i'm trying a 3d party tools Query Future | Entity Framework Plus[^] But i'm not sure if it's true what this tool claim to do ? The sql profiler it says : exec sp_executesql N'---EF+ Query Future 1 of 5....... .After there are 5 queries (I have 5 query that are executed with Future) But i don't know if these queries are executed in a single database hit ?

Are you Gerry Schmitz ?

I want to know if this software is telling the truth or no , if yes I want to use it.

Hello ! I'm using entity framework Is there any way to count how many database hit were made ? ( The reason why I make this question, is because i'm using a 3d party software that add some commands to Entity Framework. One of these is that several different queries (the software claim) are executed using a single database hit. I want to verify this.) Thank you !

Hello ! I'm using Entity Framework 6 with sql server 2008r2 database. I want to get from database only those records that have vl1>5.( i need to get from database only those objects that have vl1>5 and not to read all the objects and after to apply the condition ) I have 2 queries :

Dim query1 as IeQueryable(of myobj)= (From t in context.myobjs Where vl1<5).Tolist

Dim query2= (From t in context.myobjs.Asqueryable Where vl1<5).Tolist

Are these queries doing the same job that i want ?

ok , but Bindingsource.clear only remove items from bindingsource or also mark them for deletion from database ?

I've tried also Bindingsource.Clear

Bindingsource.Clear

Bindingsource.Clear , this is working , but does this remove also from database ( if I call savechanges for example ?)

Hello ! I'm using vb.net 2017 and EF 6. I have a bindingsource and also datagrid that is bound to this bindingsource. I need a way to clear all the items from bindingsource to empty it , but without deleting from database. I've tried

Bindingsource1.Datasource=Nothing.

But , after calling this , the datagrid still have all the bindingsource items.

Hello ! I'm using vb.net 2017 and Entity Framework 6. Is there any way to update only one table in model from database ? I try to right click on model.edmx and choose Update model from database , but this way update and recreate the entire model. I've tried also to delete only the table that I've changed on database , and after I choose Update model from database and after on ADD I select only this table , but after the entire model is recreated. How can I do ?

I mean better for performance and the complexity of sql query that is generated in each case..

I've found 2 solutions that are working. Can someone tell me which is better ? Solution 1

Dim lst = (From t In context.MasterTable.Where(Function(t1) t1.id = 7)
Select New With {
t,
.chld1 = t.child1s.Where(Function(t21) t21.vl1 >5),
.chld2 = t.child2s.Where(Function(t31) t31.vl2>6 ),
.chld3 = t.child3s.Where(Function(t41) t41.vl3>7),
.chld3itms = t.child3s.Where(Function(t51) t51.vl3>7).Select(Function(t511) t511.Child3Itms)
}).ToList

Solution 2

Dim lst = (From t In context.MasterTable.Where(Function(t1) t1.id = 7)
Select New With {
t,
.chld1 = t.child1s.Where(Function(t21) t21.vl1 >5),
.chld2 = t.child2s.Where(Function(t31) t31.vl2>6 ),
.chld3 = (From t2 in t.child3s.Where(Function(t41) t41.vl3>7)
Select New With {
t2,
.chld3it=t2.Child3Itms
})
}).ToList

Now i'm getting an error :

System.NotSupportedException: 'LINQ to Entities does not recognize the method 'System.Linq.IQueryable`1[Myprog.Child3] Include[child3,ICollection`1](System.Linq.IQueryable`1[Myprog.Child3], System.Linq.Expressions.Expression`1[System.Func`2[Myprog.Child3,System.Collections.Generic.ICollection`1[Myprog.Child3itm]]])' method, and this method cannot be translated into a store expression.'

I'm using entity Framework 6. On my database I have these tables :

MasterTable ( Id , name)
Child1 ( ID , name , vl1 , Master_ID)
Child2 ( ID , name , vl2 , MasterID )
Child3 (ID , name , vl3 , Master_ID )
Child3Itm ( ID , name , Child3_ID)

For a given `MasterTable` item, I want to load with a single Query from database:

• All `Child1` where `vl1 > 5`
• All `Child2` where `vl2 > 6`
• All `Child3` where `vl3 > 7`

And in each `Child3` to load all of the `Child3Itm` content.

I'm using this query:

Dim lst = (From t In context.MasterTable.Where(Function(t1) t1.id = 7)
Select New With {
t,
.chld1 = t.child1s.Where(Function(t21) t21.vl1 >5),
.chld2 = t.child2s.Where(Function(t31) t31.vl2>6 ),
.chld3 = t.child3s.Where(Function(t41) t41.vl3>7).Select(Function(t411) t411.Child3Itms)
}).ToList

The problem is that no `Child3` are selected. All others are OK. What can i do? Thanks in advance!

Hello ! I have 2 classes Books and Author. On of members of Books is of type Author. On Class Books I want to have a Constructor that takes all the parametres for book and for author : This is my code :

class author
{

private :
string name;
string email;

public :
string get_name(){return name;}
string get_email(){return email;}

void  set\_name(string name){this->name=name;}
void set\_email(string email){this->email=email;}


author(string name,string email)

{   this->name=name;

    this->email=email;

}

}

class book
{
private :
string title;
int year;
author auth;

public:

string get\_title(){return title;}
int get\_year(){return year;}


void  set\_title(string title){this->title=title;}
void set\_year(float year){this->year=year;}

book(string title, int year):author(string name,string email)
{
   this->title=title;
   this->year=year;
  ???????
}

}

I don't know how can i change the constructor of book in order that it takes all the perameter for book and for the author? Thank you !

Again , on Local Cache I have all the students.The same problem as my query on my first post.

ok , but what's wrong with my query , and what should I do ?

I have used LastOrDefault in other cases , and there were no problems translating in SQL Query. so I think there is a SQL equivalent for LastOrDefault.

I've tried your solutions , and both produced the same error :

LINQ to Entities does not recognize the method 'Program1.status LastOrDefault[status](System.Collections.Generic.IEnumerable`1[Program1.status])' method, and this method cannot be translated into a store expression.'

Hello ! I'm using vb.net 2017 and Entity Framework 6 with sql server 2008r2. I have 2 tables in database : Studnets: (ID , Name ) Status : (ID , Year , Student_ID , Active ) The table status has the status of students in a specific year. A student may have 0 or 1 status on a year . ( If a student has not a status on a year , the last status from previous years ( if exists ) is used as a status for it this year) Now I want to have a query that load on local cache only the students that are active on a specific year. This is my query :

Dim queryv As IEnumerable(Of students)
queryv = (From t1 In context.students order by t.Name select t)
queryv = (From t1 In queryv
Let p = t1.status.Where(Function(t2) t2.year<=year1).OrderBy(Function(t3) t3.year).LastOrDefault
Where Not IsNothing(p) AndAlso p.active = True
Select t1)
queryv.Tolist

On Database there are 2 students , one of them has an Active status this year , the other has a non-active status. The problem is that after i excute that query , i have 2 instructions , just for testing :

Messagebox.show(queryv.count)
MessageBox.show(context.studnets.local.Count)

The results are : 1 (for queryv) 2 (for local cache ) On Local cache both students exists. Why is this result ? Thank you !

Then , really I don't understand why a such method does not exist on DBContext directly but I should use objectContext. Because the option StoreWins means that the local cache will be overwritten with new data on my database , we have discussed this on our conversation.