I have column search filter values sent to my web api and I can't figure how to make the where clause dynamic?
Look below (too much code)!!
Name Value Collection:
public DataTablePager<AccountDTO> Get([FromUri] DataTableParameter param)
{
NameValueCollection nvc = HttpUtility.ParseQueryString(Request.RequestUri.Query);
Casting the search values:
if (!String.IsNullOrEmpty(nvc["sSearch_0"]) && !int.TryParse(nvc["sSearch_0"], out tmpInt) ||
!String.IsNullOrEmpty(nvc["sSearch_1"]) && !int.TryParse(nvc["sSearch_1"], out tmpInt) ||
!String.IsNullOrEmpty(nvc["sSearch_10"]) && !int.TryParse(nvc["sSearch_10"], out tmpInt)
Setup Where Clause:
filteredresults = filteredresults.Where(i => CorrectNumericTypes
&& (Lead_ID == null || i.Lead_ID == Lead_ID)
&& (Account_ID == null || i.Account_ID == Account_ID)
This is a classic case for the Pipes and Filters Architectural pattern.
You can construct a list of filters based on dynamic (runtime) conditions. Or keep a static list of filters, the ones where there is no criteria, the data just passes through. Apply this list of filters on the data set or the Query.
I don't think you can achieve that with LINQ. You can design a query builder (using the same Filters pattern)
Here's what I needed (predicate): http://www.c-sharpcorner.com/UploadFile/c42694/dynamic-query-in-linq-using-predicate-builder/
Related
I have a LINQ query which works fine as for stand alone lists but fails for CRM
var lst = new List<bool?>();
lst.Add(null);
lst.Add(true);
lst.Add(false);
bool IsWet = false;
var newlst = from exch_HideVoiceSignature in lst where
(((exch_HideVoiceSignature!=null && exch_HideVoiceSignature==false
|| exch_HideVoiceSignature== null) )&& !IsWet) select exch_HideVoiceSignature;
newlst.Dump();
var question = from q in exch_questionSet where ((q.exch_HideVoiceSignature != null
&& q.exch_HideVoiceSignature.Value == 0 )|| q.exch_HideVoiceSignature == null )
&& !IsWet select q.exch_HideVoiceSignature;
question.FirstOrDefault().Dump();
As you can see I can pass the variable IsWet to LINQ query for a standard list fine and get values for first list. But when I execute the same for second list, I get the following error
Invalid 'where' condition. An entity member is invoking an invalid property or method
The CRM LINQ provider won't support the evaluation you attempting. It only supports evaluation of where criteria is evaluating an entity field.
That's not a problem. Since you want the LINQ query to only use the where clause if IsWet is false (correct me if I'm wrong on that.) So we simply do the evaluation to determine if the where clause should be added or not. Then execute your query.
var question = from q in exch_questionSet
select q.exch_HideVoiceSignature;
if (!IsWet)
{
question.Where(x => ((x.exch_HideVoiceSignature != null
&& x.exch_HideVoiceSignature.Value == 0) || x.exch_HideVoiceSignature == null));
}
question.FirstOrDefault().Dump();
I am constantly confronted with that problem.
Try to "detach" (for example call .ToArray()) your query (while it is "clear") from CRM and then filter query using external parameter. This should help.
var question =
(from q in exch_questionSet
where (
(q.exch_HideVoiceSignature != null && q.exch_HideVoiceSignature.Value == 0 ) ||
q.exch_HideVoiceSignature == null )
select q.exch_HideVoiceSignature
).ToArray().Where(q => !IsWet);
question.FirstOrDefault().Dump();
UPDATE
If you are using IsWet flag to control blocks of conditions (enable and disable them from the one point in the code) then probably you may be interested in class named PredicateBuilder which allows you to dynamically construct predicates.
