Re: ComboBox unique ValueMember and non-unique DisplayMember

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Okay I don't think I'm understanding your architecture. I was under the
impression that you are trying to use the combobox to display a lookup list
of values and store the value's ID into the data table you're editing. Is
that correct? If so then you will not be able to allow the user to type into
the combobox because there will be no associated ID with the text they type.
Now if you want to store the lookup table's Name field instead, then you can
allow them to type in the text, but you would need to bind to a string field
instead of an integer in the table you're editing. However, since you have
two duplicate Name values in the lookup table, the combobox would always
display the first one in the list that matched. Does that make sense? So for
instance you could do:

Me.ComboBox1.DataSource = MyLookupTable
Me.ComboBox1.ValueMember = "Name"
Me.ComboBox1.DisplayMember = "Name"

Me.ComboBox1.DataBindings.Add("SelectedValue", MyDataset,
"MyTable.LookupName")
Me.ComboBox1.DataBindings.Add("Text", MyDataset, "MyTable.LookupName")

Then I would move the call to EndCurrentEdit into the combobox's validating
event handler so you could pick up any direct edits the user made.

-B

"cryolitte" <a@xxxxx> wrote in message
news:u70HWTHQFHA.2132@xxxxxxxxxxxxxxxxxxxxxxx
> Hi Beth,
>
> Thanks again for your help.
>
> After a few moments of head-scratching, I think I've narrowed it down to
> this line:
> Me.ComboBox1.DropDownStyle =
> System.Windows.Forms.ComboBoxStyle.DropDownList
> As it is, it works fine. Except for the fact that user cannot type
> anything
> into the textbox portion of the ComboBox.
>
> If I change it to:
> Me.ComboBox1.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDown
> The ComboBox then starts exhibiting the behavior that I have described.
>
> Unfortunately I need to use the DropDown style to let users type into the
> textbox portion.
>
> TIA,
> Cryo
>
> "Beth Massi [Architect MVP]" <bmassi@xxxxxxxxxxx> wrote in message
> news:Oz4RFsEQFHA.3196@xxxxxxxxxxxxxxxxxxxxxxx
>> Okay I think it will be easier to figure out if I just write you an
> example
>> ;-). This example uses the SQL Northwind database. It selects Regions and
>> Territories, sets up a relation and has combobox that binds the selected
>> value to the Territories.RegionID field. I'm putting a duplicate row into
>> the Region table to simulate your scenario and it works fine. Note the
> call
>> to EndCurrentEdit in the SelectedIndexChanged event handler.
>>
>> Public Class Form3
>> Inherits System.Windows.Forms.Form
>>
>> #Region " Windows Form Designer generated code "
>>
>> Public Sub New()
>> MyBase.New()
>>
>> 'This call is required by the Windows Form Designer.
>> InitializeComponent()
>>
>> 'Add any initialization after the InitializeComponent() call
>>
>> End Sub
>>
>> 'Form overrides dispose to clean up the component list.
>> Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
>> If disposing Then
>> If Not (components Is Nothing) Then
>> components.Dispose()
>> End If
>> End If
>> MyBase.Dispose(disposing)
>> End Sub
>>
>> 'Required by the Windows Form Designer
>> Private components As System.ComponentModel.IContainer
