New Posts New Posts RSS Feed: Variable Linq
  FAQ FAQ  Forum Search   Calendar   Register Register  Login Login

Variable Linq
 Post Reply Post Reply
Author
  Share Topic Share Topic  Topic Search Topic Search  Topic Options Topic Options
jolemaiavix View Drop Down
Newbie
Newbie


Joined: 26-Oct-2010
Posts: 5 		Post Options Post Options   Quote jolemaiavix Quote  Post ReplyReply Direct Link To This Post Topic: Variable Linq
    Posted: 26-Oct-2010 at 12:20pm
I need to run the linq below:

IEntityQuery<Employee> qry = (IEntityQuery<Employee>)_entityManager.BasePersons
                .Include(Employee.PathFor(b => b.Address))
                .Include(Employee.PathFor(b => b.Address.Country))
                .Where(b => b.Name.Contains(pValue));

Being that I need to replace the code "Where (b => b.Name.Contains (pvalue))" for "Where (MyVariable)". MyVariable will contain "Name == 'test'." Is it possible? How do I?
Back to Top
sbelini View Drop Down
IdeaBlade
IdeaBlade
Avatar

Joined: 13-Aug-2010
Location: Oakland
Posts: 786 		Post Options Post Options   Quote sbelini Quote  Post ReplyReply Direct Link To This Post Posted: 26-Oct-2010 at 2:34pm
Hi jolemaiavix,
 
You can build queries dynamically by using the Predicatebuilder.
In your case you will parse your MyVariable string and build the query according with the string. (i.e. "Name == 'test'" or Name.Contains("test") )
 
You can find detailed information about PredicateBuilder in our API documentation (available online and with your DevForce installation).


Edited by sbelini - 26-Oct-2010 at 2:40pm
Back to Top
jolemaiavix View Drop Down
Newbie
Newbie


Joined: 26-Oct-2010
Posts: 5 		Post Options Post Options   Quote jolemaiavix Quote  Post ReplyReply Direct Link To This Post Posted: 28-Oct-2010 at 4:57am
I can not use "contains". The contents of MyVariable will be filled on a selection by an end user. The content of it can be "Name == 'test'" or "Type == 2" or anything else.
Back to Top
sbelini View Drop Down
IdeaBlade
IdeaBlade
Avatar

Joined: 13-Aug-2010
Location: Oakland
Posts: 786 		Post Options Post Options   Quote sbelini Quote  Post ReplyReply Direct Link To This Post Posted: 28-Oct-2010 at 12:30pm
Hi,
 
I mentioned the "contains" example because you had it initially in your snippet.
Yet, the PredicateBuilder is what you are looking for.
 
Suppose MyVariable is "Name == 'test'":
 
  var MyVariable = "Name == 'test'";
  var strings = MaVariable.Split(' ');
  var expr1 = PredicateBuilder.Make(typeof(Employee), strings[0].Trim()
    ,FilterOperator.IsEqualTo
    ,Int32.Parse(strings[2].Trim('\'')));
  var exprFunc = (Expression<Func<Employee, bool>>)expr1.ToLambdaExpression();
  var query = mgr.Employees.Where(exprFunc);
  var results = query.Execute();
 
 
I hope it helps


Edited by sbelini - 28-Oct-2010 at 12:30pm
Back to Top
jolemaiavix View Drop Down
Newbie
Newbie


Joined: 26-Oct-2010
Posts: 5 		Post Options Post Options   Quote jolemaiavix Quote  Post ReplyReply Direct Link To This Post Posted: 29-Oct-2010 at 5:57am
which namespaces need?
Back to Top
sbelini View Drop Down
IdeaBlade
IdeaBlade
Avatar

Joined: 13-Aug-2010
Location: Oakland
Posts: 786 		Post Options Post Options   Quote sbelini Quote  Post ReplyReply Direct Link To This Post Posted: 29-Oct-2010 at 9:13am
IdeaBlade.Linq
 
You can find aditional information about PredicateBuilder at the API Documentation available online and installed with DevForce2010.
Back to Top
jolemaiavix View Drop Down
Newbie
Newbie


Joined: 26-Oct-2010
Posts: 5 		Post Options Post Options   Quote jolemaiavix Quote  Post ReplyReply Direct Link To This Post Posted: 29-Oct-2010 at 9:49am
The code looks like this:

    public override void Inicializar(string texto)
    {
      ListaRegistros = new ObservableCollection<T>();
      ListaRegistros.CollectionChanged += ListaRegistros_CollectionChanged;

      _propriedadeDinamicaBusy = _propriedadeIsBusyMaster;

      AthenasEntityManager.Fetching += (s, e) =>
      {
        IsBusy = true;
      };

      AthenasEntityManager.Queried += (s, e) =>
      {
        IsBusy = false;
        _propriedadeDinamicaBusy = _propriedadeIsBusyDetail;
      };

      Entity instancia = (Entity)Activator.CreateInstance(typeof(T));

      var MyVariable = texto;
      var strings = MyVariable.Split(' ');
      var expr1 = PredicateBuilder.Make(typeof(T), strings[0].Trim()
        , FilterOperator.IsEqualTo
        , Int32.Parse(strings[2].Trim('\'')));
      var exprFunc = (Expression<Func<T, bool>>)expr1.ToLambdaExpression();

      var query = new EntityQuery<T>(instancia.EntityAspect.EntitySetName, AthenasEntityManager).Where(exprFunc);

      query.ExecuteAsync(
        args =>
        {
          if (!Excecao.TratarRetornoCallback(args))
            return;

          args.Results.ForEach(ListaRegistros.Add);

          RegistroCorrenteLocal = ListaRegistros.FirstOrDefault();

          if (AoCarregarRegistros != null)
          {
            AoCarregarRegistros(this, new EventArgs());
          }
        });

      //var teste = ListaRegistros.Where<string>("","");
    }

Type T is inherited in the call to "ViewModelCadastro.Inicializar("codigo == 1");".

