Combine multiple where conditions having optional parameters in C# linq?

Question

I am searching for a LINQ query where I have 3 parameters and two are optional parameters for this I wrote if-else conditions like below

if (id != null) { where condition} 
else if (name!= null) { where condition } 
else if (category != null) { where condition } 
else if (id != null && name != null) { where condition } 
else if (id != null && category != null) { where condition } 
else if (name != null && category != null) {where condition} 
else if (id != null && name != null && category != null ) { where condition }

I don't want to write more if-else conditions if there is another optional parameter added

Note. Id is not a primary key

Anyway, I think you might be looking for something like Where(x => (q == null || x.q == q) && ..) ; that is, the guards are moved INSIDE the filter. Otherwise CHAIN filters: f = ..; if (q != null) { f = f.Where(x => x.q == q); } — user2864740
– user2864740, Commented Mar 17, 2020 at 17:44

David Browne - Microsoft · Accepted Answer · 2020-03-17 19:44:47Z

2

The optimal pattern for this in EF is to add the Where conditions only conditionally. EG

IQueryable<SomeType> qry = ...;
if (id != null)
{
  qry = qry.Where(x => x.Id == id);
}
if (name != null)
{
  qry = qry.Where(x => x.Name == name);
}
if (category != null)
{
  qry = qry.Where(x => x.Category == category);
}
var results = qry.ToList();

That way you don't clutter up the expression with lots of predicates that don't do anything, but which can mess up the query execution.

answered Mar 17, 2020 at 19:44

David Browne - Microsoft

90.7k7 gold badges52 silver badges87 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Alex - Tin Le · Accepted Answer · 2020-03-17 18:29:22Z

1

What I always do is below. Easy to read and remember.

myList
    .Where(x => id == null || x.Id == id)
    .Where(x => name == null || x.Name == name)
    .Where(x => category == null || x.Category == category);

answered Mar 17, 2020 at 18:29

Alex - Tin Le

2,0101 gold badge8 silver badges11 bronze badges

Comments

Shervin Ivari · Accepted Answer · 2020-03-17 17:53:55Z

0

You can write it like this

id == null ? true : {id condition} &&
name == null ? true : {name condition} &&
category == null ? true: {category } and other conditions

Or

id == null || {id condition} &&
id == null || {id condition} &&

returning true will make the statement true if its value equals null. its clean, Easy to understand and develop.

I hope it helps.

answered Mar 17, 2020 at 17:53

Shervin Ivari

3,0915 gold badges30 silver badges43 bronze badges

Collectives™ on Stack Overflow

Combine multiple where conditions having optional parameters in C# linq?

3 Answers 3

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related