Binding Label and Value to ComboBox Winforms

Question

I have this code

Public Sub FillCategoryCombobox(ByVal categoryList As List(Of tblCategory), ByVal LvName As ComboBox)
    LvName.Items.Clear()
    Dim itemValue = New Dictionary(Of Integer, String)()
    For Each category As tblCategory In categoryList
        itemValue.Add(category.CategoryID, category.CategoryName)
    Next category
    LvName.DataSource = New BindingSource(itemValue, Nothing)
    LvName.DisplayMember = "Value"
    LvName.ValueMember = "Key"
End Sub

I receive an error on

LvName.DataSource = New BindingSource(itemValue, Nothing)

Value cannot be null

Answer 1

Never ever tried to bind a dictionary to a control's datasource or bindingsource. Maybe that's not possible. Why don't you use your categoryList as a DataSource (for the BindingSource or directly)

combo1.DataSource = categoryList
combo1.DisplayMember = "CategoryName"
combo1.ValueMember = "CategoryID"

or if you need to maintain the position:

dim bs as new BindingSource(categoryList, nothing)
combo1.DataSource = bs
combo1.DisplayMember = "CategoryName"
combo1.ValueMember = "CategoryID"    

or create a List(of category) instead of a Dictionary.

btw. a full stack trace is always helpfull.

Answer 2

You can bind a dictionary to a datasource by using the ToList() method of the dictionary.

Edit

Some code:

LvName.DataSource = itemValue.ToList()
LvName.DisplayMember = "Value"
LvName.ValueMember = "Key"