can't retrieve the wanted data out from database - asp.net

Question

I have created an ASP.NET application in Visual Studio 2010. I am having trouble in retrieving the data i wanted from the two dates i selected from the date picker. once i select the 2 dates, it just keep displaying all the data out and not the dates that i have selected.
This is my code:
protected void Page_Load(object sender, EventArgs e)
{
string startdate = (string)Session["startdate"];
string enddate = (string)Session["enddate"];
DateTime one = Convert.ToDateTime(startdate);
DateTime two = Convert.ToDateTime(enddate);
if (DateTime.Compare(two, one)>=0)
{
SqlConnection conn = new SqlConnection("Data Source=localhost;Initial Catalog=ncpsdbb;Integrated Security=True");
conn.Open();
SqlCommand sqlcmd = new SqlCommand("SELECT * FROM StudentTransactions WHERE TimeDate BETWEEN '" + startdate + "' AND '" + enddate + "')", conn);
SqlDataAdapter da = new SqlDataAdapter(sqlcmd);
DataSet ds = new DataSet();
da.Fill(ds);
GridView1.Visible = true;
GridView1.DataBind();
conn.Close();
}
else
{
GridView1.Visible = false;
string strMsg = " Data not found for the choosen dates.";
Response.Write("<script>alert('" + strMsg + "')</script>");
}
}

Answer 1

My initial observation is that there is a ) in your SQL with no matching ( - I wonder if your command is simply throwing an exception...?
The first thing I would try is parameterizing it; in addition to being a really really good idea anyway, it could avoid formatting (dd/MM vs MM/dd) issues in the dates:
if(two >= one)
{
DataSet ds = new DataSet();
using(var conn = new SqlConnection("Data Source=localhost;Initial Catalog=ncpsdbb;Integrated Security=True"))
using(var sqlcmd = new SqlCommand("SELECT * FROM StudentTransactions WHERE TimeDate BETWEEN #start AND #end", conn))
using(var da = new SqlDataAdapter(sqlcmd))
{
sqlcmd.Parameters.AddWithValue("start", one);
sqlcmd.Parameters.AddWithValue("end", two);
conn.Open();
da.Fill(ds);
}
}

Answer 2

using(SqlConnection conn = new SqlConnection("Data Source=localhost;Initial Catalog=ncpsdbb;Integrated Security=True"))
{
conn.Open();
SqlCommand sqlcmd = new SqlCommand("SELECT * FROM StudentTransactions WHERE TimeDate BETWEEN #startDate AND #endDate", conn);
sqlcmd.Parameters.AddWithValue("startDate" <Your start date>);
sqlcmd.Parameters.AddWithValue("endDate" <Your end date>);
...
Also notice the error with parantheses in your command string.