Just because I had an existing query with lot of other joins etc. and I wanted to pass this additional parameter to it I ended up using a var statement which dumps the rows to a list and applies the where clause in the same statement
bool IsWet =true ;
var question = ...existing query ...
select new {
...existing output ...,
Wet =q.exch_HideVoiceSignature != null &&
q.exch_HideVoiceSignature.Value == 119080001,
Voice = q.exch_HideVoiceSignature == null ||
(q.exch_HideVoiceSignature != null &&
q.exch_HideVoiceSignature.Value == 119080000) ,
}
;
var qq = IsWet ?
question.ToList().Where(X=> X.Wet ) :
question.ToList().Where(X=> X.Voice );
qq.FirstOrDefault().Dump();
I am trying to do something like this:
from t in ent.myEntities
where SelectedProperties == null || SelectedProperties.Any(le => le == t.Entity)
select t
basically trying to cover 2 cases. accepting an empty list, should return all entities, or filter on the list if it is supplied.
above actually does work when i supply the list, however in the case when it is null i get:
Unable to create a constant value of type
'System.Collections.Generic.List`1'. Only primitive types ('such as
Int32, String, and Guid') are supported in this context
also tried using this with a string array:
where arr == null || arr.Contains(t.Entity)
is it possible to have such a condition without having to build a predicate (which is a bigger effort)?
You might want to try using the list in a simpler way:
where SelectedProperties == null || SelectedProperties.Contains(t.Entity)
It may well not work, but it's worth a try. Otherwise, if this is really your whole query, I'd just write it as:
var query = SelectedProperties == null
? ent.myEntities
: ent.myEntities.Where(t => SelectedProperties.Contains(t.Entity));
EDIT: Okay, if you have to use Any, and have lots of these to compose, you can do it like this:
var query = ent.myEntities;
if (SelectedProperties != null)
{
query = query.Where(t => SelectedProperties.Any(x => x == t.Entity));
}
if (SomethingElse)
{
query = query.Where(...);
}
// etc
I'm using EF5, something like this will fix the issue:
ent.myEntities.ToList().Where(t => SelectedProperties == null || SelectedProperties.Contains(t.Entity));
I am implementing sort based on parameter passed to ascending or descending OrderBy method
else if (showGrid.Sortdir == "DESC")
{
alerts = DB.Incidents.OfType<Alert>().Where(
a =>
a.IncidentStatusID == (int)AlertStatusType.New ||
a.IncidentStatusID == (int)AlertStatusType.Assigned ||
a.IncidentStatusID == (int)AlertStatusType.Watching)
.OrderByDescending(a => showGrid.Sort);
}
else
{
alerts = DB.Incidents.OfType<Alert>().Where(
a =>
a.IncidentStatusID == (int)AlertStatusType.New ||
a.IncidentStatusID == (int)AlertStatusType.Assigned ||
a.IncidentStatusID == (int)AlertStatusType.Watching)
.OrderBy(a => showGrid.Sort);
}
In case of ascending order sorting it works fine but for descending order sorting doesn't work. I debugged the code and I found that list is not revered its same as ascending order. Please help me
Ok. I've written a small test. It is funny, but your code can actually compile and work, but very differently from what you expect :)
Obviously showGrid is not of type Alert, it is an instance of some other class, that incidentally have the same propery as Alert, called Sort.
First I was confused, because expected this code to fail to compile.
// The signature of OrderBy
public static IOrderedQueryable<TSource> OrderBy<TSource, TKey>(this IQueryable<TSource> source, Expression<Func<TSource, TKey>> keySelector)
// In your case it will result in
public static IOrderedQueryable<Alert> OrderBy<Alert, string>(this IQueryable<Alert> source, Expression<Func<Alert, string>> keySelector)
//when you call it like you do
DB.Incidents.OfType<Alert>().OrderByDescending(a => showGrid.Sort);
// You supply a property from object of type different from your entity.
// This is incorrect usage, the only object you can use here is the
// "a" argument. Like this:
DB.Incidents.OfType<Alert>().OrderByDescending(a => a.Sort);
// Because anything else does not make any sense to entity provider.
So your order by simply does not work.