      TipoDominioType = Util.GetAssemblyType("Dominio." + TipoDominio);
      if (TipoDominioType == null)
      {
        Excecao.ExibirMensagem(string.Format("Não foi possível encontrar o domínio {0}.", TipoDominio));
        return;
      }

      ViewModelCadastro = (Activator.CreateInstance(typeof(ViewModel<>).MakeGenericType(new Type[] { TipoDominioType })) as IViewModel);
      if (ViewModelCadastro == null)
      {
        return;
      }
      ViewModelCadastro.Inicializar("codigo == 1");

The red line is returning null to exprFunc. Where's the error?
Back to Top
sbelini View Drop Down
IdeaBlade
IdeaBlade
Avatar

Joined: 13-Aug-2010
Location: Oakland
Posts: 786 		Post Options Post Options   Quote sbelini Quote  Post ReplyReply Direct Link To This Post Posted: 29-Oct-2010 at 10:48am
I couldn't reproduce the issue here.
Was expr1 created properly?
 
Here's a testunit against NorthwindIB which executed with no issues:
 
[TestMethod]
public void TestPredicateBuilder2() {
  var mgr = new NorthwindIBEntityManager();
  mgr.AuthorizedThreadId = null;
  //var MyVariable = "EmployeeID == 1";
  var MyVariable = "LastName == 'Davolio'";
  var strings = MyVariable.Split(' ');
  var expr1 = PredicateBuilder.Make(typeof(Employee), strings[0].Trim()
    , FilterOperator.IsEqualTo
    , strings[2].Trim('\''));
  var exprFunc = (Expression<Func<Employee, bool>>)expr1.ToLambdaExpression();
  Entity instancia = (Entity)Activator.CreateInstance(typeof(Employee));
  var query = new EntityQuery<Employee>(instancia.EntityAspect.EntitySetName, mgr).Where(exprFunc);
  var emps = query.Execute();
}
 
 
I suggest you create a simple test, and gradually add complexity to it, so you can isolate what's causing the issue.


Edited by sbelini - 29-Oct-2010 at 10:51am
Back to Top
jolemaiavix View Drop Down
Newbie
Newbie


Joined: 26-Oct-2010
Posts: 5 		Post Options Post Options   Quote jolemaiavix Quote  Post ReplyReply Direct Link To This Post Posted: 08-Nov-2010 at 4:47am
worked perfectly! Another question: how would for the "ORDER BY" also be dynamic as the WHERE?
Back to Top
sbelini View Drop Down
IdeaBlade
IdeaBlade
Avatar

Joined: 13-Aug-2010
Location: Oakland
Posts: 786 		Post Options Post Options   Quote sbelini Quote  Post ReplyReply Direct Link To This Post Posted: 15-Nov-2010 at 9:24am
Hi jolemaiavix,
 
Unfortunatelly, using OrderBy dynamically is not possible yet, but we have it in our list of features to be implemented.
 
sbelini.
Back to Top
gkneo View Drop Down
Newbie
Newbie
Avatar

Joined: 23-Jun-2010
Posts: 21 		Post Options Post Options   Quote gkneo Quote  Post ReplyReply Direct Link To This Post Posted: 02-Dec-2010 at 1:50am
Hi, jolemaiavix.

Why don't you try the following:

   foreach (var fieldName in _orderFields)
                {
                    Type t = _filterEntity.EntityAspect.GetDataProperty(fieldName).DataType;
                    if (t == typeof(String))
                        query = query.OrderBy(GetMember<Employee, string>(_filterEntity, fieldName));
                    else if (t == typeof(Int32))
                        query = query.OrderBy(GetMember<Employee, Int32>(_filterEntity, fieldName));
                }



and the GetMember method:
 public static System.Linq.Expressions.Expression<Func<T, T2>> GetMember<T, T2>(T entity, string memberName)
        {
            System.Linq.Expressions.ParameterExpression pe =
                System.Linq.Expressions.Expression.Parameter(typeof(T), "p");
            return (System.Linq.Expressions.Expression<Func<T, T2>>)
                System.Linq.Expressions.Expression.Lambda(typeof(Func<T, T2>),
                    System.Linq.Expressions.Expression.Property(pe, memberName), pe);
        }

_filterEntity is a dummy instance (in this case of type Employee) used to retrieve information about the queried type.  (I think may be another way to do this without using a dummy instance).  

_orderFields is a list of string which values are the name of the fields to use in the "order by" clause.

query is a IEntityQuery<Employee>

Guillermo
Back to Top
 Post Reply Post Reply

Forum Jump Forum Permissions View Drop Down