SqlCommand slow when executing a query with parameters - asp.net

Question

DbDataAdapter.Fill() is extremly slow when performing parameters!
I have a query with 2 parameters inside, and when I put those parameters hardcoded in the query it takes 1 second to execute (in a 470k table rows, returning only 20 rows).
I found many posts similars here and I tried all those solutions (set arithabort, option recompile, option optimize for, ...) with no luck.
I just perform a query (sql server 2008) and not a stored procedure, so the query with arithabort is like this:
string strSql = #"set ARITHABORT ON;
select TOP 20 ....
Also I tried to call set arithabort in the same transaction but performing that query first..
I don't know if I'm doing something wrong, but the sensation is the ado.net is performing a very bad execution plan in ado.net when I have defined parameters on it.
As a result of this bad choice, the execution time in SSMS is 1 second (after being cached) but in asp is like 9 seconds!
The query is something like this:
strSQL #="
select *
from Table1
where Name like #name";
And then:
DbProviderFactory factory = DbProviderFactories.GetFactory(mProvider);
DbCommand dbcmd = factory.CreateCommand();
if (CommandTimeout != null)
dbcmd.CommandTimeout = CommandTimeout.Value;
if(this.transaccion != null)
dbcmd.Transaction = this.transaccion;
dbcmd.Connection = dbc;
dbcmd.CommandText = strSQL;
if (parametros != null)
dbcmd.Parameters.AddRange(parametros);
DbDataAdapter dbda = factory.CreateDataAdapter();
dbda.SelectCommand = dbcmd;
DataTable dt = new DataTable();
dbda.Fill(dt);
return dt;
EDIT 14/01/2013 (18:44)
I'm not longer retrieve the connection from DbProviderFactory, insted I'm using directly SqlConnection and SqlCommand. I know DbCommand and DbProvider are a base clase... but I think there is something more in there.. because the performance drasticaly increase like 300%!
It's not the fill method, because I already tried in the code shown before..
Anyway, I don't know the reason why but using a SqlConnection is much faster! Any idea? Maybe isn't making that bad execution plan made before?
SqlCommand objCmd = new SqlCommand(strSQL, sqlConn);
if (CommandTimeout != null)
objCmd.CommandTimeout = CommandTimeout.Value;
if (this.transaccion != null)
objCmd.Transaction = SQLtransaccion;
if (parametros != null)
objCmd.Parameters.AddRange(parametros);
DbDataReader dbReader = objCmd.ExecuteReader();
DataTable dt = new DataTable();
dt.Load(dbReader);
dbReader.Close();
return dt;
Any help will be greatly appreciated,
Thanks,

Answer 1

I found the solution!
It was parameters!
I was using a wrong type in the the List!
Parametross.Add(bd.MakeParameter("#val", "%" + txtFind.Text + "%",
DbType.String));
DbType.String vs. DbType.AnsiString
Although both DbType.String and DbType.AnsiString deal with character data, these datatypes are processed differently, and using the wrong data type can have a negative effect on the application’s performance. DbType.String identifies the parameter as a 2-byte Unicode value and is sent to the server as such.DbType.AnsiString causes the parameter to be sent as a multibyte character string. To avoid excessive string conversions, use:
DbType.AnsiString for char or varchar columns and parameters.
DbType.String for unichar and univarchar columns and parameters.
Source:
http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.infocenter.dc20066.0115/html/adonet/adonet49.htm
In my query there is a:
....
where Table.Col1 like #val
But the column type was varchar and I should use DbType.AnsiString, instead of DbType.String
Parametross.Add(bd.MakeParameter("#val", "%" + txtFind.Text + "%",
DbType.AnsiString));
In my huge table I was making a lot of unnecesary casts and this is the reason why the performance drastically fall down!
Hope this will help someone,