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c#linqlambda
Stacker
Stacker

Reputation: 8237

Like in Lambda Expression and LINQ

How can I do something like this using Expression trees :

customers.Where(c => c.Name **like** "john");

I know this isn't possible but I was wondering how can I have something similar.

Note : I'm NOT looking for solutions using SQL related LINQ queries (like Linq to SQL or Linq to entities)

Upvotes: 47

Views: 87313

Answers (7)

Rafael Parenza
Rafael Parenza

Reputation: 122

You can try this:

customers.where(c=>EF.Functions.Like(c.Name,"%john%");

I did a test to see the generated sql and this was the result

sql = _context.ProdutoPortfolio.Take(10).Where(c => c.NomeProduto.Contains(c.NomeProduto))

sql2 = _context.ProdutoPortfolio.Take(10).Where(c => EF.Functions.Like(c.NomeProduto, $"%{search}%")

Result sql1: If you use contains this is the result

DECLARE @__p_0 int = 10;
DECLARE @__search_1 varchar(350) = 'a';

 

SELECT [t].[ProductID], [t].[Cod], [t].[ProductName], [t].[SubThemeName], [t].[ThemeName]
FROM (
     SELECT TOP(@__p_0) [p].[ProductID], [p].[Cod], [p].[ProductName], [p].[SubThemeName], [p].[ThemeName]
     FROM [ProductPortfolio] AS [p]
) AS [t]
WHERE (@__search_1 LIKE '') OR (CHARINDEX(@__search_1, [t].[productName]) > 0)

Result sql2:

DECLARE @__p_0 int = 10;
DECLARE @__Format_2 varchar(350) = '%a%';

 

SELECT [t].[ProductID], [t].[Cod], [t].[ProductName], [t].[SubThemeName], [t].[ThemeName]
FROM (
     SELECT TOP(@__p_0) [p].[ProductID], [p].[Cod], [p].[ProductName], [p].[SubThemeName], [p].[ThemeName]
     FROM [ProductPortfolio] AS [p]
) AS [t]
WHERE [t].[productname] LIKE @__Format_2

SQL2 meets what I want, SQL2 wins

Upvotes: -1

AbdusSalam
AbdusSalam

Reputation: 440

Here is my code :

string s="somethings";

customers.Where(c => c.Name != null && c.Name.ToLower().Contains(s.ToLower()));

Somethings like that.

Upvotes: 1

Johannes Rudolph
Johannes Rudolph

Reputation: 35751

If you are targeting LINQ to SQL, use SqlMethods.Like:

customers.Where(c => SqlMethods.Like(c.Name, "%john%"));

Explanation:

The compiler will generate an expression tree from the statement above. Since LIKE is a SQL specific construct and not common to all LINQ Query providers, the SqlMethods class and its members are used as a "hint" for the expression compiler (compiles expression trees to SQL) to emit a LIKE statement.

Upvotes: 31

Dan Tao
Dan Tao

Reputation: 128377

The first thought that comes to mind is Regex.IsMatch.

This would come closest to providing the kind of functionality you get from LIKE; for instance with it you could do this:

var matches = people.Where(p => Regex.IsMatch(p.Name, "A.*[mn]"));

foreach (Person match in matches)
{
    Console.WriteLine(match.Name);
}

And get output like this:

Adam
Aaron
Aidan

Going with string.Contains as others have suggested is almost certainly preferable if your intention is simply to look for a specific substring within Name.

Upvotes: 10

Tom Vervoort
Tom Vervoort

Reputation: 5108

customers.Where(c => c.Name.Contains("john"));

Upvotes: 86

Andrei
Andrei

Reputation: 51

using System.Data.Linq.SqlClient;
...
customers.where(c=>SqlMethods.Like(c.Name, "john"));

Upvotes: 5

bitbonk
bitbonk

Reputation: 49639

Use Regex.IsMatch in your where statement or for a more simpler version without wildcards etc.:

customers.where(c=>c.Name.Contains("john"));

Upvotes: 3

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