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Why do my comboboxes display a value instead of being blank until a value is chosen from dropdown?

Posted on 2006-04-12
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Last Modified: 2010-04-23
I'm rewriting a MSAccess application to VB.NET for more functionality.  I have come a long way with my understanding
but I'm puzzled with what is probably a simple fix for VB.NET novices.

I have a "Clear / New" button on a form for initializing all fields on the form in preparation for data entry of new record.
I have several combo boxes that are required fields and several that are not.  I do not want any of the combo boxes to
display a value until the user click's the dropdown and choses value.  Why do they all contain the first value from the
datatable instead of being blank...AND...more importantly, how do I clear these values until the control is chosen?

Below is my code in various parts:

Public daContacts As New System.Data.OleDb.OleDbDataAdapter
Public dsContacts As New DataSet
Public dtContacts1 As New DataTable
Public dtContacts2 As New DataTable
Public arrMrMrs() As String = {"Mr.", "Mrs.", "Ms.", "Dr."}

daContacts.SelectCommand = New System.Data.OleDb.OleDbCommand("SELECT * FROM Contacts ORDER BY ContactName", TSFConnection)
daContacts.Fill(dsContacts)
dtContacts1 = dsContacts.Tables(0)
dtContacts2 = dsContacts.Tables(0)

cmboBuyer.DataSource = dtContacts1
cmboBuyer.ValueMember = "RecID"
cmboBuyer.DisplayMember = "ContactName"

cmboSeller.DataSource = dtContacts2
cmboSeller.ValueMember = "RecID"
cmboSeller.DisplayMember = "ContactName"

cmboMrMrs.DataSource = arrMrMrs
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Question by:TSFLLC
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5 Comments
 
LVL 4

Expert Comment

by:Vulten
ID: 16440463
Have you tried Combobox1.Text=""

That ought to clear it for you
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LVL 4

Expert Comment

by:Vulten
ID: 16440603
oh... and one more thing... Use

        ComboBox1.Text = ""
        ComboBox1.SelectedIndex = -1 '(Meaning NO item should be selected)

Just to make sure that nothing is selected in the Combobox1... Since It will maintain any selection even if Combobox1.Text =""
0
 

Author Comment

by:TSFLLC
ID: 16440834
I found both of these answers previously and neither one of them worked because they are bound to a datatable.

I did find this piece of code and it does work.
However, I don't like it for (2) reasons:

1) An inordinate amount of code to clear a field.
2) An empty first record when you click on the dropdown.

But it does work....maybe someone else has a better way.

        Dim dr As DataRow
        dr = dsContacts1.Tables(0).NewRow
        dr.Item("ContactIndex") = ""
        dsContacts1.Tables(0).Rows.InsertAt(dr, 0)

        dr = dsContacts2.Tables(0).NewRow
        dr.Item("ContactIndex") = ""
        dsContacts2.Tables(0).Rows.InsertAt(dr, 0)

        cmboSeller.SelectedIndex = 0
        cmboBuyer.SelectedIndex = 0

In MS Access, even though you have a datasource of a SQL statement......
It is simply a matter of cmboseller.text = "" to resolve the problem.

Thanks!
0
 

Author Comment

by:TSFLLC
ID: 16440852
OOPS!   Where I wrote 'ContactIndex'....I meant 'ContactName'
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LVL 14

Accepted Solution

by:
jake072 earned 1500 total points
ID: 16442297
After I set a datasource, when I set the ComboBox's SelectedIndex = -1, and no value is chosen - depending on the type of ComboBox you've chosen...  If the user must select a value (DropDownStyle=DropDownList), than I don't think there's another way.

Jake
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