Problem with Combobox PreviewKeyDown Enent

ali gholami

Hi.
Follow this Steps:
create new application in c#.net
place 1 combobox and 1 textbox on form
on PreviewKeyDown Event for combobox write a code also for text box
now run the application and set focus to combobox and press any key!
the code you typed run 2 times!! but for textbox run only 1 times!
very thanx
exeuse me for bad english!

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

ali gholami17y ago
Hi, very thanx for this responses,
but i want to handle key down event until my code in previewkeydown event run one time and pressed key no writen to combobox,
for example when i press Ctrl+S on combobox, saveButton click event occure one time and "s" no writen to combobox.
exeuse me for bad english!
Master Billa17y ago
Hi

This is occur before the key down event.So you can write like this way to move your combo box

Here is to

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.previewkeydown.aspx

thank you

Dushan Stankovic17y ago

PreviewKeyDown occurs before the KeyDown event when a key is pressed while focus is on this control.

When you set DropDownStyle property to DropDownList this event occurs only one time, but if you set other two value to DropDownStyle prop event occurs two times.

I think that is event is raised first time for keyboard key pressed and second time for printing pressed key at text field.
I didn't find any different answer on the web.

This example is for debug purpose only:

  private void comboBox1_PreviewKeyDown(object sender, PreviewKeyDownEventArgs e)
        {
            System.Text.StringBuilder messageBoxCS = new System.Text.StringBuilder();
            messageBoxCS.AppendFormat("{0} = {1}", "Alt", e.Alt);
            messageBoxCS.AppendLine();
            messageBoxCS.AppendFormat("{0} = {1}", "Control", e.Control);
            messageBoxCS.AppendLine();
            messageBoxCS.AppendFormat("{0} = {1}", "KeyCode", e.KeyCode);
            messageBoxCS.AppendLine();
            messageBoxCS.AppendFormat("{0} = {1}", "KeyValue", e.KeyValue);
            messageBoxCS.AppendLine();
            messageBoxCS.AppendFormat("{0} = {1}", "KeyData", e.KeyData);
            messageBoxCS.AppendLine();
            messageBoxCS.AppendFormat("{0} = {1}", "Modifiers", e.Modifiers);
            messageBoxCS.AppendLine();
            messageBoxCS.AppendFormat("{0} = {1}", "Shift", e.Shift);
            messageBoxCS.AppendLine();
            messageBoxCS.AppendFormat("{0} = {1}", "IsInputKey", e.IsInputKey);
            messageBoxCS.AppendLine();
            MessageBox.Show(messageBoxCS.ToString(), "PreviewKeyDown Event");

        }