How to deal with a ComboBox control

There is a very simple, but very useful control. It may

– be filled dynamically and manually

– accept user input (to disable user input is also possibly)

– pass its data to another control by user’s choice.

Well, let’s list what we are going to do with a combobox today:

1) accept value from a single textbox (by clicking a button)

2) accept values from multiple textboxes (from two of them by clicking a button)

3) accept user input and add it to the list (and discuss how to disable user input)

4) clear the list

5) use a value of user’s choise to set a value of one another control (the caption of the form)

6) Intellisense on user input

7) sorting items

If it’s enough, now turn to coding. Traditionally, the code bundle is attached in the box at right and it’s named, not surprisingly, HowToDealWithAComboBoxControl.zip.

The first our topic is how to accept user input. The following lines of code are taken from the $handler_button1_Click eventhandler:

    $comboBox1.Items.Add($textBox1.Text);
    $comboBox1.Items.AddRange(($textBox1.Text, $textBox2.Text));
    $comboBox1.Items.Add($comboBox1.Text);

In all three cases, data, usually of string type, is added by using such methods as Add(item) or AddRange(array of items). As can be seen, both methods are very easy to use.

Next, how we can prevent typing into a combobox? The answer is to set the DropDownStyle property:

$comboBox1.DropDownStyle =
    [System.Windows.Forms.ComboBoxStyle]::DropDownList;
   

After that, how to clean up our combobox?

$comboBox1.Items.Clear();
   
Next, how to grab a value from inside the user input?

$form1.Text = $comboBox1.Text;

How to sort data?

$comboBox1.Sorted = $true;

At last, how to use Intellisense? Please note, the DropDownStyle property should be set to System.Windows.Forms.ComboBoxStyle]::DropDown.

$comboBox1.AutoCompleteCustomSource.Add("System.Windows.Forms");
$comboBox1.AutoCompleteCustomSource.AddRange(("System.Data", "Microsoft"));
$comboBox1.AutoCompleteMode =
    [System.Windows.Forms.AutoCompleteMode]::SuggestAppend;
$comboBox1.AutoCompleteSource =
    [System.Windows.Forms.AutoCompleteSource]::CustomSource;

To test the Intellisense that is tuned above, type m or s in the combobox.

The whole sample is below:

#Generated Form Function
function GenerateForm {
########################################################################
# Code Generated By: SAPIEN Technologies PrimalForms (Community Edition) v1.0.8.0
# Generated On: 21.07.2010 1:32
# Generated By: Administrator
########################################################################

#region Import the Assemblies
[reflection.assembly]::loadwithpartialname("System.Windows.Forms") | Out-Null
[reflection.assembly]::loadwithpartialname("System.Drawing") | Out-Null
#endregion

#region Generated Form Objects
$form1 = New-Object System.Windows.Forms.Form
$button1 = New-Object System.Windows.Forms.Button
$button2 = New-Object System.Windows.Forms.Button
$textBox2 = New-Object System.Windows.Forms.TextBox
$textBox1 = New-Object System.Windows.Forms.TextBox
$comboBox1 = New-Object System.Windows.Forms.ComboBox
$InitialFormWindowState = New-Object System.Windows.Forms.FormWindowState
#endregion Generated Form Objects

#----------------------------------------------
#Generated Event Script Blocks
#----------------------------------------------
#Provide Custom Code for events specified in PrimalForms.
    #region $handler_comboBox1_SelectedIndexChanged
$handler_comboBox1_SelectedIndexChanged=
{
#TODO: Place custom script here
    try{
    if ($comboBox1.Text.Length -gt 0)
    {
        $form1.Text = $comboBox1.Text;
    }
    }catch{} #in case no items are available
}
    #endregion $handler_comboBox1_SelectedIndexChanged
    #region $handler_button1_Click
$handler_button1_Click=
{
#TODO: Place custom script here
    try{
    #How to add one item
    #$textBox1.Text
    if ($textBox1.Text.Length -gt 0 -and `
        $textBox2.Text.Length -eq 0)
    {
        $comboBox1.Items.Add($textBox1.Text);
        Write-Host "Added " $textBox1.Text "from `$textBox1";
    }
    #$textBox2.Text
    elseif ($textBox1.Text.Length -eq 0 -and `
        $textBox2.Text.Length -gt 0)
    {
        $comboBox1.Items.Add($textBox2.Text);
        Write-Host "Added " $textBox2.Text "from `$textBox2";
    }
    #$textBox1.Text and $textBox2.Text
    elseif ($textBox1.Text.Length -gt 0 -and `
        $textBox2.Text.Length -gt 0)
    {
        $comboBox1.Items.AddRange(($textBox1.Text, $textBox2.Text));
        Write-Host "Added " $textBox1.Text "from `$textBox1";
        Write-Host "Added " $textBox2.Text "from `$textBox2";
    }
    else
    {
        #Nothing to add
        #$textBox1.Text.Length -eq 0
        #$textBox2.Text.Length -eq 0
    }
    #At last, if the user typed something
    if ($comboBox1.Text.Length -gt 0)
    {
        $comboBox1.Items.Add($comboBox1.Text);
        Write-Host "Added " $comboBox1.Text "from `$comboBox1";
    }
    }catch{} #for example, no data in the both textboxes
}
    #endregion $handler_button1_Click
    #region $handler_button2_Click
$handler_button2_Click=
{
#TODO: Place custom script here
    try{
    #Clean up the combo box
    $comboBox1.Items.Clear();
    $comboBox1.Text = "";
    }catch{}
}
    #endregion $handler_button2_Click
$OnLoadForm_StateCorrection=
{#Correct the initial state of the form to prevent the .Net maximized form issue
    $form1.WindowState = $InitialFormWindowState
}

#----------------------------------------------
#region Generated Form Code
    #region $form1
$form1.Text = "Primal Form"
$form1.Name = "form1"
$form1.DataBindings.DefaultDataSourceUpdateMode = 0
$System_Drawing_Size = New-Object System.Drawing.Size
$System_Drawing_Size.Width = 282
$System_Drawing_Size.Height = 220
$form1.ClientSize = $System_Drawing_Size
    #endregion $form1
    #region $button1
$button1.TabIndex = 3
$button1.Name = "button1"
$System_Drawing_Size = New-Object System.Drawing.Size
$System_Drawing_Size.Width = 70
$System_Drawing_Size.Height = 30
$button1.Size = $System_Drawing_Size
$button1.UseVisualStyleBackColor = $True
$button1.Text = "button1"
$System_Drawing_Point = New-Object System.Drawing.Point
$System_Drawing_Point.X = 195
$System_Drawing_Point.Y = 160
$button1.Location = $System_Drawing_Point
$button1.DataBindings.DefaultDataSourceUpdateMode = 0
$button1.add_Click($handler_button1_Click)
$form1.Controls.Add($button1)
    #endregion $button1
    #region $button2
$button2.TabIndex = 4
$button2.Name = "button2"
$System_Drawing_Size = New-Object System.Drawing.Size
$System_Drawing_Size.Width = 70
$System_Drawing_Size.Height = 30
$button2.Size = $System_Drawing_Size
$button2.UseVisualStyleBackColor = $True
$button2.Text = "button2"
$System_Drawing_Point = New-Object System.Drawing.Point
$System_Drawing_Point.X = 15
$System_Drawing_Point.Y = 160
$button2.Location = $System_Drawing_Point
$button2.DataBindings.DefaultDataSourceUpdateMode = 0
$button2.add_Click($handler_button2_Click)
$form1.Controls.Add($button2)
    #endregion $button2
    #region $textBox1
$System_Drawing_Size = New-Object System.Drawing.Size
$System_Drawing_Size.Width = 250
$System_Drawing_Size.Height = 20
$textBox1.Size = $System_Drawing_Size
$textBox1.DataBindings.DefaultDataSourceUpdateMode = 0
$textBox1.Name = "textBox1"
$System_Drawing_Point = New-Object System.Drawing.Point
$System_Drawing_Point.X = 15
$System_Drawing_Point.Y = 70
$textBox1.Location = $System_Drawing_Point
$textBox1.TabIndex = 1
$form1.Controls.Add($textBox1)
    #endregion $textBox1
    #region $textBox2
$System_Drawing_Size = New-Object System.Drawing.Size
$System_Drawing_Size.Width = 250
$System_Drawing_Size.Height = 20
$textBox2.Size = $System_Drawing_Size
$textBox2.DataBindings.DefaultDataSourceUpdateMode = 0
$textBox2.Name = "textBox2"
$System_Drawing_Point = New-Object System.Drawing.Point
$System_Drawing_Point.X = 15
$System_Drawing_Point.Y = 120
$textBox2.Location = $System_Drawing_Point
$textBox2.TabIndex = 2
$form1.Controls.Add($textBox2)
    #endregion $textBox2
    #region $comboBox1
$comboBox1.FormattingEnabled = $True
$System_Drawing_Size = New-Object System.Drawing.Size
$System_Drawing_Size.Width = 250
$System_Drawing_Size.Height = 21
$comboBox1.Size = $System_Drawing_Size
$comboBox1.DataBindings.DefaultDataSourceUpdateMode = 0
$comboBox1.Name = "comboBox1"
$System_Drawing_Point = New-Object System.Drawing.Point
$System_Drawing_Point.X = 15
$System_Drawing_Point.Y = 20
$comboBox1.Location = $System_Drawing_Point
$comboBox1.TabIndex = 0
$comboBox1.add_SelectedIndexChanged($handler_comboBox1_SelectedIndexChanged)

$comboBox1.DropDownStyle =
    [System.Windows.Forms.ComboBoxStyle]::DropDown;
$comboBox1.Sorted = $true;

$comboBox1.AutoCompleteCustomSource.Add("System.Windows.Forms");
$comboBox1.AutoCompleteCustomSource.AddRange(("System.Data", "Microsoft"));
$comboBox1.AutoCompleteMode =
    [System.Windows.Forms.AutoCompleteMode]::SuggestAppend;
$comboBox1.AutoCompleteSource =
    [System.Windows.Forms.AutoCompleteSource]::CustomSource;

$form1.Controls.Add($comboBox1)
    #endregion $comboBox1
#endregion Generated Form Code

#Save the initial state of the form
$InitialFormWindowState = $form1.WindowState
#Init the OnLoad event to correct the initial state of the form
$form1.add_Load($OnLoadForm_StateCorrection)
#Show the Form
$form1.ShowDialog()| Out-Null

} #End Function

#Call the Function
GenerateForm