Calling User Defined Function in Linq to SQL partial class

[messalux]

Hello,
I've already used User Defined Stored Procedures calls with different definitions in a partial Linq to Sql class to use procedure overloading in .net and it's working very fine.
I've tried to do the same thing with a User Define Function, no compiling errors but it execution (function age(namd) ) threads an exception "An insufficient number of arguments were supplied for the procedure or function age"

Here what I wrote in the partial class datacontext

<FunctionAttribute(Name:="dbo.Age", IsComposable:=True)> _
    Public Function Age(<Parameter(DbType:="BigInt")> ByVal nadm As System.Nullable(Of Long)) As String
        Return CType(Me.ExecuteMethodCall(Me, CType(MethodInfo.GetCurrentMethod, MethodInfo), nadm).ReturnValue, String)
    End Function

And here is the function definition in the Linq file (.designer.vb)

<FunctionAttribute(Name:="dbo.Age", IsComposable:=true)>  _

            Public Function Age(<Parameter(DbType:="BigInt")> ByVal nadm As System.Nullable(Of Long), 
                                                            <Parameter(Name:="TypeAge", DbType:="TinyInt")> ByVal typeAge As System.Nullable(Of Byte)) 
                                                            As String
                        Return CType(Me.ExecuteMethodCall(Me, CType(MethodInfo.GetCurrentMethod,MethodInfo), nadm, typeAge).ReturnValue,String)
            End Function

Could anyone help me?
Thanks