Book "Johnson Glenn - Accessing Data with Microsoft .NET Framework 4 - 2011" contains example of custom function, and call of function:
gv.DataSource = (... select new { ... , ModelDefinedFunctions.Detail(..)});
But on CD in practice tests with that book:
var instructors = from p in context.People
where YearsSince((DateTime)p.HireDate) > 10
select p;
and explanation: You must refer to the custom function using the method name. The method name must not be qualified with the model name. The method requires a DateTime parameter and this must be included.
Don't have VS now, what is the right way?
ModelDefinedFunctions is the name of the class where the method Detail is defined. The two approaches are identical. There is no qualifier for the model name.
Related
I have two multi-word models, let's call them FunkyModel and AnotherModel.
Will creating a pivot table named another_model_funky_model work?
The docs and examples I've come across all use single word model names like this: model A - User, model B - Address, and pivot table will then be address_user.
If you dive into the source code of the BelongsToMany relation function, you'll find that if you haven't provided a $table, the code will execute the function joiningTable. This uses the current model and the passed related class, snake cases the names and then puts them in alphabetical order of each other.
Simply said, no matter if you have a single word or a couple, the result will always be the 2 classes snaked, in alphabetical order. Note that the alphabetical order is applied by the default php sort.
Examples:
Department + Occupation > department_occupation
AwesomeModel + LessInterestingModel > awesome_model_less_interesting_model
Role + UserPermission > role_user_permission
You can even try and see what the auto-generated name is by simply calling the following:
(new Model)->joiningTable(OtherModel::class, (new OtherModel));
Yes it would work, you can also name it whatever you want, you just need to declare the table name in the relation (same goes for the foreign keys)
class FunkyModel
{
public function anotherModels()
{
return $this->belongsToMany(AnotherModel::class, 'pivot_table_name', 'funky_model_id', 'another_model_id');
}
//list is IEnumeable NOT IEnumerable<T>
var IEnumerable<object> = list.AsQueryable().Cast<object>().Select(x=> .........);
object actually has a POCO underlying Anonymous class e.g
AccountId,Name,SecretInfo
What I want in the select statement is
AccountId = x.GetType().GetProperty("AccountId").GetValue(x,null),
Name = x.GetType().GetProperty("Name").GetValue(x,null)
Also I want to hide the SecretInfo Column which I can pass as a hardcoded string "SecretInfo"
Basically the select list needs to be built up dynamically on the Anonymous type....
How can this be done....Any Linq punters out there who can help me?
The answer to your question relies on anonymous types. The following code is what you can use:
var result = list.AsQueryable().Cast<Info>().Select(x => new
{
AccountId = x.AccountId,
Name = x.Name
});
Between the brackets that follow the new keyword in the select statement, you are creating an anonymous type that will have two implicitly typed read-only fields (AccountId and Name). Hope this helps!
I would like to post this quote from the linked (no pun intended) article:
Anonymous types typically are used in the select clause of a query expression to return a subset of the properties from each object in the source sequence. For more information about queries, see LINQ Query Expressions (C# Programming Guide).
I using Query DSL generated entity EntitySerializer in order to query JPA entities using QueryDSL (integrated with SpringData).
I’m receiving from the client property names and I want to create predicates for the properties that can be added (AND) to additional predicats.
