Develop Reference

PetaPOCO and more than 4 joins

Is petapoco capable of achieving the following :
1.Unlimited joins in one query
2.Unlimited One to Many relations in one query
I have looked at PetaPOCO and it seems like it is not capable of doing more than 4 joins, the longest signature looks like :
db.Query<T1, T2, T3 , T4>
Also seems like it supports a one to many relation , but only for one composite object such as below :
db.FetchOneToMany<T1, T2> where T2 is a foreign key of T1
I'm testing some of the micro ORMs out there to stick to the best one. Do you know of any of them that can handle these situations and if none of the micro ORMs are supporting this feauture, how do you deal with an object that is like the following :
class A
{
List<B> member1;
List<C> member2;
Z member3; //Composit object
Z1 member4; //Composit object
Z2 member5; //Composit object
Z3 member6; //Composit object
Z4 member7; //Composit object
}
And then even more complicated is , what if member one (type B) has some composite object within itself ? What if we have :
class B
{
G member0;
}
Please don't propose a solution to hit database multiple times, coz it's going to be way too many calls when the objects become just a little bit complex.
Oh and i also know that one other way of tackling the case of unlimited joins is creating a very flat object that hols all fields combined. It's not an elegant solution at all.

The T1..T$ Query() overloads all pass through to the main Query(..Type[]..) method. You can either add more Query() overloads yourself to handle more T parameters, or pass in all the types you need in a Type array (which is what the T1-T4 functions do) :
Query<TRet>( new Type[]{typeof(Poco1), typeof(Poco2), typeof(Poco3), typeof(Poco4), typeof(Poco5)}, null, sql, args);
You can have multiple one to many relationships but Schotime is right, you need to be very careful of swathes of duplicate data coming back in your result set. Write the sql query and look at the result set, is the amount of duplication acceptable to you? If so then in Petapoco there is a concept of relator callbacks where you write a small class that handles the different pocos in a single result row and add each poco to the list properties on the parent poco.
http://www.toptensoftware.com/Articles/115/PetaPoco-Mapping-One-to-Many-and-Many-to-One-Relationships
I've never had to do this with multiple one to many but quoted from the above
"If you're joining more than two tables you'll need something more
complex but it's really just extensions of the above."
Another option is to have a stored procedure that does all the work in a single database request and have it return multiple result sets which I believe Schotime has achieved in his branch of petapoco but I've not used it myself yet so I can't really comment on if it will help here :
http://schotime.net/blog/index.php/2011/11/20/petapoco-multiple-result-sets/
If I absolutely had to wire up all the data in one go for objects as complex and nested as you are suggesting then I would use a stored procedure (a single db call) and stitch it all together with code. Only then would I figure out how to do this in Petapoco. However if your UI doesn't show all the nested data until the user clicks on an expander button (or similar) I'd use an AJAX call at that point rather than get all the data initially.

The answer is correct, but I came to this page from another forum and no one there could make this work, so I thought I would chip in what I did to make things clearer. Basically, I had code like the following:
var sql = "select * from someTable where tableId = #0";
var listOfStuff = _petapoco.Fetch<FirstType, SecondType, ThirdType, FourthType, FirstType>(new RelatorClass().MapIt, sql, idVar);
Since I needed to add in a fifth poco, and all the Fetch methods eventually lead to the master Query method listed above in the accepted answer, I had to do this:
var sql = "select * from someTable where tableId = #0";
Func<FirstType, SecondType, ThirdType, FourthType, FifthType, FirstType> mapIt = new RelatorClass().MapIt;
var listOfStuff = _petapoco.Query<FirstType>(new[] { typeof (FirstType), typeof (SecondType), typeof (ThirdType), typeof (FourthType), typeof(FifthType)}, mapIt, sql, idVar).ToList();
Now I can query with 5 pocos and I didn't have to modify the PetaPoco code. The only other thing to do would be to add to your relator class so you can tell PetaPoco where to map the new data and you're good to go.

