How to insert NULL/empty string in encrypted column - Always Encrypted - sql-server

Question

I have encrypted existing data using the SQL Server 2016 always encrypt method, one of column we have is NULLABLE but while insert from screen its not accepting either NULL or empty String. how to make it work if encrypted column is not mandatory on screen?

Answer 1

The error that you are seeing is incorrect, please ensure that you are passing the parameter correctly. Here is some sample code on how to do so.
Schema:
CREATE TABLE [dbo].[SO](
[ssn] [nvarchar](9) COLLATE Latin1_General_BIN2 ENCRYPTED WITH (COLUMN_ENCRYPTION_KEY = [CEK_Auto1], ENCRYPTION_TYPE = Deterministic, ALGORITHM = 'AEAD_AES_256_CBC_HMAC_SHA_256') NULL
)
GO
CREATE PROCEDURE dbo.insertSP #ssn nvarchar(9)
AS
INSERT INTO [dbo].[SO] ([SSN]) VALUES (#SSN);
GO
C# code:
SqlConnectionStringBuilder strbldr = new SqlConnectionStringBuilder();
strbldr.DataSource = ".";
strbldr.InitialCatalog = #"exptdb";
strbldr.IntegratedSecurity = true;
strbldr.ColumnEncryptionSetting = SqlConnectionColumnEncryptionSetting.Enabled;
string ssn = "";
using (var conn = new SqlConnection(strbldr.ConnectionString))
using (var command = conn.CreateCommand()) {
command.CommandType = CommandType.StoredProcedure;
command.CommandText = #"dbo.insertSP";
SqlParameter paramSSN = command.CreateParameter();
paramSSN.ParameterName = "#ssn";
paramSSN.SqlDbType = SqlDbType.NVarChar;
paramSSN.Direction = ParameterDirection.Input;
paramSSN.Value = ssn;
paramSSN.Size = 9;
command.Parameters.Add(paramSSN);
conn.Open();
command.ExecuteNonQuery();
}
Note, that in the scenario mentioned above, if
string ssn = "";
then the query succeeds, however if
string ssn = null;
you should see a failure on execution
Additional information: Procedure or function 'insertSP' expects
parameter '#ssn', which was not supplied.
This failure will occur even when ssn column is plaintext
You can insert null value in the encrypted column as follows, since null values are not encrypted:
using (var conn = new SqlConnection(strbldr.ConnectionString))
using (var command = conn.CreateCommand()) {
command.CommandText = #"INSERT INTO [dbo].[SO] ([SSN]) VALUES (null)";
conn.Open();
command.ExecuteNonQuery();
}