Get the primary key property name and the Foreign key property name of an arbitrary entity - Visual Basic Discussion Boards

Yes, it is. It's just not the answer you want.

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Dave Kreskowiak

Hi all.
I want to detect keys events only from a phisical keyboard in VB6,don't respond a virtual keyboard's.How can I do it?
Thank you.

First off, VB6 is long since dead. You really have no reason to be doing new development work in it as Visual Studio 2013 Express is FREE!

Next, it depends on how the virtual keyboard is stuffing keystrokes and what your application is doing. It may come down to you implementing a global keyboard hook, but this may not work depending on the virtual keyboard.

You may not have any way to figure out the difference.

The question is why would you want to?

A guide to posting questions on CodeProject

Click this: Asking questions is a skill.
Seriously, do it.

Dave Kreskowiak

Thank you Dave Kreskowiak.
Maybe I must go into Visual Studio 2013 Express tomorrow.But I only want to realize this with VB6 now,not a more advanced version.It's said with the scanCode of tagKBDLLHOOKSTRUCT,even with the other members in this structure,we can discriminate them.If the soft keyboard neglected it.Any adivse is welcome.
Thank you again.

Like Dave recommended to you, drop VB6. Pick up VB.NET or C#.

For the keyboard issue, this article might be of help: Using Raw Input from C# to handle multiple keyboards[^]

It's in C#. If you go with VB.NET you could just use it as a referenced DLL. Or maybe use some code-translator[^] to translate it into VB.NET.

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

Hi, Sascha Lefévre.
I have searched the information about Raw Input in your link and MSDN.It's a good suggestion.I will take some days to get it.
Thanks for your help.

I have a bindingsource bound to an entity.

When the bindingsource has at least one item , I can get the item's data type with :

MyBindingSource.Current.GetType

But how can I do in the case when bindingsource has no items ?

I try this :

MyBindingSource.GetItemProperties(Nothing)(0).ComponentType

But doesn't work.

Thank you !

modified 17-Apr-15 12:15pm.

Hello !
I'm using entity Framework (Database First ) with a SQL Server Database.
I have a situation where I have an object ( that is an entity object ) , but the type is known only on runtime ).

I need to get the Primary key property name and the Foreign key property name ( for a specific relation)

for example
MyObj (ObId , name , val1)------- ( ObID is primary key )
MyChild (ChlID ,dt , MyObj_ID) --- ( CHLID is primary Key , Myobj_ID is foreign key)

Dim obj1
.....
Get_PK(obj1)
I want that the possible function Get_PK to return a string with the value :
- "ObID" ( if the type of the object is MyOBJ) , or "ChlID" if the object is of the type MyChild.

and the function Get_Parent(obj1,chl1) to return "MyOBj_ID"

But of course it must be a general function that works with every class inside the entity.

Actually I have 2 functions :

Public Function Get_pk(ctx As MyEntities, entity As Object) As String
        Dim objectContext = DirectCast(ctx, System.Data.Entity.Infrastructure.IObjectContextAdapter).ObjectContext
        Dim t As Type = entity.GetType.BaseType
        Dim m As MethodInfo = objectContext.GetType().GetMethod("CreateObjectSet", New Type() {})
        Dim generic As MethodInfo = m.MakeGenericMethod(t)
        Dim st As Object = generic.Invoke(objectContext, Nothing)
        Dim entitySetPI As PropertyInfo = st.GetType().GetProperty("EntitySet")
        Dim entitySet As Metadata.Edm.EntitySet = DirectCast(entitySetPI.GetValue(st, Nothing), Metadata.Edm.EntitySet)
        Dim keyNames As IEnumerable(Of String) = entitySet.ElementType.KeyMembers.Select(Function(k) k.Name)
        Return keyNames(0)
    End Function

This is for Primary Key property , and is working , but is is slow ( I'm thinking if Entity framework has a built in method to get this directly ??? )

Public Function Get_FK(ctx As MyEntities, entity As Object, parenttable As String) As String
      Dim fk = entity.MetadataWorkspace.GetItems(Of Metadata.Edm.AssociationType)(Metadata.Edm.DataSpace.CSpace).Where(Function(a) a.IsForeignKey)
      Dim fkname = fk.Where(Function(x) x.ReferentialConstraints(0).ToRole.Name = parenttable)
      Dim refcol = fkname.Select(Function(x) x.ReferentialConstraints(0).FromProperties(0).Name).First()
      return refcol
  End Function

This is for the foreign key (related with a parenttable that is passed as parameter ). This is not working. I get an error in the first line because entity is a proxy object and MetaDataWorkspace is not a member of proxy types. and I don't know if this function works at all.

What can I do ?

Thank you !

modified 17-Apr-15 12:15pm.

For the Primary key :

Public Function Get_PK(ctx As MyEntities, entity As Object) As String
    Dim objectContext = DirectCast(ctx, System.Data.Entity.Infrastructure.IObjectContextAdapter).ObjectContext
    Dim t As Type = entity.GetType.BaseType 
    Dim m As MethodInfo = objectContext.GetType().GetMethod("CreateObjectSet", New Type() {})
    Dim generic As MethodInfo = m.MakeGenericMethod(t)
    Dim st As Object = generic.Invoke(objectContext, Nothing)
    Dim entitySetPI As PropertyInfo = st.GetType().GetProperty("EntitySet")
    Dim entitySet As Metadata.Edm.EntitySet = DirectCast(entitySetPI.GetValue(st, Nothing), Metadata.Edm.EntitySet)
    Dim keyNames As IEnumerable(Of String) = entitySet.ElementType.KeyMembers.[Select](Function(k) k.Name)
    Return keyNames(0)
End Function

For the Foreign key :

Public Function Get_FK(ctx As MyEntities, entity As Object, parenttable As String) As String
    Dim objectCont = DirectCast(ctx, System.Data.Entity.Infrastructure.IObjectContextAdapter).ObjectContext
    Dim t As Type = entity.GetType.BaseType
    Dim m As MethodInfo = objcont.GetType().GetMethod("CreateObjectSet", New Type() {})
    Dim generic As MethodInfo = m.MakeGenericMethod(t)
    Dim st As Object = generic.Invoke(objcont, Nothing)
    Dim entitySetPI As PropertyInfo = st.GetType().GetProperty("EntitySet")
    Dim entitySet As Metadata.Edm.EntitySet = DirectCast(entitySetPI.GetValue(st, Nothing), Metadata.Edm.EntitySet)
    Dim elementtype = entitySet.ElementType
    Dim entitymember = elementtype.NavigationProperties.Where(Function(t1) t1.ToEndMember.Name = parenttable)
    Return entitymember.First.GetDependentProperties.First.Name
End Function

Please give me some reputation , because I found the answer Poke tongue | ;-P

In an existing vb.net 2010 application, I want to sum the values contained in column # 5 in a collection called _dt.

The following is the code for how the specific column is accesed when it is to be displayed on the internet :

Dim _dt As DataTable = New DataTable
   For i = 0 To _dt.Rows.Count() - 1
         _htmlTable.Append("Total # parts: " + _dt.Rows(i)(_dt.Columns(5).ColumnName()).ToString() + "   ")
         _htmlTable.Append("<BR />")
   Next

I basically want a total value for this specific column. Can you show me the code of how I can sum the value that is contained in column #5 of the code that I listed above?

1) Declare a variable outside your for-loop that has the same type as that column.
2) Inside the for-loop add the value that you already display as string to that variable.
3) After the for-loop append the value of that sum-variable to your StringBuilder.

Unrelated:
Exactly like you access the column in the column-collection of the table by its index:

VB

_dt.Columns(5)

..you can access the column of a row by its index. So your detour via the column-name is completely unneccessary. Instead of:

VB

_dt.Rows(i)(_dt.Columns(5).ColumnName()).ToString()

..you can write:

VB

_dt.Rows(i)(5).ToString()

And: You already use the StringBuilder - then you could use it also to replace the string-concatenation here:

VB

_htmlTable.Append("Total # parts: " + _dt.Rows(i)(5).ToString() + "   ")

..like so:

VB

_htmlTable.Append("Total # parts: ").Append(_dt.Rows(i)(5).ToString()).Append("   ")

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

Thanks! That helped alo!

You're welcome!

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

Hello !
It's possible to create a list of unknown type at compile time ?
Let's suppose the type is in one variable as a string.
And I want to create a list of this type , and of course after I want to add items from this type to the list.

