Snowflake user (strip the header, footer, and newlines from rsa_key.pub):

ALTER USER my_service_user SET RSA_PUBLIC_KEY='MIIBIjANBgkqh...';

Then connect with authenticator=snowflake_jwt and point the driver at the private key file:

using Snowflake.Data.Client;
 
var connString =
    "account=myorg-myaccount;" +
    "user=my_service_user;" +
    "authenticator=snowflake_jwt;" +
    "private_key_file=/secure/path/rsa_key.p8;" +
    "db=ANALYTICS;schema=PUBLIC;warehouse=COMPUTE_WH;role=ANALYST";
 
await using var conn = new SnowflakeDbConnection(connString);
await conn.OpenAsync();

If the key is encrypted, add private_key_pwd=.... For interactive local development, authenticator=externalbrowser opens your SSO login in a browser instead, which avoids handling keys at all.

Why warehouse, db, schema, and role belong in the connection string

Snowflake will happily connect you without a warehouse and then fail the first query with No active warehouse selected in the current session. Likewise, omitting role leaves you on your default role, which may not see the objects you expect, producing confusing "object does not exist" errors that are really permission errors. Set all four (warehouse, db, schema, role) up front so the session is fully scoped before you run anything.

Running a query

Snowflake.Data implements DbDataReader, so the pattern is standard ADO.NET:

await using var cmd = conn.CreateCommand();
cmd.CommandText = "SELECT id, name FROM customers LIMIT 10";
 
await using var reader = await cmd.ExecuteReaderAsync();
while (await reader.ReadAsync())
{
    var id = reader.GetInt64(0);
    var name = reader.GetString(1);
    Console.WriteLine($"{id}: {name}");
}

One thing to watch: Snowflake returns unquoted identifiers in uppercase. A column you wrote as select name comes back as NAME when you read it by name (reader["NAME"]). Reading by ordinal, as above, sidesteps the issue entirely.

Parameters

The connector uses positional parameters with ? placeholders, and you must set the Snowflake type via SnowflakeDbParameter:

using Snowflake.Data.Core;
 
await using var cmd = conn.CreateCommand();
cmd.CommandText = "SELECT id, name FROM customers WHERE country = ? AND created_at > ?";
 
var p1 = (SnowflakeDbParameter)cmd.CreateParameter();
p1.ParameterName = "1";
p1.SFDataType = SFDataType.TEXT;
p1.Value = "CH";
cmd.Parameters.Add(p1);
 
var p2 = (SnowflakeDbParameter)cmd.CreateParameter();
p2.ParameterName = "2";
p2.SFDataType = SFDataType.TIMESTAMP_NTZ;
p2.Value = new DateTime(2026, 1, 1);
cmd.Parameters.Add(p2);
 
await using var reader = await cmd.ExecuteReaderAsync();

Setting SFDataType matters most when the value can be null, since the driver cannot infer the type from a null Value.

Dapper

Because the connector is a real ADO.NET provider, Dapper (2.1.79 as of June 2026) works without anything Snowflake-specific:

using Dapper;
 
var rows = await conn.QueryAsync<Customer>(
    "SELECT id, name FROM customers WHERE country = ?",
    new { country = "CH" });

Note that Dapper's named-parameter convenience maps onto Snowflake's positional ? placeholders, so parameter order is what counts, not the property name.

Sessions, not pools

Snowflake connections are sessions against a remote warehouse, and they are relatively heavy to establish. The connector supports connection pooling, which is on by default and keyed by connection string; reuse the same connection string so pooled sessions are actually reused. For long-lived services, CLIENT_SESSION_KEEP_ALIVE=true (set as a connection parameter) keeps a session from expiring during idle periods. Do not hold a single connection open across an entire app and share it between threads; let the pool hand out sessions per unit of work.

Errors you actually hit

Snowflake's compute is billed by warehouse runtime, so an idle warehouse left running from a forgotten connection costs money. Set AUTO_SUSPEND on the warehouse and let sessions close cleanly.

For exploring Snowflake data and shaping queries before you wire them into C#, Mako connects to Snowflake with AI-powered autocomplete. Try it free at mako.ai.