Linq to SQL Error

User 11883281

I've got this Code:

System.Linq.IQueryable fdl = _db.object_localized_1_de.AsQueryable();
var artNrs = from item in fdl
where item.bedienungsanweisung.Contains(id)
&& item.article_number != null
select item.article_number;

But i get this error:

Could not find an implementation of the query pattern for source type 'System.Linq.IQueryable'. 'Where' not found. Consider explicitly specifying the type of the range variable 'item'.

Richard Deeming

What type of object does the object_localized_1_de collection contain? Either use the object type as the type parameter for the generic IQueryable<T> interface:

System.Linq.IQueryable<YOUR_TYPE_HERE> fdl = _db.object_localized_1_de.AsQueryable();

Or explicitly specify the type in the query:

var artNrs = from YOUR_TYPE_HERE item in fdl ...

Or use var to implicitly type the fdl variable:

var fdl = _db.object_localized_1_de.AsQueryable();

The first and third options will be identical. The second option will call the Cast method, which could affect the performance.

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

User 11883281

Okay thanks... But now i've this Code:

for (int i = 0; i < 3; i++)
{
var query = _db.object_localized_1_de.AsQueryable();
if (i == 1) { query = _db.object_localized_1_en.AsQueryable(); }
if (i == 2) { query = _db.object_localized_1_fr.AsQueryable(); }

var artNrs = from item in query
	where item.bedienungsanweisung.Contains(id)
	&& item.article\_number != null
	select item.article\_number;

//...

}

And got this Errors:

Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Linq.IQueryable'. An explicit conversion exists (are you missing a cast?)
Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Linq.IQueryable'. An explicit conversion exists (are you missing a cast?)

I don't want to use a cast, may you can help me please?

Richard Deeming

Your entities will have to implement a common interface, or inherit from a common base class, containing the properties you need to query:

interface ILocalizedObject
{
?PROPERTY_TYPE_HERE? bedienungsanweisung { get; }
?PROPERTY_TYPE_HERE? article_number { get; }
}

class object_localized_1_de : ILocalizedObject
{
...
}

class object_localized_1_fr : ILocalizedObject
{
...
}

class object_localized_1_en : ILocalizedObject
{
...
}

You'll then need to use that interface in your variable declaration:

for (int i = 0; i < 3; i++)
{
IQueryable<ILocalizedObject> query = _db.object_localized_1_de.AsQueryable();
if (i == 1) { query = _db.object_localized_1_en.AsQueryable(); }
if (i == 2) { query = _db.object_localized_1_fr.AsQueryable(); }

var artNrs = from item in query
    where item.bedienungsanweisung.Contains(id)
    && item.article\_number != null
    select item.article\_number;

...

}

This will work due to generic covariance[^].

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

User 11883281

I'm getting this error:

Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Linq.IQueryable'. An explicit conversion exists (are you missing a cast?)

Did I something wrong?

Richard Deeming

Looks like you forgot to make your entity class implement the interface.

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

User 11883281

Yes it works thank you...

ip address

:thumbsup: Super! Thanks!