date range query problem

Hello,

I create a Web form project,it have A and B table, A table have ID,start_date and an end_date columns, B table have ID and name columns,

and need input a start_date and an end_date text box.

If both two text box input date to search, I want it return a date range that

table data's start_date >= input start_date and

table data's end_date >= input end_date.

I use StringBuilder to create SQL string to search, and use Parametes to phrase variable

but it doesn't work.

here's the code:

--------

StringBuilder sbStringSql = new StringBuilder();

sbStringSql.Append("select A.ID,B.NAME,A.STARTDATE,A.ENDDATE FROM A,B");

sbStringSql.Append("WHERE 1=1 AND A.ID=B.ID");

//------------------this way doesn't work-------------------------------

sbStringSql.Append(" and ((to_char(A.STARTDATE,'yyyy-mm-dd')) >=:STARTDATE");

sbStringSql.Append(" and (to_char(A.ENDDATE,'yyyy-mm-dd')) <=:ENDDATE)");

if (strSTARTDATE != string.Empty)

{

da.SelectCommand.Parameters.Add(new OracleParameter("STARTDATE",strSTARTDATE));

}

if (strENDDATE != string.Empty)

{

da.SelectCommand.Parameters.Add(new OracleParameter("ENDDATE", strENDDATE));

}
//-----------------------------------------------

//--------this way can work----------------

sbStringSql.Append(" and ((to_char(A.STARTDATE,'yyyy-mm-dd')) >='" + strSTARTDATE + "'");

sbStringSql.Append(" and (to_char(A.ENDDATE,'yyyy-mm-dd')) <='" + strENDDATE + "')");
//--------------------------------------------

The other way, I use BETWEEN ,but:

----

sbStringSql.Append(" and ((to_char(A.STARTDATE,'yyyy-mm-dd')) between '" + strSTARTDATE + "' and '" + strENDDATE + "')");

----

or

----

sbStringSql.Append(" and ((to_char(A.STARTDATE,'yyyy-mm-dd')) between :STARTDATE and :ENDDATE)");

if (strSTARTDATE != string.Empty)

{

da.SelectCommand.Parameters.Add(new OracleParameter("STARTDATE",strSTARTDATE));

if (strENDDATE != string.Empty)

{

da.SelectCommand.Parameters.Add(new OracleParameter("ENDDATE", strENDDATE));

}

----

both these two way can't work.

But when I use the SQL string in both way with Oracle SQL developer to run query, both works.

What is the problem?