how to compare date in gridview

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ASP.NET4

i am displayed date without using db...using this code

DataTable dt = new DataTable();
dt.Columns.AddRange(new DataColumn[1] { new DataColumn("Datess") });
ViewState["Customers"] = dt;
DateTime startDate = new DateTime(2015, 1, 26);
DateTime stopDate = new DateTime(2015, 2, 28);
int interval = 1;

for (DateTime dateTime = startDate; dateTime < stopDate; dateTime += TimeSpan.FromDays(interval))
{
dt.Rows.Add(startDate);
startDate = startDate.AddDays(interval);
ViewState["Customers"] = dt;
}
GridView1.DataSource = (DataTable)ViewState["Customers"];
GridView1.DataBind();

o/p is like this....

date
26/1/2015
..
....
27/2/2015

then i want to compare these date with my database table DATE
my database is

date       42 43 47 78
29/1/2015   p  p  A  P
2/2/2015    A  P  P   A

i want to compare these two date and display like this

date       42 43 47 78
26/1/2015
27/1/2015
28/1/2015
29/1/2015   p  p  A  P
30/1/2015
31/1/2015
2/2/2015    A  P   P   A
.....
...
27/2/2015