以编程方式更改索引时，不会触发ComboBox.SelectedIndexChanged

Question

I am working with Windows Forms in C#.net. I have 2 ComboBox and 3 TextBox on a form. When I change the value in ComboBox1 (by interating with the item in the UI) it changes the items and selected item in ComboBox2 .

When the selected index of ComboBox2 is changed, it should change the text in all of the TextBox , but it seems that the SelectedIndexChanged is not being fired.

public void comboSelectionChanged(object sender, EventArgs e)
    {
        //when the selection changes...
        // 1) cast the sender as a comboBox
        ComboBox cBox = (ComboBox)sender;

        // 2) identify the sender
        if (cBox.Name.ToString() == "ComboBox1")
        {   //this is the 1st combo box                

            //load the children of the new selection into the form
            //child of ComboBox1 is ComboBox2
            ComboBox2.Items.Clear();
            ComboBox2.Text = null;
            string selected = null;

            foreach (string item in {"box2_item1","box2_item2"})
            {
                ComboBox2.Items.Add(item);
            }
            //need to set the selection last, because this will (hopefully) fire the selection changed event on the child

            if (selected != null)
            {//here I am actually getting the selected item from XML
                ComboBox2.SelectedItem = selected;
            }
            else
            {//this should be action that is initiated, which should definitely change the selected index
                ComboBox2.SelectedIndex = -1;
            }
        }
        else if (cBox.Name.ToString() == "ComboBox2")
        {   //this is the 2nd combobox              

            //load the children of the new selection into the form
            //the textBoxes are the children
            TextBox1.Text = "some new text that I am getting from XML";
            TextBox2.Text = "some other new text as above.";
            TextBox3.Text = "same thing, one more time" ;
        }
        else
        {   //I messed something up, because the combobox name is invalid
            Debug.Write("Unreachable code encountered: The combobox name {" + cBox.Name.ToString() + "} is not valid!");
            return;
        }

I've tried to simplify this, and hopefully I haven't overdone it with the simplification. As noted, I am getting data from an XML file, and ideally the goal is to use this form to read from and write to the XML file. All of the XML seems to me working fine, so I have left all of that out.

both of the boxes' SelectedIndexChanged events are tied to the code above. What happens is when I change the value of ComboBox1 the values of ComboBox2 are changed, and the selected item is cleared, but the ComboBox2.SeletedIndexChanged event is never fired (breakpoins show me that the code clock is never re-entered), so the none of the TextBox are updated with new data.

I hope that all makes sense and somone can help me figure out what I am doing wrong.

Answer 1

The event handler is just a method so you can just call it. If your handler is named ComboBox2_SelectedIndexChanged you can do:

        ...
        else
        {//this should be action that is initiated, which should definitely change the selected index
            ComboBox2.SelectedIndex = -1;
            ComboBox2_SelectedIndexChanged(ComboBox2, new EventArgs());
        }
        ...

Answer 2

在comboSelectionChanged(object sender, EventArgs e)方法中通过调用自己comboSelectionChanged(object sender, EventArgs e) SelectedIndexChanged事件

ComboBox2_SelectedIndexChanged(ComboBox2, new EventArgs());