Entity Framework v4.1 LIKE

问题

How do I have to build my query to result in an output SQL query like:

SELECT
[viewRegisters].[Id] AS [IdRegister]
WHERE Name LIKE '%a%bc'

OR

SELECT
[viewRegisters].[Id] AS [IdRegister]
WHERE Name LIKE 'a%b%c'

OR

SELECT
[viewRegisters].[Id] AS [IdRegister]
WHERE Name LIKE 'a%b%c%'

I'm using .Net Framework 4.0, Entity Framework v4.1 and C#.

EF v4.1 converts this type of linq queries from:

((IQueryable<T>)Data).Where(z => z.Field.Contains("a%b%c%"));

Into:

SELECT
[viewRegisters].[Id] AS [Id]
WHERE Name LIKE N'a~%b~%c~%' ESCAPE N'~'

That's not what I want. I want to be able to use the 'percent' symbol as I do directly in DB.

回答1:

You must use ESQL if you want full wildcard support. Linq-to-entities is not able to do that and EFv4.1 code first (without EDMX) doesn't have support for model defined functions so the solution provided by @Johann Blais cannot be used.

I guess the code to run ESQL query can look like:

string command = "SELECT VALUE e FROM ContextName.DbSetName AS e WHERE e.Field LIKE 'a%b%c%'"
ObjectContext ctx = ((IObjectContextAdapter)dbContext).ObjectContext;
ObjectQuery<EntityType> query = new ObjectQuery<EntityType>(command, ctx);
ObjectResult<EtntiyType> result = query.Execute(MergeOption.AppendOnly);

回答2:

If you are using SQL Server, use the PATINDEX function to do a pattern search. You can access this function through EF using the SqlFunctions class.

For example, the following EF query

context.ViewRegisters.Where(z => SqlFunctions.PatIndex("a%b%c%", z.Name) > 0);

will translate into

SELECT 
[Extent1].[Id] AS [Id], 
[Extent1].[Name] AS [Name]
FROM [dbo].[ViewRegisters] AS [Extent1]
WHERE (CAST(PATINDEX(N'a%b%c%', [Extent1].[Name]) AS int)) > 0

回答3:

var query = from viewRegister in context.ViewRegisters
where viewRegister.Name.Contains("yourname")
select viewRegister;

来源：https://stackoverflow.com/questions/6202036/entity-framework-v4-1-like