OracleParameter y Cláusula IN

Puede envolverlo en el método OracleCommandExtension:

public static class OracleCommandExtension
{
    public static OracleCommand AddParameterCollection<TValue>(this OracleCommand command, string name, OracleType type, IEnumerable<TValue> collection)
    {
        var oraParams = new List<OracleParameter>();
        var counter = 0;
        var collectionParams = new StringBuilder(":");
        foreach (var obj in collection)
        {
            var param = name + counter;
            collectionParams.Append(param);
            collectionParams.Append(", :");
            oraParams.Add(new OracleParameter(param, type) { Value = obj });
            counter++;
        }
        collectionParams.Remove(collectionParams.Length - 3, 3);
        command.CommandText = command.CommandText.Replace(":" + name, collectionParams.ToString());
        command.Parameters.AddRange(oraParams.ToArray());
        return command;
    }
}