How do I Change comboBox.Text inside a comboBox.SelectedIndexChanged event?

Code example:

private void comboBox_SelectedIndexChanged(object sender, EventArgs e)
{
	if(some condition)
	{
		comboBox.Text = "new string"
	}
}

My problem is that the comboBox text always shows the selected index's string value and not the new string. Is the a way round this?

In short, .NET is trying to prevent an endless loop that could occur. When a change to the Text property occurs, .NET will try to match that new value to the current items and change the index for you, thereby firing the SelectedIndexChanged event again.

People coming here looking for a VB implementation of Delegates can refer to the code below

'Declares a delegate sub that takes no parameters
Delegate Sub ComboDelegate()

'Loads form and controls
Private Sub LoadForm(sender As System.Object, e As System.EventArgs) _
	Handles MyBase.Load
	ComboBox1.Items.Add("This is okay")
	ComboBox1.Items.Add("This is NOT okay")
	ResetComboBox()
End Sub

'Handles Selected Index Changed Event for combo Box
Private Sub ComboBoxSelectionChanged(sender As System.Object, e As System.EventArgs) _
	Handles ComboBox1.SelectedIndexChanged
	'if option 2 selected, reset control back to original
	If ComboBox1.SelectedIndex = 1 Then
		BeginInvoke(New ComboDelegate(AddressOf ResetComboBox))
	End If

End Sub

'Exits out of ComboBox selection and displays prompt text 
Private Sub ResetComboBox()
	With ComboBox1
		.SelectedIndex = -1
		.Text = "Select an option"
		.Focus()
	End With
End Sub

Further Reading: See this post (mine) on changing Combobox Text in the SelectedIndexChanged Event which goes into a little more detail as to why you need to use a delegate as a workaround to change the ComboBox Text.