in these date is not taking from database some other date is taking

string strqry = "select dob from master_studentpersonal where stud_id= '" +
                                                           TextBox1.Text + "'";
DataTable dt = mc.selectQryDataTable2(strqry);
DataView dv = new DataView(dt);
DateTime dob = new DateTime();
if (dob != null)
{
    if (dob <= new DateTime(2004, 01, 01) &&
        dob <= new DateTime(2005, 12, 31))
    {
        TextBox6.Text = "Group A";

    }
    else if (dob <= new DateTime(2003, 12, 31) &&am开发者_如何学编程p;
             dob <= new DateTime(2002, 01, 01))
    {
        TextBox6.Text = "Group B";
    }
}

plz help me friends

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You haven't assigned the value from your SQL query to your dob variable. dob is only ever set to the value that comes with an empty constructor. Also, as Chris F said, check the conditions for the two if statements: currently if the date is less than or equal to 31/12/2005 the group will always be A.

---

dob will never be null, both because you assign it and because DateTime is a value type. Doesn't fix your problem, but it'll tidy your code ;-)

More importantly though, you never assign a value to it, so it's going to pick up an arbitrary value like DateTime.MinValue (at a guess).

---

In addition to Dan Iveson's answer - your output will always be "Group A" because 2003-12-31 <= 2004-01-01.

I guess you meant:

string strqry = "select dob from master_studentpersonal where stud_id= '" + 
                                                           TextBox1.Text + "'"; 
DataTable dt = mc.selectQryDataTable2(strqry); 
DataView dv = new DataView(dt); 
DateTime dob = // get date of birth from dt
if (dob != null) 
{ 
    if (dob <= new DateTime(2003, 12, 31) && 
             dob >= new DateTime(2002, 01, 01)) 
    { 
        TextBox6.Text = "Group B"; 
    } 
    else if (dob >= new DateTime(2004, 01, 01) && 
        dob <= new DateTime(2005, 12, 31)) 
    { 
        TextBox6.Text = "Group A";  
    } 
} 

---

Your TextBox will say "Group A" everytime:

DateTime dob = new DateTime();
if (dob != null)    // dob can't be null unless you haven't instantiated it, 
                    // it's a value type. Actually it's 
                    // value here is always DateTime.MinValue, 
                    // since you aren't assigning anything to it.

{
    if (dob <= new DateTime(2004, 01, 01) &&
        dob <= new DateTime(2005, 12, 31))    // this second check is redundant.
                                              // if this condition is ever evaluated,
                                              // it will always be true. I assume you have
                                              // mixed up your < and > signs here  
    {
        TextBox6.Text = "Group A";

    }
    else if (dob <= new DateTime(2003, 12, 31) &&  // as above, this statement can never
                                                   // evaluate to true. you won't even
                                                   // reach this code unless dob > 2004
             dob <= new DateTime(2002, 01, 01))
    {
        TextBox6.Text = "Group B";
    }
}