>>
>> 'NOTE: The following procedure is required by the Windows Form Designer
>> 'It can be modified using the Windows Form Designer.
>> 'Do not modify it using the code editor.
>> Friend WithEvents TextBox2 As System.Windows.Forms.TextBox
>> Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
>> Friend WithEvents Label1 As System.Windows.Forms.Label
>> Friend WithEvents Label2 As System.Windows.Forms.Label
>> Friend WithEvents Label4 As System.Windows.Forms.Label
>> Friend WithEvents ComboBox1 As System.Windows.Forms.ComboBox
>> Friend WithEvents Label3 As System.Windows.Forms.Label
>> Friend WithEvents TextBox3 As System.Windows.Forms.TextBox
>> Friend WithEvents Button1 As System.Windows.Forms.Button
>> <System.Diagnostics.DebuggerStepThrough()> Private Sub
>> InitializeComponent()
>> Me.TextBox2 = New System.Windows.Forms.TextBox
>> Me.TextBox1 = New System.Windows.Forms.TextBox
>> Me.Label1 = New System.Windows.Forms.Label
>> Me.Label2 = New System.Windows.Forms.Label
>> Me.Label4 = New System.Windows.Forms.Label
>> Me.TextBox3 = New System.Windows.Forms.TextBox
>> Me.ComboBox1 = New System.Windows.Forms.ComboBox
>> Me.Label3 = New System.Windows.Forms.Label
>> Me.Button1 = New System.Windows.Forms.Button
>> Me.SuspendLayout()
>> '
>> 'TextBox2
>> '
>> Me.TextBox2.Location = New System.Drawing.Point(192, 56)
>> Me.TextBox2.Name = "TextBox2"
>> Me.TextBox2.Size = New System.Drawing.Size(160, 20)
>> Me.TextBox2.TabIndex = 5
>> Me.TextBox2.Text = "TextBox2"
>> '
>> 'TextBox1
>> '
>> Me.TextBox1.Location = New System.Drawing.Point(192, 24)
>> Me.TextBox1.Name = "TextBox1"
>> Me.TextBox1.Size = New System.Drawing.Size(48, 20)
>> Me.TextBox1.TabIndex = 4
>> Me.TextBox1.Text = "TextBox1"
>> '
>> 'Label1
>> '
>> Me.Label1.AutoSize = True
>> Me.Label1.Location = New System.Drawing.Point(24, 24)
>> Me.Label1.Name = "Label1"
>> Me.Label1.Size = New System.Drawing.Size(112, 16)
>> Me.Label1.TabIndex = 6
>> Me.Label1.Text = "Territories.TerritoryID"
>> '
>> 'Label2
>> '
>> Me.Label2.AutoSize = True
>> Me.Label2.Location = New System.Drawing.Point(24, 56)
>> Me.Label2.Name = "Label2"
>> Me.Label2.Size = New System.Drawing.Size(157, 16)
>> Me.Label2.TabIndex = 7
>> Me.Label2.Text = "Territories.TerritoryDescription"
>> '
>> 'Label4
>> '
>> Me.Label4.AutoSize = True
>> Me.Label4.Location = New System.Drawing.Point(24, 120)
>> Me.Label4.Name = "Label4"
>> Me.Label4.Size = New System.Drawing.Size(109, 16)
>> Me.Label4.TabIndex = 10
>> Me.Label4.Text = "Territorries.RegionID"
>> '
>> 'TextBox3
>> '
>> Me.TextBox3.Location = New System.Drawing.Point(192, 120)
>> Me.TextBox3.Name = "TextBox3"
>> Me.TextBox3.Size = New System.Drawing.Size(48, 20)
>> Me.TextBox3.TabIndex = 8
>> Me.TextBox3.Text = "TextBox4"
>> '
>> 'ComboBox1
>> '
>> Me.ComboBox1.DropDownStyle =
>> System.Windows.Forms.ComboBoxStyle.DropDownList
>> Me.ComboBox1.Location = New System.Drawing.Point(192, 88)
>> Me.ComboBox1.Name = "ComboBox1"
>> Me.ComboBox1.Size = New System.Drawing.Size(160, 21)
>> Me.ComboBox1.TabIndex = 11
>> '
>> 'Label3
>> '
>> Me.Label3.AutoSize = True
>> Me.Label3.Location = New System.Drawing.Point(24, 88)
>> Me.Label3.Name = "Label3"
>> Me.Label3.Size = New System.Drawing.Size(40, 16)
>> Me.Label3.TabIndex = 12
