Question

protected void Page_Load(object sender, EventArgs e)
{

            string StartDate = Date3.Text;
            string Enddate = Date4.Text;

    ds = objBLL.GetUser(ItemType, ItemStatus);
                            dt = ds.Tables[0];
                            if (StartDate != null)
                            {
                              Filter records from datatable dt in such a way that
                              ParticipationStartDate > startDate");
                            }
                            if (Enddate != null)
                            {
                              Filter records from datatable dt in such a way that
                               ParticipationEndDate  < EndDate
                            }
                            if(StartDate!=null && Enddate!= null)
                             {
                               i need to filter records from datatable such that 
                               ParticipationStartDate  > StartDate
                               and ParticipationEndDate  < EndDate
                             }



}
                            GridView1.DataSource = dt;  dt is the filtered datatable
                            GridView1.DataBind();
                    }

ParticipationStartDate,ParticipationEndDate is a column in the datatable.
startdate and enddate are textbox fields in the aspx.
So this is what I am trying to do.
If the startdate(date3.text) is not null, then datatable should give the records such that ParticipationStartDate > startdate
If the enddate(date4.text) is not null, then datatable should give the records such that ParticipationEndDate < enddate

Answer 1

You can use the DataTable.DefaultView capabilities to do filtering. Example:

 if (StartDate != null)
 {
    dt.DefaultView.RowFilter="ParticipationStartDate > '"+startDate+"'";

 }

Then:

 GridView1.DataSource = dt.DefaultView; //note that you bind to DefaultView, not Datatable
 GridView1.DataBind();

Sample output:

DataTable dt = new DataTable();
dt.Columns.Add("Name");
dt.Columns.Add("DirectoryName");
dt.Columns.Add("CreationTime");
for (int i = 0; i < 10; i++)
{
  DataRow r = dt.NewRow();

  r.ItemArray = new object[] { "Name "+i,"Directory "+i, new DateTime(2011,10,15,23,22,i,0)};
  dt.Rows.Add(r);
 } //populated DataTable with 10 rows. Creation Time artificially set 

 //set filter to creation time >= 2011/10/15 23h 22m 4sec
 dt.DefaultView.RowFilter = "CreationTime >= '" + new DateTime(2011, 10, 15, 23, 22, 4, 5) + "'";
 rpt.DataSource = dt.DefaultView;
 rpt.DataBind();

Produces only 6 records on the filtered datatable: