Combobox SelectedItem issues

Question

I have to set different values of a variable through the selection of a Combobox. But even if the clause reported in the Combobox is selected, the value is 0. Here is what I wrote:

In the form where the Combobox is located:

Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    ComboBox1.SelectedItem = "Ultra-fast"
End Sub
Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged
    ComboBox1.DropDownStyle = ComboBoxStyle.DropDownList
End Sub

In the form where I have to set the value of the variable (calling the Combobox):

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim growth as Integer
If Form2.ComboBox1.SelectedItem = "Ultra-fast" Then
            growth = 75
ElseIf Form2.ComboBox1.SelectedItem = "Fast" Then
            growth = 150
ElseIf Form2.ComboBox1.SelectedItem = "Medium" Then
            growth = 300
ElseIf Form2.ComboBox1.SelectedItem = "Slow" Then
            growth = 600
End If
End Sub

Where am I doing wrong? I've also checked that the form where the Combobox is opened and it remains active when I call the Combobox. I've setted a label to write the value of "growth" but it always remains equal to zero. Thanks all are gonna answer me. Best regards.

This is not likely to be related to your issue by why would you be setting the `DropDownStyle` in the `SelectedIndexChanged` event handler? Why would you not set it in the designer? — jmcilhinney, Nov 30 '20 at 13:05
Probably you are asking to do the change to the wrong form instance. See https://stackoverflow.com/questions/4698538/why-is-there-a-default-instance-of-every-form-in-vb-net-but-not-in-c — Steve, Nov 30 '20 at 13:06
@jmcilhinney thanks for commenting. I'm not a VB.net expert programmer, so I found something on the internet and I've found that command to block editing from user. I didn't know that this property could be set in the designer. — telemaco10399, Nov 30 '20 at 13:07
@jmcilhinney Could you explain me what "display" means? Form2 is the screen from which I'm importing data to create graphs but when I recall the Combobox2, Form2 remains open — telemaco10399, Nov 30 '20 at 13:09
Please turn on Option Strict. This is a 2 part process. First for the current project - In Solution Explorer double click My Project. Choose Compile on the left. In the Option Strict drop-down select ON. Second for future projects - Go to the Tools Menu -> Options -> Projects and Solutions -> VB Defaults. In the Option Strict drop-down select ON. This will save you from bugs at runtime. You will see that `.SelectedItem` is an `Object`. — Mary, Nov 30 '20 at 18:48

score 0 · Answer 1 · answered Nov 30 '20 at 19:41

On Form2 fill your combo with KeyValue pairs. Then set the display and value members. The data source is the actual items in the combo.

Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    ComboBox1.Items.Add(New KeyValuePair(Of String, Integer)("Ultra-fast", 75))
    ComboBox1.Items.Add(New KeyValuePair(Of String, Integer)("Fast", 150))
    ComboBox1.Items.Add(New KeyValuePair(Of String, Integer)("Medium", 300))
    ComboBox1.Items.Add(New KeyValuePair(Of String, Integer)("Slow", 600))

    ComboBox1.DisplayMember = "Key"
    ComboBox1.ValueMember = "Value"
    ComboBox1.DataSource = ComboBox1.Items
End Sub

In Form1 retrieve the select value. Remember this returns an Object but you can cast it back to its underlying type.

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
    Dim growth = CInt(Form2.ComboBox1.SelectedValue)
    MessageBox.Show(growth.ToString)
End Sub

Combobox SelectedItem issues

1 Answers1