Visual Basic

12-Jan-15 6:31

I'm working with vb.net and entity framework.

In my form , I have 2 comboboxes : Article and price. ( For both comboboxes , .Selectedvalue is an integer )

If I use this expression :

SQL

Dim gj As IEnumerable(Of Myobject)
 gj = (From t In context.myobjects Where t.art = Article.SelectedValue And t.prc = price.SelectedValue
       Select t).ToList

an error is produced :

An unhandled exception of type 'System.NotSupportedException' occurred in EntityFramework.SqlServer.dllAdditional information: LINQ to Entities does not recognize the method 'System.Object CompareObjectEqual(System.Object, System.Object, Boolean)' method, and this method cannot be translated into a store expression.

If I use this code :

Dim a as integer=Article.SelectedValue
 Dim c as integer= price.selectedvalue
 Dim gj As IEnumerable(Of Myobject)
 gj = (From t In context.myobjects Where t.art = a And t.prc = c
       Select t).ToList

everything is OK.

What I have wrong in first expression , and how should I modify to make it work , because I don't want to use extra variables like in the second code.

Thank you !

Richard Deeming12-Jan-15 6:56

Richard Deeming

12-Jan-15 6:56

Does it work if you wrap a CInt around the SelectedValue?

VB.NET

Where t.art = CInt(Article.SelectedValue) And t.prc = CInt(price.SelectedValue)

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

dilkonika12-Jan-15 7:12

12-Jan-15 7:12

It's the same situation.
Doesn't work.

ZurdoDev12-Jan-15 7:23

12-Jan-15 7:23

SelectedValue is an object, http://msdn.microsoft.com/en-us/library/system.windows.controls.primitives.selector.selectedvalue(v=vs.110).aspx[^] and the error says it does not recognize "System.Object CompareObjectEqual(System.Object, System.Object, Boolean)" meaning you can't do what you're doing on Objects.

Assuming you have simple strings in your combobox then all you likely need to do is call .ToString() on the SelectedValue.

There are only 10 types of people in the world, those who understand binary and those who don't.

dilkonika12-Jan-15 7:32

12-Jan-15 7:32

If .selectedvalue is an object , then why the expression used in second code are ok :

Dim a as integer=Article.SelectedValue

I think this is the same as :
....

...Where t.art = Article.SelectedValue

What's the difference ?

ZurdoDev12-Jan-15 7:38

12-Jan-15 7:38

I believe VB will do implicit conversions. I don't think C# would allow that.

There are only 10 types of people in the world, those who understand binary and those who don't.

dilkonika12-Jan-15 7:50

12-Jan-15 7:50

Who's talking about C# ? All the codes are in VB.net.

ZurdoDev12-Jan-15 7:52

12-Jan-15 7:52

Yes, I said that VB allows you to do that. I was simply pointing out that the way you have it written won't work in C#. In other words, VB is doing stuff behind the scenes.

There are only 10 types of people in the world, those who understand binary and those who don't.

dilkonika12-Jan-15 16:48

12-Jan-15 16:48

ok but is there any solution ?

ZurdoDev13-Jan-15 1:34

13-Jan-15 1:34

dilkonika wrote:
ok but is there any solution ?

As I pointed out the first time I responded, call .ToString().
http://www.codeproject.com/Messages/4978387/Re-Why-this-expression-produce-error.aspx[^]

There are only 10 types of people in the world, those who understand binary and those who don't.

dilkonika13-Jan-15 4:19

13-Jan-15 4:19

Hello !
Calling the ToString method , make this expression works.
But I want to know that is this correct , because inside the query , variables of different types are compared ( integer with string ).
Can this modified expression produce a correct result every time ?
Thank you !

ZurdoDev13-Jan-15 4:21

13-Jan-15 4:21

You could convert to integer instead, you don't have to do to string.

There are only 10 types of people in the world, those who understand binary and those who don't.

dilkonika13-Jan-15 4:29

13-Jan-15 4:29

but , as I have posted before , using the Cint doesn't work and produce the same error.

ZurdoDev13-Jan-15 4:32

13-Jan-15 4:32

I think you're spending too much time on this. The original problem is you can't use objects the way you were doing. So, convert it to something that works and move on.

However, all you said was CInt did not work. What was the error? It would have been a different error. And perhaps use Convert.ToInt32() instead of CInt which is old VB code anyway and not .Net.

There are only 10 types of people in the world, those who understand binary and those who don't.

dilkonika13-Jan-15 5:00