request a Help

SqlConnection con =newSqlConnection();

SqlCommand com =newSqlCommand();

con.ConnectionString =

"Data Source=MADI-HP;Initial Catalog=Ba;Persist Security Info=True;User ID=sa;password=vahid_madi1359";

com.Connection = con;

con.Open();

string strSql1;

/*strSql1 ="SELECT count(*) FROM UsertaTable WHERE Username='+txt_username.Text+' and pass='+txt_password.Text+'";*/

strSql1 =

"SELECT[Username],[Pass] FROM [Herasat].[dbo].[UsertaTable] WHERE Username='+txt_username.Text+' and pass='+txt_password.Text+'";

SqlCommand mycmd=newSqlCommand();

mycmd.Connection = con;

mycmd.CommandText = strCon;

SqlDataAdapter da =newSqlDataAdapter();

da.SelectCommand= mycmd;

DataTable dt =newDataTable();

da.Fill(ds,

"UsertaTable");It doesent work.