I don’t know how to get from the EntitySerializer the predicate/Path that matches my property name. For example, let’s say we have a Person entity (with auto generated QPerson class) with a “name” property that I want to filter on (at the end I want to create a generic method). Here is the generic method:
Public Predicat getPredicatByPropertyName(String propertyName) {
QPerson p = QPerson.person;
person.getPredicat(“propertyName”).like(“tom”);
}
To create a String typed property just use the following snippet
new StringPath(p, propertyName)
which can then be used like this to create a Predicate instance
new StringPath(p, propertyName).like("tom")
I did it slightly different since as Timo said didn't work straightforward, here is it:
query.from(play);
query.where( Expressions.stringPath(play, "name").eq("New play") );
I know it could also be achieved by doing it separately:
StringPath column = Expressions.stringPath(play, "name");
query.from(play);
query.where( column.eq("New play") );
As of QueryDSL 5.0, I found two ways to do this independent of the column class:
First way: using just reflection:
Field pathField = p.getClass().getField(reportField.getFieldName());
ComparableExpressionBase<?> path = (ComparableExpressionBase<?>)
pathField.get(p);
Note: I use the ComparableExpressionBase class because it is extendend by all "path classes" that I found and it also can be used in select, orderBy and other functions to build the query
Second way: using reflection and ExpressionUtils:
Class<?> pParameterClass = (Class<?>) ((ParameterizedType) p.getClass().getGenericSuperclass())
.getActualTypeArguments()[0];
Class<?> pathClass = pParameterClass.getDeclaredField(pathName).getDeclaringClass();
Path<?> path = ExpressionUtils.path(pathClass, p, pathName);
Note: using this way we first get the class of the entity of the table see this answer for an explanation on how to get a parametrized type. Next, we get the class of the path and finally we get the path with the ExpressionUtils.path method.
I'm working on a custom linq extension for nHibernate by extending the BaseHqlGeneratorForMethod. The technique is documented here:
http://fabiomaulo.blogspot.com/2010/07/nhibernate-linq-provider-extension.html
I've had success with implementing these for various types of operations, but I must say - converting a simple linq expression to its full expression tree is not easy! I'm stuck on one now.
For this example, I have three entities. Employee, Group, and EmployeeGroup. The EmployeeGroup class sets up a many-to-many relationship between Employee and Group. I must specifically create the intermediate class because there are additional properties to track like specific permissions each employee has in each group. So there are two one-to-many relationships, rather than an nHibernate many-to-many relationship.
Now say I want to get all groups that contain a specific employee. I can write this query:
var groups = session.Query<Group>()
.Where(g => g.EmployeeGroups.Any(eg => eg.Employee == employee));
This works fine, but it's a lot to type. I'd much rather be able to do this:
var groups = session.Query<Group>().Where(g => g.HasEmployee(employee));
I start by creating an extension method like so:
public static bool HasEmployee(this Group group, Employee employee)
{
return group.EmployeeGroups.Any(eg => eg.Employee == employee);
}
This works when querying a local list of groups, but not against the nHibernate session. For that, I have to also create a linq extension and register it. Just like in the article (linked above), I create a GroupHasEmployeeGenerator class that extends BaseHqlGeneratorForMethod. I set its .SupportedMethods property to reference my HasEmployee extension method.
Where I get lost is in the override to BuildHql. The expression to build gets complicated pretty fast. I figure since I'm replacing the .Any clause - a good place to start is with the source for the built-in AnyHqlGenerator class. But that doesn't take into account that the source is a property of the original element, and it also doesn't take into account that I don't have a lambda expression to represent the where clause. I need to build these parts manually.
There's no point in posting my attempts so far, as they've all be quite far from anything that would work.
Will someone please help me convert this simple expression into the approprate set of methods for the BuildHql method override?
If there is any better documentation out there for this, please let me know. Thanks.
I know this question is a year old, but I ran into a very similar issue when implementing BaseHqlGeneratorForMethod today.
The input to BuildHql contains a collection of System.Linq.Expressions.Expression arguments that are passed to your extension method. Using these arguments, you can build an expression tree that represents the implementation of your extension method. If the resulting expression is something NHibernate.Linq supports, then you can transform that expression to a subtree of Hql using the provided IHqlExpressionVisitor.