Delegate:
Note: you don't have to return the (UserActivity,int) anonymous type like this, you can return a single type without the parenthesis! I'm just lazy and don't want to create a new model for the return type.
private delegate (UserActivity, int) GetIt(int fk_AccountTypeValue, UserActivityModel ua, User u, Client c, Client_Account ca);
SQL Operation:
public List<(UserActivity,int)> SomeMethodName(int orgnizationID)
{
var sql = Sql.Builder
.Select("TOP(200) at.FK_AccountTypeValue, ua.*, u.*, c.*, ca.*")
.From("UserActivity ua")
.LeftJoin("Users u").On("u.PK_UserID = ua.FK_UserID")
.LeftJoin("Client c").On("c.FK_UserID = u.PK_UserID")
.LeftJoin("Client_Account ca").On("ca.FK_ClientID = c.PK_ClientID")
.LeftJoin("AccountType at").On("at.PK_AccountType = c.FK_AccountTypeID")
.Where("u.FK_OrganizationID =#0", orgnizationID)
.OrderBy("ua.Timestamp desc");
GetIt obj = new GetIt(youKnowIt);
var typs = new Type[]{typeof(int), typeof(UserActivityModel), typeof(User), typeof(Client), typeof(Client_Account)};
var uaList = _database.Query<(UserActivity, int)>(typs, obj, sql.SQL, sql.Arguments).ToList();
return uaList;
}
Method pointed to by the delegate:
private (UserActivity,int) youKnowIt(int fk_AccountTypeValue, UserActivityModel ua, CurrentDesk.Models.User u, CurrentDesk.Models.Client c, CurrentDesk.Models.Client_Account ca)
{
// do stuff
var uam = new UserActivity()
{
// assign stuff
};
return (uam, fk_AccountTypeValue);
}

Retrieve an object from entityframework without ONE field

I'm using entity framework to connect with the database. I've one little problem:
I've one table which have one varbinary(MAX) column(with filestream).
I'm using SQL request to manage the "Data" part, but EF for the rest(metadata of the file).
I've one code which has to get all files id, filename, guid, modification date, ... of a file. This doesn't need at all the "Data" field.
Is there a way to retrieve a List but without this column filled?
Something like
context.Files.Where(f=>f.xyz).Exclude(f=>f.Data).ToList();
??
I know I can create anonymous objects, but I need to transmit the result to a method, so no anonymous methods. And I don't want to put this in a list of anonymous type, and then create a list of my non-anonymous type(File).
The goal is to avoid this:
using(RsSolutionsEntities context = new RsSolutionsEntities())
{
var file = context.Files
.Where(f => f.Id == idFile)
.Select(f => new {
f.Id, f.MimeType, f.Size, f.FileName, f.DataType,
f.DateModification, f.FileId
}).FirstOrDefault();
return new File() {
DataType = file.DataType, DateModification = file.DateModification,
FileId = file.FileId, FileName = file.FileName, Id = file.Id,
MimeType = file.MimeType, Size = file.Size
};
}
(I'm using here the anonymous type because otherwise you will get a NotSupportedException: The entity or complex type 'ProjectName.File' cannot be constructed in a LINQ to Entities query.)
(e.g. this code throw the previous exception:
File file2 = context.Files.Where(f => f.Id == idFile)
.Select(f => new File() {Id = f.Id, DataType = f.DataType}).FirstOrDefault();
and "File" is the type I get with a context.Files.ToList(). This is the good class:
using File = MyProjectNamespace.Common.Data.DataModel.File;
File is a known class of my EF datacontext:
public ObjectSet<File> Files
{
get { return _files ?? (_files = CreateObjectSet<File>("Files")); }
}
private ObjectSet<File> _files;

Is there a way to retrieve a List but without this column filled?
Not without projection which you want to avoid. If the column is mapped it is natural part of your entity. Entity without this column is not complete - it is different data set = projection.
I'm using here the anonymous type because otherwise you will get a
NotSupportedException: The entity or complex type 'ProjectName.File'
cannot be constructed in a LINQ to Entities query.
As exception says you cannot project to mapped entity. I mentioned reason above - projection make different data set and EF don't like "partial entities".
Error 16 Error 3023: Problem in mapping fragments starting at line
2717:Column Files.Data in table Files must be mapped: It has no
default value and is not nullable.
It is not enough to delete property from designer. You must open EDMX as XML and delete column from SSDL as well which will make your model very fragile (each update from database will put your column back). If you don't want to map the column you should use database view without the column and map the view instead of the table but you will not be able to insert data.
As a workaround to all your problems use table splitting and separate the problematic binary column to another entity with 1 : 1 relation to your main File entity.

I'd do something like this:
var result = from thing in dbContext.Things
select new Thing {
PropertyA = thing.PropertyA,
Another = thing.Another
// and so on, skipping the VarBinary(MAX) property
};
Where Thing is your entity that EF knows how to materialize. The resulting SQL statement shouldn't include the large column in its result set, since it's not needed in the query.
EDIT: From your edits, you get the error NotSupportedException: The entity or complex type 'ProjectName.File' cannot be constructed in a LINQ to Entities query. because you haven't mapped that class as an entity. You can't include objects in LINQ to Entities queries that EF doesn't know about and expect it to generate appropriate SQL statements.
You can map another type that excludes the VarBinary(MAX) column in its definition or use the code above.

you can do this:
var files = dbContext.Database.SqlQuery<File>("select FileId, DataType, MimeType from Files");
or this:
var files = objectContext.ExecuteStoreQuery<File>("select FileId, DataType, MimeType from Files");
depending on your version of EF

I had this requirement because I have a Document entity which has a Content field with the content of the file, i.e. some 100MB in size, and I have a Search function that I wanted to return the rest of the columns.
I chose to use projection:
IQueryable<Document> results = dbContext.Documents.Include(o => o.UploadedBy).Select(o => new {
Content = (string)null,
ContentType = o.ContentType,
DocumentTypeId = o.DocumentTypeId,
FileName = o.FileName,
Id = o.Id,
// etc. even with related entities here like:
UploadedBy = o.UploadedBy
});
Then my WebApi controller passes this results object to a common Pagination function, which applies a .Skip, .Take and a .ToList.
This means that when the query gets executed, it doesn't access the Content column, so the 100MB data is not being touched, and the query is as fast as you'd want/expect it to be.
Next, I cast it back to my DTO class, which in this case is pretty much exactly the same as the entity class, so this might not be a step you need to implement, but it's follows my typical WebApi coding pattern, so:
var dtos = paginated.Select(o => new DocumentDTO
{
Content = o.Content,
ContentType = o.ContentType,
DocumentTypeId = o.DocumentTypeId,
FileName = o.FileName,
Id = o.Id,
UploadedBy = o.UploadedBy == null ? null : ModelFactory.Create(o.UploadedBy)
});
Then I return the DTO list:
return Ok(dtos);
So it uses projection, which might not fit the original poster's requirements, but if you're using DTO classes, you're converting anyway. You could just as easily do the following to return them as your actual entities:
var dtos = paginated.Select(o => new Document
{
Content = o.Content,
ContentType = o.ContentType,
DocumentTypeId = o.DocumentTypeId,
//...
Just a few extra steps but this is working nicely for me.

For EF Core 2
I implemented a solution like this:
var files = context.Files.AsNoTracking()
.IgnoreProperty(f => f.Report)
.ToList();
The base idea is to turn for example this query:
SELECT [f].[Id], [f].[Report], [f].[CreationDate]
FROM [File] AS [f]
into this:
SELECT [f].[Id], '' as [Report], [f].[CreationDate]
FROM [File] AS [f]
you can see the full source code in here:
https://github.com/aspnet/EntityFrameworkCore/issues/1387#issuecomment-495630292

I'd like to share my attempts to workaround this problem in case somebody else is in the same situation.
I started with what Jeremy Danyow suggested, which to me is the less painful option.
// You need to include all fields in the query, just make null the ones you don't want.
var results = context.Database.SqlQuery<myEntity>("SELECT Field1, Field2, Field3, HugeField4 = NULL, Field5 FROM TableName");
In my case, I needed a IQueryable<> result object so I added AsQueryable() at the end. This of course let me add calls to .Where, .Take, and the other commands we all know, and they worked fine. But there's a caveat:
The normal code (basically context.myEntity.AsQueryable()) returned a System.Data.Entity.DbSet<Data.DataModel.myEntity>, while this approach returned System.Linq.EnumerableQuery<Data.DataModel.myEntity>.
Apparently this means that my custom query gets executed "as is" as soon as needed and the filtering I added later is done afterwards and not in the database.
Therefore I tried to mimic Entity Framework's object by using the exact query EF creates, even with those [Extent1] aliases, but it didn't work. When analyzing the resulting object, its query ended like
FROM [dbo].[TableName] AS [Extent1].Where(c => ...
instead of the expected
FROM [dbo].[TableName] AS [Extent1] WHERE ([Extent1]...
Anyway, this works, and as long as the table is not huge, this method will be fast enough. Otherwise you have no option than to manually add the conditions by concatenating strings, like classic dynamic SQL. A very basic example in case you don't know what I'm talking about:
string query = "SELECT Field1, Field2, Field3, HugeField4 = NULL, Field5 FROM TableName";
if (parameterId.HasValue)
query += " WHERE Field1 = " + parameterId.Value.ToString();
var results = context.Database.SqlQuery<myEntity>(query);
In case your method sometimes needs this field, you can add a bool parameter and then do something like this:
IQueryable<myEntity> results;
if (excludeBigData)
results = context.Database.SqlQuery<myEntity>("SELECT Field1, Field2, Field3, HugeField4 = NULL, Field5 FROM TableName").AsQueryable();
else
results = context.myEntity.AsQueryable();
If anyone manages to make the Linq extensions work properly like if it was the original EF object, please comment so I can update the answer.

I'm using here the anonymous type because otherwise you will get a
NotSupportedException: The entity or complex type 'ProjectName.File'
cannot be constructed in a LINQ to Entities query.
var file = context.Files
.Where(f => f.Id == idFile)
.FirstOrDefault() // You need to exeucte the query if you want to reuse the type
.Select(f => new {
f.Id, f.MimeType, f.Size, f.FileName, f.DataType,
f.DateModification, f.FileId
}).FirstOrDefault();
And also its not a bad practice to de-normalize the table into further, i.e one with metadata and one with payload to avoid projection. Projection would work, the only issue is, need to edit any time a new column is added to the table.

I tried this:
From the edmx diagram (EF 6), I clicked the column I wanted to hide from EF and on their properties you can set their getter and setter to private. That way, for me it works.
I return some data which includes a User reference, so I wanted to hide the Password field even though it's encrypted and salted, I just didn't want it on my json, and I didn't want to do a:
Select(col => new {})
because that's a pain to create and maintain, especially for big tables with a lot of relationships.
The downside with this method is that if you ever regenerate your model, you would need to modify their getter and setter again.

Using Entity Framework Power Tools you can do the following in efpt.config.json:
"Tables": [
{
"ExcludedColumns": [
"FileData"
],
"Name": "[dbo].[Attachment]",
"ObjectType": 0
}
]

Linq - how can I use a function in a query

I use C# on WP7 (Mango). I try to use a special query because I receive an error:
Method 'Int32 orderBirthday(System.DateTime)' has no supported
translation to SQL.
Yes, I know... Linq can't use my function but I don't know the right way...
I have a database table with the columns name and birthday. In my query I will calculate how many days are to the next birthday (from all items) and then I will order with "descending".
static int orderBirthday(DateTime Birthday)
{
DateTime today = DateTime.Today;
DateTime birthday = Birthday;
DateTime next = new DateTime(today.Year, birthday.Month, birthday.Day);
if (next < today)
next = next.AddYears(1);
int numDays = (next - today).Days;
// No Conversion
return numDays;
}
public void LoadCollectionsFromDatabase()
{
DateTime today = DateTime.Today;
var toDoItemsInDB = from ToDoItem todo in toDoDB.Items
let daysToBirthday = orderBirthday(todo.ItemDate)
orderby daysToBirthday ascending
select todo;
// Query the database and load all to-do items.
AllToDoItems = new ObservableCollection<ToDoItem>(toDoItemsInDB);
.
.
.
}

You either have to pull everything from the database and sort it locally (as Enigmativity) shows, or find a way to express the sort operation in a LINQ statement itself. And since you extracted the sorting behavior into its own function, you probably want to reuse this logic. In that case your best bet is to create a function that filters an IQueryable.
Here is an example of how to do this:
public static IOrderedQueryable<Item> OrderByBirthday(
this IQueryable<Item> items)
{
return
from item in items
let today = DateTime.Today
let birthday = item.ItemDate
let next = new DateTime(today.Year, birthday.Month, birthday.Day)
let next2 = next < today ? next.AddYears(1) : next
orderby (next - today).Days
select item;
}
You can use the method as follows:
var toDoItemsInDB = OrderByBirthday(toDoDB.Items);
Or you can use it as an extension method:
var toDoItemsInDB = toDoDB.Items.OrderByBirthday();

It's easy if you do this:
var toDoItemsInDB = from ToDoItem todo in toDoDB.Items.ToArray()
let daysToBirthday = orderBirthday(todo.ItemDate)
orderby daysToBirthday ascending
select todo.;
Notice the .ToArray() added to Items. You basically bring the results into memory and them your function can work.

Two ways:
One: Pull it from Linq2SQL to Linq2Objects using ToEnumerable(), and then use orderBirthday at the C# level.
Advantage is that it's simple to code and maintain, disadvantage is that it can be less efficient (depends on just what you are doing.
Two: Write an equivalent function in SQL, let's say it was called dbo.orderBirthday. Make your orderBirthday method a non-static method of your datacontext-derived class, and then mark your method as having a SQL function equivalent:
[Function(Name="dbo.orderBirthday",IsComposable=true)] //IsComposable is true for functions that can be used within queries, false for stored procedures that must be called on their own.
public int OrderBirthday([Parameter(Name="#birthday",DbType="datetime") DateTime birthday)
{
return Helper.OrderBirthday(birthday); // just to show that we can keep the static version around if we want and call into it. Alternatively we could just move the whole body here.
}
Here the C# code is used in a non-Linq2SQL context, and the SQL code is used in composing a SQL query in a Linq2SQL context.
Advantage: Can stay within SQL longer. Disadvantage: Two versions of the same method can fall out of sync and cause bugs.
It's also possible to have the C# code call the SQL code all the time:
[Function(Name="dbo.orderBirthday",IsComposable=true)]
public int OrderBirthday([Parameter(Name="#birthday",DbType="datetime") DateTime birthday)
{
return (int)ExecuteMethodCall(this, (MethodInfo)MethodInfo.GetCurrentMethod(), birthday).ReturnValue;
}
Advantage: Keeps one version (the SQL) as the only version, so it can't fall out of synch with the C# version. Disadvantage: Calls SQL even when working on objects that have nothing to do with SQL.

If you don't want to load all the items in memory and you want the database execute the calculation, you can write a stored procedure that can execute complex calculation and call the procedure using ADO or EF.

