Newblie Linq Question - Intersecting to lists on partial matches

Question

I'm pretty new with Linq so forgive me if this is one of those "well, duh!" questions.

I have an IEnumerable<string> where each string represents someone's name in the format Lastname, Firstname.

I have another IEnumber<string> where each string represents a Last name

I'd like to get an IEnumerable<string> list of people's name whos last name are in my last names collection.

For example:

var LastNames = new [] {"Smith","Jones"}
var People = new [] {"Smith, Ted", "Jones, Bob", "Jones, Alan", "Kent, Clark"}

I'd like to end up with a list/array/Ienumerable containing "Smith, Ted", "Jones, Bob", and  "Jones, Alan".

The intersect operator seems close, but I believe it does full string matching.

Thanks.

Answer 1

from p in people
from l in lastNames
where p.StartsWith(l)
select p

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Kristofer - Huagati Systems Co., Ltd.
Cool tools for Linq-to-SQL and Entity Framework:
huagati.com/dbmltools (add-in with new features for Visual Studio 2008's L2S and EF designers)
huagati.com/L2SProfiler (Query profiler for Linq-to-SQL and LLBLGen Pro)

Answer 2

Hi Chris,

 

As you said, the Intersect use a full string match, so we cannot use it in such scenario unless we customize an IEqualityComparer(string). 

 

Two string comparison methods for your references:

================================================================
var query = People.Where(p => LastNames.Contains(p.Split(',')[0]));

 

var query2 = People.Where(p => LastNames.Contains(p.Substring(0, p.IndexOf(','))));
================================================================

 

Kristofer, for your method, how about if we have a LastNames array : {“Smith, Jone”}  ?  J

 

 

Have a nice day!

 

 

Best Regards,
Lingzhi Sun

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Answer 3

 

Kristofer, for your method, how about if we have a LastNames array : {“Smith, Jone”}  ?  J

That's why there's a join hidden in there... :)

from p in people
from l in lastNames
where p.StartsWith(l)
select p

...will do an inner join between the people and lastname arrays, with the join criteria that the returned 'people' elements start with the lastname element that it is joined to.

---

Kristofer - Huagati Systems Co., Ltd.
Cool tools for Linq-to-SQL and Entity Framework:
huagati.com/dbmltools (add-in with new features for Visual Studio 2008's L2S and EF designers)
huagati.com/L2SProfiler (Query profiler for Linq-to-SQL and LLBLGen Pro)

Answer 4

Hi Kristofer,

I don't quite understand the INNER JOIN here.  Can you explain more?   I used the LastNames array: { "Smith", "Jone" }, but the query returns three people, "Smith, Ted", "Jones, Bob", "Jones, Allen".  I think it should only return "Smith, Ted".    

 

Have a nice day!

 

Best Regards,
Lingzhi Sun

MSDN Subscriber Support in Forum

If you have any feedback on our support, please contact [e-mail]

---

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Answer 5

Ah, ok, I see what you mean.

from p in people
from l in lastNames
where p.StartsWith(l + ",")
select p

..then...

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Kristofer - Huagati Systems Co., Ltd.
Cool tools for Linq-to-SQL and Entity Framework:
huagati.com/dbmltools (add-in with new features for Visual Studio 2008's L2S and EF designers)
huagati.com/L2SProfiler (Query profiler for Linq-to-SQL and LLBLGen Pro)

Answer 6

Hi Chris,

 
How is the problem now?   If you need any further assistance, please feel free to let me know. 

 

Have a nice day!

 

 

Best Regards,
Lingzhi Sun

MSDN Subscriber Support in Forum

If you have any feedback on our support, please contact [e-mail]

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Answer 7

Thanks for the response.  You've answered my question.