Setting Combobox values

[kejpa]

Hi,

I'm furious! :mad:

After finding out that you don't have the ItemValue property any more which disables you from hardcoding the Item/Itemvalue to a combobox I decided to go with the samples in the help and assign a arraylist to the datasource.

 

When I read my database I get the ItemValue for the combobox. How the f**ing h*ll am I to set the item shown in the combobox?

 

cboType.SelectedValue = oItm.Type

will not work, SelectedValue is nothing!

 

Plz help and exsqueeze my dirty language in this post.

/Kejpa

[pelikan]

repeat after me - OOOOM....

your frustration is baseless. With the Managed Combo control you actually get a

great deal more flexibility than you had in the dark ages of VB6 or C++.

Then, you had an ItemValue field for each list element (a DWORD) - it's still there

in the underlying Windows control, but there are better, type safe ways to accomplish

the kinds of things this field was intended for (back in the days when windows were

written with giant switch statements).

 

It took me a while to get used to incredible binding possibilities of managed controls, so

I sympathize with your confusion (except for the "hard coding" bit - never a good idea)

 

Here's what you have to work with:

DataSource

DisplayMember

ValueMember

SelectedValue

 

Think about what happens when you set the first 3 properties to a table that looks

like this: itemkey, displayValue

Then bind the SelectedValue property to something with:

cbo.DataBindings.Add("SelectedValue", SomeOtherTable, "itemkey")

 

As to the hard coding bit, if all you want is a rigid (itemValue:itemString),

remember that combobox items are objects - not strings. you can define

a Pair object with two fields (itemData, itemString) + overridden ToString method which simply returns the itemString. :eek:

[Mutley]

Hi,

I'm furious! :mad:

After finding out that you don't have the ItemValue property any more which disables you from hardcoding the Item/Itemvalue to a combobox I decided to go with the samples in the help and assign a arraylist to the datasource.

 

When I read my database I get the ItemValue for the combobox. How the f**ing h*ll am I to set the item shown in the combobox?

 

cboType.SelectedValue = oItm.Type

will not work, SelectedValue is nothing!

 

Plz help and exsqueeze my dirty language in this post.

/Kejpa

 

Hello kejpa,

 

You can use the

cboType.Items.Add(oItm.Type)

 

Hope it helped

[kejpa]

You can use the

cboType.Items.Add(oItm.Type)

Hope it helped

No, it's not putting the items into the combobox that's the problem. It's not getting the currently selected either.

It's selecting the item based on a value, which is not the text of the items.

 

When initializing the Combo I do...

Dim oType As New ArrayList()
' ccboItem contains members Item, Value
oType.Add(New ccboItem(30, "0..20mA"))
oType.Add(New ccboItem(31, "4..20mA"))
cboType.DataSource = oADDAType
cboType.DisplayMember = "Value"
cboType.ValueMember = "Item"
cboType.SelectedIndex = -1

Reading my database gives me the value of 31 for type

cboType.SelectedValue = oItm.Type ' oItm.Type=31

And I want to see "4..20mA" in the combobox

 

repeat after me - OOOOM....

your frustration is baseless.

OOOOM?!?! Typo? OOP.... OOP.... OOP...

 

Still pissed. :mad:

/Kejpa

[pelikan]

Just grokked your flok. (by the way, did mean OOOM )

Sounds like you want a simple lookup combo fella.

 

Proof-of-concept

scenario:

Table1 ("Item", "Value")

Table2 ("Blah", Blah1", Blah2", "Item") - "Item" is foreign key to Table1("Item")

 

UI:

ComboBox

.DataSource = ds.Tables("Table1")

.DisplayMember = "Value"

.ValueMember = "Item"

DataGrid

.DataSource = ds

.DataMember = "Table2"

 

finally:

cboTable1.DataBindings.Add("SelectedValue", ds, "Table2.Item")

 

test it:

change the selected row in the datagrid, the combo stays in sync

because SelectedValue is 'simple bound' to Table2.Item

get the CurrencyManager:

myCurrencyManager = CType(me.BindingContext(ds.Tables("Table2")), CurrencyManager)

change the SelectedValue via myCurrencyManager.Position - voila, SelectedIndex

in combo changes.

Edited June 23, 2004 by pelikan

[kejpa]

Just grokked your flok. (by the way, did mean OOOM )

Sounds like you want a simple lookup combo fella.

Sure, simple it should be.

Could you just complete the following code (merely test code)

Sub Form_Load (...Removed)
Dim oType As New ArrayList()
' ccboItem contains members Item, Value
oType.Add(New ccboItem(30, "0..20mA"))
oType.Add(New ccboItem(31, "4..20mA"))
cboType.DataSource = oType
cboType.DisplayMember = "Value"
cboType.ValueMember = "Item"
cboType.SelectedIndex = -1
End Sub

Sub txtType_Leave(...Removed)
   cboType.SelectedValue= val(txtType)  '<-- Here!
End Sub

When I enter 30 in the textbox I want the combo to show me 0..20mA

When I enter 31 in the textbox I want the combo to show me 4..20mA

 

New day, not so mad anymore. Yet.