I have found this code on C# , but it seems not work on vb.net :

// Create a List<> of unknown type at compile time.
Type customList = typeof(List<>).MakeGenericType(tempType);
IList objectList = (IList)Activator.CreateInstance(customList);

// Copy items from a PropertyInfo list to the object just created
object o = objectThatContainsListToCopyFrom;
PropertyInfo p = o.GetType().GetProperty("PropertyName");
IEnumerable copyFrom = p.GetValue(o, null);
foreach(object item in copyFrom) objectList.Add(item); // Will throw exceptions if the types don't match.

// Iterate and access the items of "objectList"
// (objectList declared above as non-generic IEnumerable)
foreach(object item in objectList) { Debug.WriteLine(item.ToString()); }

I just want to create the list , and after to add items like this :

List1.Items.Add(object).

What can I do ?
Thank you !

That looks like it should work in C#. What problem do you have with the VB-translation?

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

I don't know c# , so I have used a code translator.
this is the code :

Dim customList As Type = GetType(List(Of )).MakeGenericType(tempType)
Dim objectList As IList = CType(Activator.CreateInstance(customList), IList)

' Copy items from a PropertyInfo list to the object just created
Dim o As Object = objectThatContainsListToCopyFrom
Dim p As PropertyInfo = o.[GetType]().GetProperty("PropertyName")
Dim copyFrom As IEnumerable = p.GetValue(o, Nothing)
For Each item As Object In copyFrom
    objectList.Add(item)
Next
' Will throw exceptions if the types don't match.
' Iterate and access the items of "objectList"
' (objectList declared above as non-generic IEnumerable)
For Each item As Object In objectList
    Debug.WriteLine(item.ToString())
Next

It shows several errors , but the first is on second line :

Error  103 Too few type arguments to 'System.Collections.Generic.IList(Of T)'

This works for me:

VB

Option Explicit On
Option Strict On

Imports System.Reflection

Module Module1

    Public Class ChildClass
    End Class

    Public Class SomeClass
        Public Property Children As ICollection(Of ChildClass) = New HashSet(Of ChildClass)
    End Class

    Sub Main()
        Dim tempType = GetType(ChildClass)
        Dim someClass = New SomeClass
        someClass.Children.Add(New ChildClass)

        Dim customList As Type = GetType(List(Of )).MakeGenericType(tempType)
        Dim objectList As IList = CType(Activator.CreateInstance(customList), IList)

        ' Copy items from a PropertyInfo list to the object just created
        Dim o As Object = someClass
        Dim p As PropertyInfo = o.[GetType]().GetProperty("Children")
        Dim copyFrom As IEnumerable = CType(p.GetValue(o, Nothing), IEnumerable)
        For Each item As Object In copyFrom
            objectList.Add(item)
        Next
        ' Will throw exceptions if the types don't match.
        ' Iterate and access the items of "objectList"
        ' (objectList declared above as non-generic IEnumerable)
        For Each item As Object In objectList
            Debug.WriteLine(item.ToString())
        Next
    End Sub

End Module

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

sorry , but the Ilist type is unknown .
Everytime I get an error that :

Error  103 Too few type arguments to 'System.Collections.Generic.IList(Of T)'

I don't know why ?

Do you get this error also when running my code on its own in a new console-project?

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

Yes , Ilist and Ienumerable are unknown and produce a similar error message that I have posted before.

I wouldn't know why it should be neccessary for you, as it works for me without, but try it with these imports:

VB

Imports System.Collections
Imports System.Collections.Generic

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

I add :

Imports System.Collections

and now the errors are resolved.
But I have some problems in runtime

I want first to initialize an empty list.
Because if I have just the :
```
dim itemlist as Ilist
```

( Before calling these 2 lines

VB

Dim customList As Type = GetType(List(Of )).MakeGenericType(GetType(MyClass))
        itemlist = CType(Activator.CreateInstance(customList), IList)

How can I check if the list is empty or ?? something similar. But I want a general checkin mode , because the same expression must be correct even when I clear the list and I want to check if empty ( before initializing for a new type ).

( I try to use

If itemlist.Count > 0 Then

but doesn't work.

I have a hard time understanding that - can you explain it a bit more detailed?

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

ok.
I need a way to detect that this list is empty.
But the expression that should do this , must include 2 cases :

The list is not yet created . ( So it's just declared as mylist as Ilist).
The list is created ( with your code ) but the items are deleted ( or has no items ).

I try with the code :

If mylist.Count..... but this doesn't work.

VB

If mylist IsNot Nothing AndAlso mylist.Count > 0 Then
End If

?

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson