Using NpgsqlParameter with empty value throws ArgumentNullException

[kbogun]

Steps to reproduce

using (NpgsqlConnection connection = new NpgsqlConnection("Host=localhost;Database=test;Username=test_user;Password=test_pass"))
using (NpgsqlCommand command = connection.CreateCommand())
{
   connection.Open();
   
   command.CommandText = "CALL procedureName(foo=>@p_foo)";

   NpgsqlParameter param = new NpgsqlParameter();
   param.ParameterName = "@p_foo";
   param.Value = "";
   command.Parameters.Add(param);

   command.ExecuteNonQuery();
}

The issue

Using NpgsqlParameter with empty value throws ArgumentNullException. In version 7.0.6 it works correctly.

Exception message: System.ArgumentNullException: 'Array cannot be null. Parameter name: chars'
Stack trace:
   at System.Text.UTF8Encoding.GetByteCount(Char* chars, Int32 count)
   at System.Text.EncodingExtensions.GetByteCount(Encoding encoding, ReadOnlySpan`1 chars)
   at Npgsql.Internal.Converters.StringBasedTextConverter`1.GetSize(SizeContext context, T value, Object& writeState)
   at Npgsql.Internal.PgConverter`1.GetSizeAsObject(SizeContext context, Object value, Object& writeState)
   at Npgsql.Internal.PgConverterExtensions.GetSizeOrDbNullAsObject(PgConverter converter, DataFormat format, Size writeRequirement, Object value, Object& writeState)
   at Npgsql.Internal.PgTypeInfo.BindObject(PgConverter converter, Object value, Size& size, Object& writeState, DataFormat& format, Nullable`1 formatPreference)
   at Npgsql.NpgsqlParameter.BindCore(Boolean allowNullReference)
   at Npgsql.NpgsqlParameter.Bind(DataFormat& format, Size& size)
   at Npgsql.NpgsqlParameterCollection.ProcessParameters(PgSerializerOptions options, Boolean validateValues, CommandType commandType)
   at Npgsql.NpgsqlCommand.<ExecuteReader>d__119.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Npgsql.NpgsqlCommand.<ExecuteReader>d__119.MoveNext()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlCommand.<ExecuteNonQuery>d__107.MoveNext()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlCommand.ExecuteNonQuery()

Further technical details

Npgsql version: 8.0.0
PostgreSQL version: 16.0
Operating system: Windows 10 22H2

[xxl-cc]

I encountered the same problem using nlog to write logs to the database, which was normal in 7.0.6.

[ebitencourt]

same problem using QueryOver
.Where(d => d.proc == null || d.proc == "")

[NinoFloris]

@kbogun thanks for your report.

I noticed in your stacktrace you're running on an older TFM for which we unfortunately don't have good CI coverage.

And indeed the cause of this issue is in the polyfills we're using on .NET Standard builds where we don't have System.Text.Encoding methods taking spans.

I've submitted a fix in #5453 which will be part of 8.0.1.