Regards

/Kejpa

[LionelBrown]

Hope this helps...

 

I'm a VB6 programmer that starting using .net 2003 a couple of days ago, so there may be a better way of doing what you want, but I'll give it a try.

 

If I understand correctly, you have a combobox that displays text but has a key value behind the scenes (used to be able to put in itemdata). You want to select an item in the combobox by specifying the KEY value and not the text that is displayed by the combo. The combo will then display the correct text that is associated with the key value.

 

I think you will have to loop through the combobox and check for a key match, then retrieve the index of the combo and use it to select the correct entry. Here's an example:

 

'I have a class with 2 properties that I use to load my combo:

' PCType is a string, and ID is an integer which stores the key

 

Dim iIndex As Integer

 

With cboPCType

'loop through the objects in the combobox

For iIndex = 0 To .Items.Count - 1

'compare my "key" field of the combobox to the key I want to select

'NOTE: .ID returns my class ID property value, I think you use ITEM

If CType(.Items.Item(iIndex).ID, Long) = (your value here) Then

'I've found the key, so set the combo to the correct entry and exit

.SelectedIndex = iIndex

Exit For

End If

Next

 

If iIndex >= .Items.Count Then

'I've looped through every item in my combobox, and key not found

.SelectedIndex = -1

End If

End With

 

 

Good Luck!

[LionelBrown]

One more thing that might be of use to you. I usually use the same stucture for my objects that I attach to a combobox. The members I use are: strText (a string to contain what I want to display), and lngID (a long integer to hold the key value). So I wrote a sub to handle selecting an item of a combobox based on a key, and use it for all my comboboxes:

 

Private Sub SetCboValue(ByRef cbo As ComboBox, ByVal lID As Long)
       Dim iIndex As Integer
       With cbo
           For iIndex = 0 To .Items.Count - 1
               If CType(.Items.Item(iIndex).lngID, Long) = lID Then
                   .SelectedIndex = iIndex
                   Exit For
               End If
           Next
           If iIndex >= .Items.Count Then .SelectedIndex = -1
       End With
   End Sub

 

I then call the sub anytime I want to select an item. For example:

 

SetCboValue(cboPCtype, myDataRow("PcTypeID"))

or

SetCboValue(cboPCtype, 5)

or

SetCboValue(cboType, val(txtType))

 

I saw you were using an array, but I think this should work with a little tweaking

 

Let me know if you have problems and I'll try it with arrays.

 

Good Luck,

Lionel

[LionelBrown]

Your Code

 

Since I'm spending time trying to get a handle on the differences between vb6 and vb.net anyway, I thought I would give your situation a try as a learning experience. Here's your code (at least what I think you are trying to do):

 

Public Class ccboItem
       Private m_Item As Long
       Private m_Value As String

       Public Sub New(ByVal theDisplay As String, ByVal theID As Long)
           m_Value = theDisplay
           m_Item = theID
       End Sub

       Public Overrides Function ToString() As String
           Return m_Value
       End Function

       Public ReadOnly Property Item() As String
           Get
               Return m_Item
           End Get
       End Property

   End Class

   Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
       Dim oType As New ArrayList
       ' ccboItem contains members Item, Value
       cboType.DisplayMember = "Value"
       cboType.ValueMember = "Item"
       oType.Add(New ccboItem("0..20mA", 30))
       oType.Add(New ccboItem("4..20mA", 31))
       cboType.DataSource = oType
      
       cboType.SelectedIndex = -1
   End Sub


   Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtType.TextChanged

   End Sub

   Private Sub txtType_Leave(ByVal sender As Object, ByVal e As System.EventArgs) Handles txtType.Leave
       'cboType.SelectedValue = Val(txtType) '<-- Here!
       SetCboValue(cboType, Val(txtType.Text))
   End Sub

   Private Sub SetCboValue(ByRef cbo As ComboBox, ByVal lID As Long)
       Dim iIndex As Integer
       With cbo
           For iIndex = 0 To .Items.Count - 1
               If CType(.Items.Item(iIndex).Item, Long) = lID Then
                   .SelectedIndex = iIndex
                   Exit For
               End If
           Next
           If iIndex >= .Items.Count Then .SelectedIndex = -1
       End With
   End Sub

 

 

Hope this is what you need.

 

Lionel

[kejpa]

Thanx Lionel,

that's what I needed, I think it's the line

CType(.Items.Item(iIndex).Item, Long) = lID

that I wasn't finding. Item (after iIndex parenthis) isn't showing up in the intellisense and so I never thought I could use it there.

 

Regards

/Kejpa