How to asynchronously populate combo box on a window form

Is it possible to populate a combo box after the form has loaded. I've tried the following, the code runs; however, the combo box is empty. What am I missing?
thanks!
namespace TRSWin.Inquiry
{
    public delegate TOutput MyAsyncMethod(ref ComboBox myComboBox, object dataSource);
    public partial class PositionInquiry : TRSWin.ParentForm
    {
        public PositionInquiry()
        {
            InitializeComponent();
        }

        public bool BindLookup(ref ComboBox myComboBox, object dataSource)
        {
            myComboBox.DataSource = dataSource;
            myComboBox.DisplayMember = "Description";
            return true;
        }
        public void BeginBindLookup(ref ComboBox myComboBox, object dataSource)
        {
            MyAsyncMethod method = BindLookup;
            method.BeginInvoke(ref myComboBox, dataSource, EndBindLookup, method);
        }
        public void EndBindLookup(IAsyncResult result)
        {
            MyAsyncMethod method = result.AsyncState as MyAsyncMethod;
            //bool b = method.EndInvoke(result); // Can't figure out how to make this call either, so I will ignore for now.
        }
        private void PositionInquiry_Load(object sender, EventArgs e)
        {
            BindLookup(ref cboSymbol, Cache.SymbolLookup);  // Works, populates list
            BeginBindLookup(ref cboSymbol, Cache.SymbolLookup);  // Runs, but list is empty

        }
    }
}

public delegate void InvokeDelegate(); public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { Invoke_Click(sender, e); } private void Invoke_Click(object sender, EventArgs e) { cmb.BeginInvoke(new InvokeDelegate(InvokeMethod)); } public void InvokeMethod() { cmb.Items.AddRange(new object[] { 1,2,3,4,5}); }

1 Reply

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Roei Bar17y ago

Accepted answer

there is no problem with Invoking a Combobox to Async Binding

here is a sample code

the problem is in your delegate

 public delegate TOutput MyAsyncMethod(object dataSource);

try changing it to the delegate as i specified above, since you are putting a ref to the Combo and on threads even though it seems to run, it wont populate the same instance as the Form Combo Instance