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Lost_In_Library
Lost_In_Library

Reputation: 3493

How can I return asQueryable without LoadSelect?

I'm using lastest ServiceStack OrmLite(currently v4.5.6) with C#

I need to return asQueryable from a method, such as; 

    using (IDbConnection databaseConnection = _databaseFactory.Open())
    {
        SqlExpression<T> sqlExpression = databaseConnection.From<T>();

        IQueryable<T> asQueryable = databaseConnection.LoadSelect(sqlExpression, include)
                                                      .AsQueryable();

        return asQueryable;
    }

But as you can see, loadSelect already going to sql server like;
Select PARAMSetc FROM Table

So I just need IQueryable without going to sql server. I did it with Entity Framework, here is the code; 

public IQueryable<T> GetAll(Expression<Func<T, bool>> predicate)
{
    return _dbSet.Where(predicate);
}

And yes, I'm writing a kind of generic repository wrapper and I know repository patterns should not return IQueryable because someone use this method and could make performance errors etc. This is out of my topic right now.

How can I return IQueryable with OrmLite ?

Upvotes: 4

Views: 921

Answers (2)

mythz
mythz

Reputation: 143399

OrmLite uses it's own typed API for querying using either simple lambda expressions for simple queries:

var results = db.Select<Poco>(x => x.Id == 1);

Or a Typed SqlExpression<T> which provides a Typed API modeled closely over SQL which also uses LINQ-like lambda expressions to provide a typed, rich API for querying RDBMS's, e.g:

var q = db.From<Track>()
    .Where(x => customYears.Contains(x.Year))
    .And(x => x.Name.Contains("A"))
    .GroupBy(x => x.Year)
    .OrderByDescending("Total")
    .ThenBy(x => x.Year)
    .Take(2);

var results = db.Select(q);

OrmLite doesn't implement IQueryable<T>, if you need an SQL IQueryable<T> implementation you'll need to use an ORM that implements it like EF.

The only way to get an IQueryable<T> in any other ORM is to return it convert from a .NET List<T> that OrmLite returns, e.g:

List<Poco> results = db.Select<Poco>();
IQueryable<Poco> queryable = results.AsQueryable();

Upvotes: 2

Murat G&#252;ndeş
Murat G&#252;ndeş

Reputation: 859

I saw a post like this; here

Firstly there's no IQueryable or Linq in OrmLite it's pretty much just using SQL or filters. Methods with "Each" in them return back a lazily evaluated list.

Generally you just query by passing in a "where sql", "anon types" or full sql, eg:

var results = dbCmd.Select<Poco>("Name = {0}", name);
var results = dbCmd.Where<Poco>("Name", name);
var results = dbCmd.Where<Poco>(new { Name = name });
var results = dbCmd.Select<Poco>("Select * from Poco Where Name = {0}", name);
var results = dbCmd.Query<Poco>("Select * from Poco Where Name = @name", new { name });

For building of queries the latest version uses a SqlBuilder class which @samsaffron talks about here: http://samsaffron.com/archive/2011/09/05/Digging+ourselves+out+of+the+mess+Linq-2-SQL+created

You can return a builder class that other code uses to construct the query and then use the builder output in a new dbCmd query, example:

var count = dbCmd.QuerySingle<Poco>(count.RawSql, count.Parameters);
var rows = dbCmd.Query<Poco>(selector.RawSql, selector.Parameters);

Micro ORM's are not for everyone and if you have existing code using IQueryable, it might be better to just leave it as-is.

Upvotes: 1

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