Calling SQL scalar function from Linq Query - sql

Question

There are many similar threads here, but none of them can't solve my problem.
As far as I know, there are two methods for calling SQL scalar function from linq.
1. method:
I've added my function to .edmx file using XML editor and my function is:
<Function Name="prisustvoPostotci" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo">
<CommandText>
select dbo.prisustvoPostotci(#matica_ID,#godina)
</CommandText>
<Parameter Name="matica_ID" Type="int" Mode="In" />
<Parameter Name="godina" Type="int" Mode="In" />
</Function>
I went to model browser and double clicked on my function in Function Imports and changed return collection type to Int32. My function is returning integer.
Now I can call my function from linq using:
using (DB_Entities dm = new DB_Entities())
{
dm.prisustvoPostotci(1, 2016).FirstOrDefault();
}
It returns valid integer value!
But if I call my function from Linq Query like this:
query = query.Where(x => x.date.Value.Year == max_year &&
dm.prisustvoPostotci(x.ID, max_year).FirstOrDefault() >= 50);
It throws this error:
LINQ to Entities does not recognize the method
'System.Data.Entity.Core.Objects.ObjectResult1[System.Nullable1[System.Int32]]
prisustvoPostotci(System.Nullable1[System.Int32],
System.Nullable1[System.Int32])' method, and this method cannot be
translated into a store expression.
2. method:
I've added my function to .edmx file using XML editor and my function is:
<Function Name="prisustvoPostotci" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo">
<CommandText>
select dbo.prisustvoPostotci(#matica_ID,#godina)
</CommandText>
<Parameter Name="matica_ID" Type="int" Mode="In" />
<Parameter Name="godina" Type="int" Mode="In" />
</Function>
I went to model browser and double clicked on my function in Function Imports and changed return collection type to Int32. My function is returning integer.
Then I created a partial class and wrote this method:
public static class EntityFunctions
{
[EdmFunction("Model.Store", "prisustvoPostotci")]
public static int prisustvoPostotci(int matica_ID, int godina)
{
throw new NotSupportedException("Direct calls not supported");
}
}
"Model.Store" is the correct name of my Model Store read from my Schema Namespace inside .edmx file.
Now, if I call my function from linq using:
EntityFunctions.prisustvoPostotci(119, 2016).ToString()
It throws this error:
throw new NotSupportedException("Direct calls not supported");
Also, if I call my function from Linq Query like this:
query = query.Where(x => x.date.Value.Year == max_year &&
EntityFunctions.prisustvoPostotci(x.ID, max_year) >= 50);
It throws this error:
The function or function import 'Model.Store.prisustvoPostotci' is not composable. A non-composable function or function import cannot be called in a query expression.
I tried to edit my .edmx file and change a property IsComposable="true", but it gives me this error:
Functions declaring command text cannot be composed.
Can You help me solve this problem!?
Many thanks in advance !!
::cheers::
Josip

Answer 1

Thanks to Gerd Arnold I realize that scalar functions cannot be used inside query where statement.
Here is how I managed to filter my query by calling scalar function outside query:
var result = query.ToList();
for (int i = 0; i < result.Count; i++)
{
// prisustvoPostotci(ID, year) is my scalar function
if (dm.prisustvoPostotci(result[i].ID, max_year).FirstOrDefault() >= 50)
{
result.Remove(result[i]);
i--;
}
}
This way calling scalar function will work and we can remove matching records from the result!
Hope this will help someone.
:: cheers ::
Josip