Entity Framework EdmFunction import is not recognized

First of all, I had a previous question some time before, which, although seems very similar, is NOT the same problem, have a look at it: Function import from SQL Server to Entity Framework runtime exception
This function, HammingDistance, used to work well after creating the scalar function in SQL Server, and then imported into the Entity Framework using the EDM function mapping. I kept building my site, made some differences around the site and the EDMX, but haven't touched the function and kept it safe. Here is the SQL function at the SQL Server:
ALTER function [dbo].[HammingDistance]
(#first bigint, #second bigint) returns int
as
begin
declare #xor bigint = #first ^ #second;
declare #one bigint = 1;
declare #diff int = 0;
declare #and bigint;
while (#xor != 0)
begin
set #and = #xor & #one;
if(#and = #one)
begin
set #diff = #diff + 1;
end
set #xor = #xor / 2;
end
return #diff;
end
And here is my C# code:
Declaration:
public static class EdmFunctionMapping
{
[EdmFunction("MainDB.Store", "HammingDistance")]
public static int GetHammingDistance(long hash1, long hash2)
{
throw new NotSupportedException("This method can only be used in a LINQ-to-Entities query");
}
}
Usage:
var query = (from p in VisibleObjects.OfType<Photo>()
let hd = EdmFunctionMapping.GetHammingDistance(targetPhoto.Analysis.Hash, p.Analysis.Hash)
let cd = Math.Abs(targetPhoto.Analysis.High.Red - p.Analysis.High.Red)+
Math.Abs(targetPhoto.Analysis.High.Green - p.Analysis.High.Green)+
Math.Abs(targetPhoto.Analysis.High.Blue - p.Analysis.High.Blue) +
Math.Abs(targetPhoto.Analysis.Low.Red - p.Analysis.Low.Red) +
Math.Abs(targetPhoto.Analysis.Low.Green - p.Analysis.Low.Green) +
Math.Abs(targetPhoto.Analysis.Low.Blue - p.Analysis.Low.Blue)
where
hd < 5 ||
(hd < 15 || cd < 100)
orderby hd ascending
select p).Take(50);
return query.ToList();
where VisibleObjects does not evaluate the Enumerable. Here it is anyway:
static IEnumerable<GlobalObject> VisibleObjects
{
get
{
return from obj in db.GlobalObjectSet where obj.IsVisible && !obj.SiteUser.IsDeactivated orderby obj.ID descending select obj;
}
}
Everything used to work about two or three weeks ago, and in that interval I've added/removed lots of things and did not check if Hamming Distance worked or not, so I can't tell anything about when it broke. It doesn't work anymore, it's just like EdmFunction attribute is not there, trying to evaluate in my application and throwing up the exception I wrote saying that it could only be used in an L2E query. I've double checked everything, even re-created the database completely and generated from EDMX, and created and imported the function using Update Model from Database, and it sees the function in EDMX, and it is available (obviously) in the EDMX file SSDL section such as:
<Function Name="HammingDistance" ReturnType="int" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="true" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo">
<Parameter Name="first" Type="bigint" Mode="In" />
<Parameter Name="second" Type="bigint" Mode="In" />
</Function>
But when it comes to the app, it just won't map to EDM! Tried several times, creating all the database from scratch, nothing changes, it throws the exception in query.ToList(), and there's no inner exception (it makes sense as it's throwing my own exception, which, should NOT be executed by the app). I have no idea of the source of the problem, am I missing something obvious?

