As suggested me Breck, I'm starting this thread for this question.

That's my code:

using System;
using System.Data.Common;

namespace SA11BUG
{
    class Program
    {
        static void MainUsingFactories()
        {
            var factory = DbProviderFactories.GetFactory("iAnywhere.Data.SQLAnywhere");

using (var connection = factory.CreateConnection())
            {
                connection.ConnectionString = "dsn=SQL Anywhere 11";
                connection.Open();

using (var command = connection.CreateCommand())
                {
                    command.CommandText = "select ? + ? from DUMMY";
                    command.Parameters.Add(factory.CreateParameter());
                    command.Parameters.Add(factory.CreateParameter());

command.Parameters[0].Value = "SQL";
                    command.Parameters[1].Value = "Anywhere";

#region This code is optional with no behavior change
                    command.Parameters[0].DbType = System.Data.DbType.String;
                    command.Parameters[1].DbType = System.Data.DbType.String;
                    #endregion

var result = (string)command.ExecuteScalar();

Console.WriteLine(result);
                    Console.ReadLine();
                }
            }
        }

static void MainUsingSAClasses()
        {
            using (var connection = new SAConnection("SQL Anywhere 11"))
            {
                connection.Open();

using (var command = connection.CreateCommand())
                {
                    command.CommandText = "select ? + ? from DUMMY";
                    command.Parameters.Add(new SAParameter {Value = "SQL"});
                    command.Parameters.Add(new SAParameter { Value = "Anywhere" });

#region This code is "optional" with no behavior change
                    command.Parameters[0].DbType = System.Data.DbType.String;
                    command.Parameters[1].DbType = System.Data.DbType.String;
                    #endregion

var result = (string)command.ExecuteScalar();

Console.WriteLine(result);
                    Console.ReadLine();
                }
            }
        }
    }
}

And this is the exception:

iAnywhere.Data.SQLAnywhere.SAException was unhandled
  Message="Cannot convert 'SQLAnywhere' to a int"
  Source="SQL Anywhere .NET Data Provider"
  ErrorCode=-2147467259
  NativeError=-157
  StackTrace:
       at iAnywhere.Data.SQLAnywhere.SACommand._ExecuteReader(CommandBehavior commandBehavior, Boolean isExecuteScalar, Boolean isBeginExecuteReader)
       at iAnywhere.Data.SQLAnywhere.SACommand.ExecuteScalar()
       at SA11BUG.Program.Main() in C:\Users\zote\Documents\Visual Studio 2008\Projects\SA11BUG\Program.cs:line 26
       at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

I'm using C# 3.5 and SA 11.0.1.2355. It's a BUG, I'm I right?!

Here is request log (-zr all option):

0106 162140.600,<,1,CONNECT
=,C,1,UID=bludata
+4,>,1,CONNECT,1
+1,<,1,PREPARE,select db_property('charset'), connection_property('charset'), @@VERSION, connection_property( 'max_statement_count' )
=,>,1,PREPARE,65536
=,<,1,EXEC,65536
+1,P,1,[S]DUMMY<seq>
=,>,1,EXEC
=,<,1,DROP_STMT,65536
=,>,1,DROP_STMT
=,<,1,STATUS_CHANGE_CHAR_CHARSET
=,>,1
=,<,1,STATUS_CHANGE_NCHAR_CHARSET
=,>,1
+7,<,1,EXEC_IMM,SELECT 1
=,P,1,[S]DUMMY<seq>
=,>.,1
+8,<,1,PREPARE,SELECT CURRENT DATABASE, @@version
=,>,1,PREPARE,65537
=,<,1,DESC_OUT,65537
+1,>,1,DESC_OUT
=,<,1,DESC_IN,65537
=,>,1,DESC_IN
+2,<,1,OPEN,65537
=,P,1,[S]DUMMY<seq>
=,>,1,OPEN,65538
+10,<,1,DESCRIPTOR,65538
=,>,1
=,<,1,FETCH,65538,1,Rel,1
=,>,1
=,<,1,PREFETCH,65538
+15,W,1,100,Row not found
=,>,1
+5,<,1,USE_PREFETCH,65538
=,>,1
=,<,1,CLOSE_BY_NAME
=,P,1,[S]DUMMY<seq>
=,>,1
=,<,1,COMMIT
=,>.,1
+1,<,1,DROP_STMT,65537
=,>,1,DROP_STMT
=,<,1,PREPARE,SET TEMPORARY OPTION QUOTED_IDENTIFIER = ON
=,>,1,PREPARE,65539
=,<,1,DESC_OUT,65539
=,>,1,DESC_OUT
=,<,1,DESC_IN,65539
=,>,1,DESC_IN
=,<,1,EXEC,65539
=,>,1,EXEC
=,<,1,COMMIT
=,>.,1
+39,<,1,DROP_STMT,65539
=,>,1,DROP_STMT
=,<,1,PREPARE,select ? + ? from DUMMY
=,>,1,PREPARE,65540
=,<,1,DESC_OUT,65540
=,>,1,DESC_OUT
=,<,1,DESC_IN,65540
=,>,1,DESC_IN
+7,<,1,OPEN,65540
=,H,1,0,nvarchar,'SQL'  
=,H,1,1,nvarchar,'Anywhere'  
=,P,1,[S]DUMMY<seq>
=,>,1,OPEN,65541
=,<,1,DESCRIPTOR,65541
=,>,1
=,<,1,FETCH,65541,1,Rel,1
=,E,1,-157,Cannot convert 'SQLAnywhere' to a int
=,>,1
+10005,P,1,[S]DUMMY<seq>