C＃中的日期范围检查

Question

How to find if a date in the input is within a specific daterange (let's say for example wihtin last 7 days, meaning I will say -7). If it is within last 7 days, do something, else do something else.

I currently could do upto this, but I don't know how to change this further to meet what I want.

string a = "-1"; // These are values that are configurable based on which date is checked. Yesterday means, -1 for example. 
string b = "-15"; // -15 means within last 15 days.

DateTime d = input;
DateTime e = d.AddDays(int.Parse(a));
if (d is between datetime.now and e)
{
   //do something
} 
else do something

Answer 1

First of all, use meaningful names instead of a and b , secondly: use proper data types (you don't use b at all):

int dayOffset = -1;
int lowerBound = -15;

var currentDate = DateTime.Now;

if(input >= currentDate.AddDays(dayOffset) && input <= currentDate)
{ // do smoething }

Using your names:

var currentDate = DateTime.Now;

if(input >= currentDate.AddDays(a) && input <= currentDate)
{ // do smoething }

Answer 2

You can use less than(<) and greater than(>) operator basicly.

I mean you should change your if conditionlike:

if (d >= e && d <= DateTime.Now)

Answer 3

You can try something like this to compare Date portion without Time

string a = "-1"; // These are values that are configurable based on which date is checked. Yesterday means, -1 for example. 
string b = "-15"; // -15 means within last 15 days.
DateTime d = new DateTime();
DateTime e = d.AddDays(int.Parse(a));
if (DateTime.Now.Date >= d.Date && e.Date <= d.Date)
{

}