If it doesn't recognize your Edm mapped function make sure that you didn't accidentally change the query to linq-to-objects somewhere because that is exactly the reason why you can see that error. To validate that, simply try to create another test query which will do just direct entity access and call your function. Something like:
long hash = targetPhoto.Analysis.Hash;
var query = from p in db.GlobalObjectSet.OfType<Photo>()
select new { EdmFunctionMapping.GetHammingDistance(hash, p.Analysis.Hash) };
If such query passes you have definitely problem I mentioned.
Edit:
I think I see the problem now. Your VisibleObjects returns IEnumerable => linq-to-objects. Try this instead:
public static IQueryable<GlobalObject> GetVisibleObjects(this IQueryable<GlobalObject> query)
{
return from obj in query
where obj.IsVisible &&
!obj.SiteUser.IsDeactivated
orderby obj.ID descending
select obj;
}
And call your method like:
from p in db.GlobalObjectSet.GetVisibleObjects().OfType<Photo>() ...

Calling user defined functions in Entity Framework 4

I have a user defined function in a SQL Server 2005 database which returns a bit. I would like to call this function via the Entity Framework. I have been searching around and haven't had much luck.
In LINQ to SQL this was obscenely easy, I would just add the function to the Data context Model, and I could call it like this.
bool result = FooContext.UserDefinedFunction(someParameter);
Using the Entity Framework, I have added the function to my Model and it appears under SomeModel.Store\Stored Procedures in the Model Browser.
The model has generated no code for the function, the XML for the .edmx file contains:
<Function Name="UserDefinedFunction" ReturnType="bit" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="true" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo">
<Parameter Name="someParameter" Type="int" Mode="In" />
</Function>
The closest I could get was something like this:
bool result = ObjectContext.ExecuteFunction<bool>(
"UserDefinedFunction",
new ObjectParameter("someParameter", someParameter)
).First();
But I got the following error message:
The FunctionImport
'UserDefinedFunction' could not be
found in the container 'FooEntities'.
Names have been changed to protect the innocent.
tldr: How do I call scalar valued user defined functions using Entity Framework 4.0?

I have finally worked it out :D For scalar functions you can append the FROM {1} clause.
bool result = FooContext.CreateQuery<bool>(
"SELECT VALUE FooModel.Store.UserDefinedFunction(#someParameter) FROM {1}",
new ObjectParameter("someParameter", someParameter)
).First();
This is definitely a case for using LINQ to SQL over EF.

If you want to call table-valued function in MS SQL via Entity Framework;
You can use this:
var retval = db.Database.SqlQuery<MyClass>(String.Format(#"select * from dbo.myDatabaseFunction({0})", id));

calling user defined static type SQL function
You can use ExecuteStoreQuery,
first parameter takes the SQL function calling statement in string format
second parameter takes an object of SqlParameter class in which you pass your function parameter name with its value. as shown in the below method
public string GetNumberOFWorkDays(Guid leaveID)
{
using (var ctx = new INTERNAL_IntranetDemoEntities())
{
return ctx.ExecuteStoreQuery<string>(
"SELECT [dbo].[fnCalculateNumberOFWorkDays](#leaveID)",
new SqlParameter { ParameterName = "leaveID", Value = leaveID }
).FirstOrDefault();
}
}

Calling a function in EF4 with ODPNET beta 2 (Oracle), which returns a NUMBER:
using (var db = new FooContext())
{
var queryText = "SELECT FooModel.Store.MY_FUNC(#param) FROM {1}"
var result = db.CreateQuery<DbDataRecord>(queryText,new ObjectParameter("param", paramvalue));
return result.First().GetDecimal(0);
}
I'm adding it here because based on Evil Pigeon's code I could figure it out for Oracle. (Also upvoted his answer).

ObjectResult result = context.ExecuteStoreQuery("select EmployeeName from User where Id = {0}", 15);
http://msdn.microsoft.com/en-us/library/ee358758.aspx

You might find this helpful. It would appear that you can only call them via eSQL directly and not using Linq.

thought id add a note for anybody else that come across this, if your sql function parameter is nullable you have to call the function in sql with parameter value of "default". To call a function like that using Entity Framwork try
bool result = FooContext.CreateQuery<bool>(
"SELECT VALUE FooModel.Store.UserDefinedFunction(null) FROM {1}"
).First();