Linq query skip querying null coditions

Question

I am very new to linq. I have my clients table. I want to select clients depending on the two conditions

Client type
Client city

So I can write the query like

from c in clients
where c.Type == cType
&& c.City == cCity

Can I use this same query to get the result only providing client type(ignoring the City condition. somithing like *).

What I want to do is if cCity or cType is null ignore the condition.

Is this possible to do?

MarcinJuraszek · Accepted Answer · 2013-10-25 05:01:27Z

1

Isn't that what you're looking for?

from c in clients
where (c.Type == null || c.Type == cType)
&& (c.City == null || c.City == cCity)

answered Oct 25, 2013 at 5:01

MarcinJuraszek

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2 Comments

New Developer Over a year ago

I want if cType==null skip querying that condition

m4ngl3r Over a year ago

when c.Type is null the whole result of (c.Type == null || c.Type == cType) is True, Therefore it is replaced by True so it skips that and checks next condition chain.. and so on

Gert Arnold · Accepted Answer · 2013-10-25 07:30:21Z

0

You can compose a LINQ statement before actually executing it:

if (cType != null)
    clients = clients.Where(c => c.Type == cType);
if (cCity != null)
    clients = clients.Where(c => c.City== cCity);
// At this point the query is never executed yet.

Example of how the query can be executed for the first time :

var results = clients.ToList();

answered Oct 25, 2013 at 7:30

Gert Arnold

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Comments

Girish Sakhare · Accepted Answer · 2013-10-25 10:30:13Z

0

from c in clients
where (cType == null ? 1 == 1 : c.Type == cType)
&& (cCity == null ? 1 == 1 : c.City == cCity)

answered Oct 25, 2013 at 10:30

Girish Sakhare

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4 Comments

Sergey Berezovskiy Over a year ago

Can you explain what is benefit of hardcoding true value as 1 == 1? And benefit of ternary operation when it returns boolean value VS simple OR condition

Girish Sakhare Over a year ago

It something similar to @Gert answer. 1 == 1 is always true i.e. we are skipping the condition if cType or cCity is null.

Sergey Berezovskiy Over a year ago

I know that 1 == 1 is always true. Why not to write true instead: cType == null ? true : c.Type == cType? If cType is null, then we return true else we return c.Type == cType. But that is how OR works: cType == null || c.Type == cType. So, questions are still here.

Girish Sakhare Over a year ago

oh I misunderstood the question. Yup you are right we can have true there.

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