>> Me.Label3.Text = "Region"
>> '
>> 'Button1
>> '
>> Me.Button1.Location = New System.Drawing.Point(296, 144)
>> Me.Button1.Name = "Button1"
>> Me.Button1.Size = New System.Drawing.Size(96, 23)
>> Me.Button1.TabIndex = 13
>> Me.Button1.Text = "Show Changes"
>> '
>> 'Form3
>> '
>> Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
>> Me.ClientSize = New System.Drawing.Size(432, 182)
>> Me.Controls.Add(Me.Button1)
>> Me.Controls.Add(Me.Label3)
>> Me.Controls.Add(Me.ComboBox1)
>> Me.Controls.Add(Me.Label4)
>> Me.Controls.Add(Me.TextBox3)
>> Me.Controls.Add(Me.Label2)
>> Me.Controls.Add(Me.Label1)
>> Me.Controls.Add(Me.TextBox2)
>> Me.Controls.Add(Me.TextBox1)
>> Me.Name = "Form3"
>> Me.Text = "Form3"
>> Me.ResumeLayout(False)
>>
>> End Sub
>>
>> #End Region
>>
>> Private MyDataset As DataSet
>>
>> Private Class DataAccess
>> Private Const SQL_CONNECTION_STRING As String = _
>> "Data Source=localhost;" & _
>> "Initial Catalog=Northwind;" & _
>> "Integrated Security=SSPI"
>>
>> Public Shared Sub LoadData(ByRef ds As DataSet)
>> ds = New DataSet
>> Dim da, da2 As SqlDataAdapter
>> Dim cnn As SqlConnection
>> Try
>> cnn = New SqlConnection(SQL_CONNECTION_STRING)
>>
>> da = New SqlDataAdapter("SELECT * FROM Region", cnn)
>> da.Fill(ds, "Region")
>>
>> With ds.Tables("Region")
>> If .Rows.Count > 0 Then
>> '-- Load a "Duplicate" row. has a unique primary key,
>> '-- but same description as first row.
>> Dim values As Object() = {.Rows.Count + 1,
>> .Rows(0)("RegionDescription")}
>> .LoadDataRow(values, True)
>> End If
>> End With
>>
>> da = New SqlDataAdapter("SELECT * FROM Territories", cnn)
>> da.Fill(ds, "Territories")
>>
>> ds.Relations.Add("Region_Territories", _
>> ds.Tables("Region").Columns("RegionID"), _
>> ds.Tables("Territories").Columns("RegionID"))
>>
>> ds.DataSetName = "RegionTerritories"
>>
>> Catch Exp As Exception
>> MessageBox.Show(Exp.Message)
>> End Try
>> End Sub
>>
>> End Class
>>
>> Private Sub Form3_Load(ByVal sender As System.Object, ByVal e As
>> System.EventArgs) Handles MyBase.Load
>> DataAccess.LoadData(MyDataset)
>>
>> Me.ComboBox1.DataSource = MyDataset.Tables("Region")
>> Me.ComboBox1.ValueMember = "RegionID"
>> Me.ComboBox1.DisplayMember = "RegionDescription"
>>
>> Me.ComboBox1.DataBindings.Add("SelectedValue", MyDataset,
>> "Territories.RegionID")
>>
>> Me.TextBox1.DataBindings.Add("Text", MyDataset,
> "Territories.TerritoryID")
>> Me.TextBox2.DataBindings.Add("Text", MyDataset,
>> "Territories.TerritoryDescription")
>> Me.TextBox3.DataBindings.Add("Text", MyDataset, "Territories.RegionID")
>> End Sub
>>
>> Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As
>> System.Object,
>> ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
>> '-- This forces the comboxbox's value to be written to the dataset.
>> Dim cm As CurrencyManager = Me.BindingContext(MyDataset, "Territories")
>> cm.EndCurrentEdit()
>> End Sub
>>
>> Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
>> System.EventArgs) Handles Button1.Click
>> '-- View the diffgram in the web browser
>> Try
>> If Not (MyDataset Is Nothing) Then
>>
>> Dim cFileName As String =
>> Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData)
> +
>> "\Diff"
>> Dim dsDiffgram As DataSet
>>
>> If MyDataset.HasChanges Then
