multiple conditions Linq extended - linq

Question

I need to consider multiple conditions to get value.
i mean if all conditions true that must give me a filtered answer.
Or one of them is true,rest are false...
so i need to write all possibilities??
if(a&b&c&d) else if(a&b&c) else if(a&c&d) else if(b&c&d) else if(a&b) else if (a&c)...etc ?? :))) Is there a shorter way to do this?
public List<ProductReqNoDate> GetRequestsQuery(string departmant, int reqStateID, string firstDate, string lastDate, string productName)
{
var db = new requestDBEntities();
bool dp = !string.IsNullOrEmpty(departmant);
bool pr = !string.IsNullOrEmpty(productName);
bool tm = !string.IsNullOrEmpty(firstDate) && !string.IsNullOrEmpty(lastDate);
bool rs = reqStateID > 0 ? true : false;
var query = (from r in db.requests
select new ProductReqNoDate
{
departmant = r.departmant,
reqNo = r.reqNo,
reqDate = r.reqDate,
productName = (from p in db.products where p.reqNo == r.reqNo select p.productName).FirstOrDefault()
}).ToList();
if (dp & pr & tm & rs)
{
var rState = (from ta in db.reqStates
where ta.reqStateID == reqStateID && ta.isActive == true
select ta.reqNo).ToList();
var prName = (from p in db.products where p.productName.Contains(productName) select p.reqNo).ToList();
DateTime dtfirstDate = Convert.ToDateTime(firstDate);
DateTime dtlastDate = Convert.ToDateTime(lastDate);
return query.Where(
r => rState.Contains(r.reqNo) //find by Request State
&& r.departmant == departmant //find by Departmant
&& (r.reqDate >= dtfirstDate && r.reqDate <= dtlastDate) //find by Date
&& prName.Contains(r.reqNo) //Find By Product Name
).ToList();
}
else if (dp & pr & tm) { /*return query.Where(...} */}
else if (pr & tm & rs) { /*return query.Where(...} */}
else if (dp & pr && rs) { /*return query.Where(...} */}
else if (dp & pr) { /*return query.Where(...} */}
//else if ...etc
}

Answer 1

Just add one Where condition at a time
public List<ProductReqNoDate> GetRequestsQuery(string departmant, int reqStateID, string firstDate, string lastDate, string productName)
{
var db = new requestDBEntities();
bool dp = !string.IsNullOrEmpty(departmant);
bool pr = !string.IsNullOrEmpty(productName);
bool tm = !string.IsNullOrEmpty(firstDate) && !string.IsNullOrEmpty(lastDate);
bool rs = reqStateID > 0 ? true : false;
var query = (from r in db.requests
select new ProductReqNoDate
{
departmant = r.departmant,
reqNo = r.reqNo,
reqDate = r.reqDate,
productName = (from p in db.products where p.reqNo == r.reqNo select p.productName).FirstOrDefault()
}).AsQueryable(); //AsQueryable is not always needed, but it shouldn't hurt and I don't feel like checking for this example.
if (dp)
{
query = query.Where(q => /*condition*/);
}
if (pr)
{
query = query.Where(q => /*condition*/);
}
if (tm)
{
query = query.Where(q => /*condition*/);
}
if (rs)
{
query = query.Where(q => /*condition*/);
}
return query.ToList();
}

Answer 2

You can build an expression with Expression.And like:
private Expression<Func<Request, bool>> GetPredicate(FilterDto filter)
{
Expression<Func<Request, bool>> predicate = r => r.ID == r.ID;
if (filter.Department.HasValue)
predicate = predicate.And(r => r.Department == filter.Department.Value);
if (filter.FirstDate.HasValue)
predicate = predicate.And(r => (r.reqDate >= filter.FirstDate.Value));
if (filter.LastDate.HasValue)
predicate = predicate.And(r => (r.reqDate <= filter.LastDate.Value));
/* ... */
return predicate;
}
Note: I put r => r.ID == r.ID here as first expression, just to have an expression to start with. This snippet does not fully cover your code, but I think it is enough as an example.
Use the expression in return query.Where(expression).ToList().