Single thread apartment issue

From my mainform I call the following to open a new form ``` MyForm sth = new MyForm(); sth.show(); ``` Everything works great however this form has a combobox that, when I switch its AutoCompleteMode to suggest and append, I got this exception while showing the form: Current thread must be set to single thread apartment (STA) mode before OLE calls can be made. Ensure that your Main function has STAThreadAttribute marked on it. I have set this attribute on my main function as requested by the exception: ``` [STAThread] static void Main(string[] args) { ... ``` Can I please get some help as to understand what might be wrong. Sample code: ``` private void mainFormButtonCLick (object sender, EventArgs e) { // System.Threading.Thread.CurrentThread.SetApartmentState(ApartmentState.STA); ? MyForm form = new MyForm(); form.show(); } ``` Designer: ``` this.myCombo.AutoCompleteMode = System.Windows.Forms.AutoCompleteMode.Suggest; this.myCombo.AutoCompleteSource = System.Windows.Forms.AutoCompleteSource.ListItems; this.myCombo.FormattingEnabled = true; this.myCombo.Location = new System.Drawing.Point(20, 12); this.myCombo.Margin = new System.Windows.Forms.Padding(4, 5, 4, 5); this.myCombo.Name = "myCombo"; this.myCombo.Size = new System.Drawing.Size(430, 28); this.myCombo.Sorted = true; this.myCombo.TabIndex = 0; phrase"; ``` Setting data source ``` public MyForm(List<string> elem) { InitializeComponent(); populateColorsComboBox(); PopulateComboBox(elem); } public void PopulateComboBox(List<string> list ) { this.myCombo.DataSource = null; this.myCombo.DisplayMember = "text"; this.myCombo.DataSource = list; } ```