As far as I understood, what you want is to perform sorting based on selection in UI. This is not easily achieved in strongly-typed LINQ. Because as I showed above, you send a property, not a value to the OrderBy. It does not care about the value inside the prop. So there are several solutions to the problem:
Write a big switch, that will check every possible Sort value, and will append appropriate 'OrderBy(a => a.YouPropToSort)' to the query. This is straitforward, and you should begin with this. Of course this is a static way, and will require to change code everytime you want new columns to be added for sorting.
Create argument for your OrderBy using 'LINQ Expression Trees'. For you case it should not be very hard to do. Look for the term, you will find a lot of examples.
Try to use Dynamic LINQ. I did not not use it myself, just looked at the docs. This seems to be an extension to the normal LINQ which allows you to write parts of queries as strings, to overcome limitations like the current one with dynamic sorting.
Here's my solution to sorting based on user selections:
Create your base query
var query = DB.Incidents.OfType<Alert>.Where(
a =>
a.IncidentStatusID == (int)AlertStatusType.New ||
a.IncidentStatusID == (int)AlertStatusType.Assigned ||
a.IncidentStatusID == (int)AlertStatusType.Watching);
and then apply your sort using a case statement
bool desc = showGrid.SortDir = "DESC";
switch(showGrid.Sort)
{
case "col1":
query = desc ? query.OrderByDescending( a => a.Col1 ) : query.OrderBy( a => a.Col1 );
break;
case "col2":
query = desc ? query.OrderByDescending( a => a.Col2 ) : query.OrderBy( a => a.Col2 );
break;
...
}
var results = query.ToList();
I have a linq statement that returns a list of records based on where clause
This where clause checks for two parameter values.
Out of which one parameter is optional.
so i need a suggestions if i can switch my where clause based on the optional Parameter
something like this
if(locid==0)
{
where (p.CustomerID == custid)
}
else{
where (p.CustomerID == custid) & (p.LocationID == locid )
}
can any one help me how can i get this work.
thanks
You could try writing it like this:
where (p.CustomerID == custid) && (locid == 0 || p.LocationID == locid )
Yes - queries can be composed (although you don't need this for this particular case as #rsbarro pointed out):
var query = p;
if(locid==0)
query = query.Where( p =>p.CustomerID == custid);
else
query = query.Where( p =>p.CustomerID == custid & p.LocationID == locid);
//any other conditions
As BrokenGlass mentioned, you should use composition:
IQueryable<Foo> query = unfiltered.Where(p => p.CustomerID == custId);
if (locid != 0)
{
query = query.Where(p => p.LocationID == locid);
}
Note that the query is not executed until you start reading data from it, so you needn't worry about this making multiple requests.
It looks like in your original post you were trying to use query syntax piecemeal - that won't work, but the "dot notation" is pretty simple here. You can always create your initial query using a query expression if you want - again, that query won't be executed immediately anyway.
I have a query, which throws an exception in Linq to Sql.
Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator.
I have seen plenty of related questions so I (roughly) understand the reason WHY it doesn't work (the value term in the lambda expression cannot be converted into a string value for the SQL query), but I cannot see HOW to should restructure this.
var searchTerms = userQuery.Split(' ').ToList().ConvertAll(term => term.ToLower());
var qry = (from tree in someQueryable
join widget in myDb.Widgets
on tree.ParentId equals widget.Id
where
searchTerms.All(term => tree.Title.ToLower().Contains(term) //Can't use Contains on term, as term isn't a local variable
|| searchTerms.All(term => widget.Title.ToLower().Contains(term) //And again here
|| (tree.Description != null && searchTerms.All(term =>
tree.Description.ToLower().Contains(term))) //And here
orderby tree.SomeDate descending
select tree);
How can I get all trees whose Title, Description or ParentWidget.Title contain ALL of the search terms?
I have tried iterating over each term, however this gives me the issue of matching a single term, not all terms.
Update
I resolved the issue... by changing my requirements :)
I am still very interested to know how my initial requirements could be achieved.
from term in SearchTerms
from tree in someQueryable
join widget in myDb.Widgets
where tree.Title.ToLower().Contains(term) ||
widget.Title.TowLower().Contains(term) ||
(tree.Description != null && tree.Description.ToLower.Contains(term))
orderby tree.SomeDate descending
select tree