asp.net core LINQ where clause

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asp.net core LINQ where clause

Abdullah Durrani 41

I'm new to asp.net and learning from pluralsight and instructor uses this LINQ query which I can't understand .
public IEnumerable<Restaurant> GetRestaurantsByName(string name = null)
{
return from r in restaurants
where string.IsNullOrEmpty(name) || r.Name.StartsWith(name)
orderby r.Name
select r;
}
I can't understand the where part. What does it do especially the first part string.IsNullOrEmpty(name)

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Answer 1

Yiyi You - MSFT 521

Hi,AbdullahDurrani-7930,

GetRestaurantsByName gets restaurants with name.Firstly you need to check if name is empty or null with string.IsNullOrEmpty(name),if it is null or empty,you only need to return all restaurants.If it is not null or empty,you need to get restaurants with name.So there is a || between string.IsNullOrEmpty(name) and r.Name.StartsWith(name).Only when name is not null or empty,it will check r.Name with r.Name.StartsWith(name).

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YiyiYou

Abdullah Durrani 41 Reputation points

2021-09-13T10:36:20.273+00:00

So if the first part is true it skips the next part after || ??
Bruce (SqlWork.com) 83,821 Reputation points

2021-09-13T20:11:19.687+00:00

yes.

sqlserver supports expression short-circuits. with an "or" expression, it skips on the first true, with an "and" expression, skips on the first false.
Yiyi You - MSFT 521 Reputation points

2021-09-14T01:31:09.37+00:00

Hi,AbdullahDurrani-7930,

yes,if the first part is true it skips the next part after ||.
Abdullah Durrani 41 Reputation points

2021-09-14T01:43:40.17+00:00

Got it. Thank you

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