In your example:
public static bool HasEmployee(this Group group, Employee employee)
{
return group.EmployeeGroups.Any(eg => eg.Employee == employee);
}
This would become something similar to this:
public override HqlTreeNode BuildHql(MethodInfo method, Expression targetObject, ReadOnlyCollection<Expression> arguments, HqlTreeBuilder treeBuilder, IHqlExpressionVisitor visitor)
{
var AnyMethod = EnumerableHelper.GetMethod("Any", new[] {typeof(IEnumerable<EmployeeGroup>), typeof(Func<EmployeeGroup, bool>)}, new[] {typeof(EmployeeGroup)});
var EmployeeGroupsProperty = ReflectionHelper.GetProperty<Group>(g => g.EmployeeGroups);
var EmployeeProperty = ReflectionHelper.GetProperty<EmployeeGroup>(eg => eg.Employee);
var EmployeeGroupParameter = Expression.Parameter(typeof(EmployeeGroup));
var EmployeeGroupPredicate = Expression.Lambda(Expression.Equal(Expression.MakeMemberAccess(EmployeeGroupParameter, EmployeeProperty), arguments[1]), EmployeeGroupParameter);
var CallExpression = Expression.Call(AnyMethod, Expression.MakeMemberAccess(arguments[0], EmployeeGroupsProperty), EmployeeGroupPredicate);
return visitor.Visit(CallExpression);
}
I can't really test this specific example, but the same approach worked for me when providing support for my own extension method.
I'm using a function :
fu_has_permissions(udt_person('johny','superman'),'fly_away')
udt_person is a user defined type :
create or replace TYPE udt_person AS OBJECT
(name VARCHAR2(3),
id VARCHAR2(18));
I want to use bind variables whan calling this function, but i'm not really sure what am i doing wrong ... Here's the code :
......
OracleParameter udtPersParam = new OracleParameter();
udtPersParam.ParameterName = ":pUdtPers";
udtPersParam.UdtTypeName = "UDT_PERS";
string[] paramValues = { name, id };
udtPersParam.Value = paramValues;
OracleParameter pAction = new OracleParameter(":pAction", OracleDbType.Varchar2, 255);
pAction.Value = action;
parameters.Add(udtPartParam);
parameters.Add(pAction);
try
{
_loginOdr = DBFacade.ExecuteSelectQuery("select fu_has_permissions(:pUdtPart, :pAction) from dual", parameters);
}
Thanks!
the udt type must be a class that implements
IOracleCustomType
and/or IOracleCustomTypeFactory, IOracleArrayTypeFactory
unfortuntately you cannot just create a string array and pass it in
look in the odp.net samples that come with the odp installation
%ora_home%\client_1\odp.net\samples\4\UDT
also check out these links for samples and walkthroughs
http://developergeeks.com/article/35/working-with-user-defined-type-oracle-udt-and-custom-type-using-odp-net-11g
http://www.codeproject.com/KB/database/ORACLE_UDT.aspx
and
http://st-curriculum.oracle.com/obe/db/hol08/dotnet/udt/udt_otn.htm
Don't know anything about ODP.Net really, but the error suggests that it doesn't like you trying to use a string array as the value for an Oracle parameter. Which doesn't sound unreasonable.
A quick google of 'odp.net object varchar2' gave this OTN forum post as the first result; it includes an example of using an object about half-way down, including converting to and from Oracle object types.
if I were you I'd have a look at the ODP add-in to Visual Studio. With this you can connect to your database, select a UDT on the database, and "Generate Custom Class" to get a .net class you can use.
Look inside the class and you'll see what Harrison means. Pay particular attention to the OracleObjectMappingAttributes on top of the properties, and the overrides of To/FromCustomObject.
When you construct your OracleCommand, the OracleParameter.Value needs to be a class of this type.
That should get you started at a high level. A word of warning, though. The code generated by ODP is ugly to say the least - we're on the point of ditching all ODP-generated classes in our own scenario. But you'll need to understand what things like IOracleCustomType, IOracleCustomTypeFactory, IOracleArrayTypeFactory, INullable are before you'll be in a position to do this.
Incidentally since your specific question surrounds arrays, you might want to look at Oracle NTYPEs here, rather than TYPEs.