>> dsDiffgram = MyDataset.GetChanges()
>> dsDiffgram.WriteXml(cFileName + MyDataset.DataSetName + ".xml",
>> XmlWriteMode.DiffGram)
>> System.Diagnostics.Process.Start("file://" + cFileName +
>> MyDataset.DataSetName + ".xml")
>> Else
>> MessageBox.Show("Please make changes first.", "Show Changes",
>> MessageBoxButtons.OK, MessageBoxIcon.Information)
>> End If
>> End If
>> Catch exp As Exception
>> End Try
>> End Sub
>>
>> End Class
>>
>>
>>
>>
>> "cryolitte" <a@xxxxx> wrote in message
>> news:%23oJbCjBQFHA.3628@xxxxxxxxxxxxxxxxxxxxxxx
>> > 1). Setting it up kinda like this:
>> > DataTable dt = generateTestDataTable(); // in here column ID is set
> as
>> > Unique
>> > comboBox1.DataSource = dt;
>> > comboBox1.ValueMember = "ID";
>> > comboBox1.DisplayMember = "Name";
>> >
>> > 2). Then I added the data bindings, as suggested:
>> > comboBox1.DataBindings.Add("SelectedValue", dt, "ID");
>> >
>> > 3). But then I start getting a ConstraintException whenever I make a
>> > selection in the dropdown. Additional information: Column 'ID' is
>> > constrained to be unique. Value '4' (or whatever was selected) is
> already
>> > present.
>> >
>> > Why is this being thrown? I am not trying to edit or insert into the
>> > DataTable. I only wish to select a row in it (and get the Combo to
>> > remember
>> > it!). When I click on the dropdown button, it is still automatically
>> > re-selected to the first matching (based on DisplayValue) row.
>> >
>> > 4). Just to see what happens, went back, set dt.Columns["ID"].Unique =
>> > false. Then, whenever I select something, it updates its ID with the
>> > current
>> > SelectedValue...
>> >
>> > 5). Set Unique = true again. I then tried calling
>> > CurrencyManager.EndCurrentEdit() again in both DropDown and DrawItem
>> > events,
>> > and my selectedItem/Index/Value is still being overwritten.
>> > ConstraintException was also thrown (because of the new data-binding, I
>> > think).
>> >
>> > Seriously, I can't be the first one asking this question...lol...
>> >
>> >
>> > "Beth Massi [Architect MVP]" <bmassi@xxxxxxxxxxx> wrote in message
>> > news:eCqa5q%23PFHA.3596@xxxxxxxxxxxxxxxxxxxxxxx
>> >> How are you setting up the databindings to your dataset? Are you doing
>> >> something like this?:
>> >>
>> >> Me.ComboBox1.DataSource = MyLookupTable
>> >> Me.ComboBox1.ValueMember = "ID"
>> >> Me.ComboBox1.DisplayMember = "Name"
>> >> Me.ComboBox1.DataBindings.Add("SelectedValue", myDataSet,
> "Table1.MyID")
>> >>
>> >> "cryolitte" <a@xxxxx> wrote in message
>> >> news:OnCW828PFHA.2560@xxxxxxxxxxxxxxxxxxxxxxx
>> >> > Also, as you suggested, I tried calling
>> >> > CurrencyManager.EndCurrentEdit()
>> >> > in
>> >> > the DropDown and DrawItem events. The ComboBox still selected the
> first
>> >> > matching item based on DisplayValue.
>> >> >
>> >> >
>> >> >
>> >> > "Beth Massi [Architect MVP]" <bmassi@xxxxxxxxxxx> wrote in message
>> >> > news:OPAe8c8PFHA.1528@xxxxxxxxxxxxxxxxxxxxxxx
>> >> >> Does the problem still happen if the Names are different? If so,
>> >> >> you
>> >> >> probably just need to call EndCurrentEdit on the CurrencyManager.
>> >> >>
>> >> >> -B
>> >> >
>> >> >
>> >>
>> >>
>> >
>> >
>>
>>
>
>


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