有什么办法不叫控制事件？

Question

Let's say there is event ComboBox_SelectedIndexChange something like this

private void MyComboBox_SelectedIndexChanged(object sender, EventArgs e)
{
  //do something//
}

And i have a function which changes value of ComboBox.

Private void MyFunction()
{
   MyComboBox.Text = "New Value";
}

Can i make MyFunction prevent from calling the event MyComboBox_SelectedIndexChanged while changing the value of MyComboBox?

Answer 1

Can i make MyFunction prevent from calling the event MyComboBox_SelectedIndexChanged while changing the value of MyComboBox?

No, you cannot. You have two fundamental options, both of which accomplish the same thing:

1. You can unhook the event handler method from the control, set the value, and then reattach the event handler method to the control. For example:

    private void MyFunction() { MyComboBox.SelectedIndexChanged -= MyComboBox_SelectedIndexChanged; MyComboBox.Text = "New Value"; MyComboBox.SelectedIndexChanged += MyComboBox_SelectedIndexChanged; } 

2. You can declare a class-level field that will keep track of whether the value was updated programmatically or by the user. Set the field when you want to update the combo box programmatically, and verify its value in the SelectedIndexChanged event handler method.
   For example:

    private bool allowComboBoxChange = true; private void MyComboBox_SelectedIndexChanged(object sender, EventArgs e) { if (allowComboBoxChange) { //do something } } private void MyFunction() { allowComboBoxChange = false; MyComboBox.Text = "New Value"; allowComboBoxChange = true; } 

Answer 2

You may attach or detach an event handler.

//attach the handler
MyComboBox.SelectedIndexChanged+=(sender,eventArgs)=>
{
  //code
};
//detach the handler
MyComboBox.SelectedIndexChanged-=(sender,eventArgs)=>
{
  //code
};

Or

Private void MyFunction()
{
   comboBox1.SelectedIndexChanged -= new EventHandler(TestIt);
   MyComboBox.Text = "New Value";
   comboBox1.SelectedIndexChanged += new EventHandler(TestIt);
}

private void TestIt(object sender, EventArgs e)
{
  //do something//
}