If you add a DateTimePicker to your application, you can set the MinDate and MaxDate properties to the limits you require. The user will not be able to select a date outside that range.
"i wants to textbox1->pick date like as 7\12\11
textbox2->pick date 1\4\12 after then we get record any emp between these days...
thanks.."
Don't use text boxes - use two DateTimePickers instead - that way the user gets to enter the date in his preferred format without any work from you (so if he is American his date will be set to MM/dd/yyyy and if he is European his date will be dd/MM/yyyy).
To retrieve records from a database just use the values:
SqlCommand cmd = new SqlCommand("SELECT * FROM myTable WHERE myDate BETWEEN @START AND @END", con);
cmd.Parameters.AddWithValue("@START", dtpStartDate.Value);
cmd.Parameters.AddWithValue("@END", dtpEndDate.Value);
...