WinRT TextBox MaxLength不會將\ n \ r計爲兩個字符

Question

我有TextBox並將MaxLength設置爲10，但按下Enter鍵時它將接受11個字符。看起來它計數爲\ n \ r爲1個字符而不是2個。無論如何可以將它計數爲\ n \ r作爲兩個字符長度嗎？

Answer 1

如果你真的想允許換行符在文本框，並限制其文本的長度，我看到兩個選項：

• 通過轉換綁定MaxLength，使其按照多少行改變其值如this question

• 所示，或者，您可以定義自己的附屬屬性MaxLength，以正確計算文本長度。這可能看起來有點像下面的（只是作爲一個例子，你需要去適應，要考慮到特殊情況等）：

  public class TextBoxExtensions: DependencyObject 
  { 
      public static readonly DependencyProperty MaxLengthProperty = DependencyProperty.RegisterAttached(
       "MaxLength", typeof (int), typeof (MaxLengthBehavior), new PropertyMetadata(default(int), PropertyChangedCallback)); 
  
      public static void SetMaxLength(DependencyObject element, int value) 
      { 
       element.SetValue(MaxLengthProperty, value); 
      } 
  
      public static int GetMaxLength(DependencyObject element) 
      { 
       return (int) element.GetValue(MaxLengthProperty); 
      } 
  
      private static void PropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs args) 
      { 
       var tb = dependencyObject as TextBox; 
       if (tb != null) 
       { 
        tb.KeyDown -= TbOnKeyDown; 
        tb.KeyDown += TbOnKeyDown; 
       } 
      } 
  
      private static void TbOnKeyDown(object sender, KeyRoutedEventArgs args) 
      { 
       var tb = sender as TextBox; 
       if (tb != null) 
       { 
        int max = GetMaxLength(tb); 
        if (tb.Text.Length >= max) 
         args.Handled = true; 
       } 
      } 
  } 
  

<TextBox local:TextBoxExtensions.MaxLength="10" />