TextBox1.TextChanged事件顯示MsgBox兩次

Question

我有TextBox1.TextChanged事件的問題。 我的代碼：

Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged 
    MsgBox("txt was changed") 
    TextBox1.Clear() 
End Sub 

的問題是，MSGBOX顯示兩次，但是我想表明它只是一個時間和清除文本框。我怎樣才能做到這一點？

Answer 1

兩種方式：

暫時移除處理程序，以防止事件再次射擊：

Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged 
    MsgBox("txt was changed") 
    RemoveHandler TextBox1.TextChanged, AddressOf TextBox1_TextChanged 
    TextBox1.Clear() 
    AddHandler TextBox1.TextChanged, AddressOf TextBox1_TextChanged 
End Sub 

或

創建一個字段，檢查如果事件是從自身起源：

Dim textBoxAlreadyChanging As boolean = False 

Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged 
    If Not textBoxAlreadyChanging Then 
     MsgBox("txt was changed") 
     textBoxAlreadyChanging = True 
     TextBox1.Clear() 
     textBoxAlreadyChanging = False 
    End If 
End Sub