WPF Binding Validation 數據驗證

表單的數據驗證往往枯燥無味,又不可避免.
在一個如下表單只有兩個輸入框,和確定按鈕的情況下,正常我們需要做哪些工作呢?

 

1. 如果年齡輸入框輸入了非數字的字符串,輸入框失去焦點后,后面錯誤消息應當能立即提示出來

2.錯誤的提示的內容如果變化,你可能需要修改整個UI設計.(如顯示在輸入框下方)

3.點擊OK按鈕,需要遍歷Window所有輸入框,如果有輸入數據驗證不符合,需要提示錯誤,並將對應的控件獲取焦點.

這很容易么?當這個輸入框再多一些呢?

下面的Demo,看在WPF如何輕松處理這些:

Window里,textBox1,textBox2,textBox3 綁定的數據為:

    public class MyDataSource
    {
        private int _age;
        private int _age2;
        private int _age3;

        public MyDataSource()
        {
            Age = 0;
            Age2 = 0;
        }

        public int Age
        {
            get { return _age; }
            set { _age = value; }
        }
        public int Age2
        {
            get { return _age2; }
            set { _age2 = value; }
        }

        public int Age3
        {
            get { return _age3; }
            set { _age3 = value; }
        }
    }

• 使用自定義驗證規則

<TextBox Name="textBox1" Width="50" FontSize="15"
         Validation.ErrorTemplate="{StaticResource validationTemplate}"
         Style="{StaticResource textBoxInError}"
         Grid.Row="1" Grid.Column="1" Margin="2">
  <TextBox.Text>
    <Binding Path="Age" Source="{StaticResource ods}"
             UpdateSourceTrigger="PropertyChanged" >
      <Binding.ValidationRules>
        <c:AgeRangeRule Min="21" Max="130"/>
      </Binding.ValidationRules>
    </Binding>
  </TextBox.Text>
</TextBox>

 

textBox1 綁定了Age ,並且使用的驗證的規則為 AgeRangeRule ,規則中指定了最小值和最大值,當PropertyChanged時驗證規則將觸發,也就是該控件失去焦點之時. 提示的信息樣式定義在ErrorTemplate里,讓我們再來看一看ErrroTemplate的內容:

      <ControlTemplate x:Key="validationTemplate">
        <DockPanel>
          <TextBlock Foreground="Red" FontSize="20">!</TextBlock>
          <AdornedElementPlaceholder/>
        </DockPanel>
      </ControlTemplate>

AdornedElementPlaceholder 才是這里的點睛之處,此處放置了待驗證的控件,而整個ErrorTemplate正是使用神奇的Adoner實現了錯誤的提示的位置和原排版布局的無關性. 驗證規則和整個代碼完全解耦:

 public class AgeRangeRule : ValidationRule
    {
        private int _min;
        private int _max;

        public AgeRangeRule()
        {
        }

        public int Min
        {
            get { return _min; }
            set { _min = value; }
        }

        public int Max
        {
            get { return _max; }
            set { _max = value; }
        }

        public override ValidationResult Validate(object value, CultureInfo cultureInfo)
        {
            int age = 0;

            try
            {
                if (((string)value).Length > 0)
                    age = Int32.Parse((String)value);
            }
            catch (Exception e)
            {
                return new ValidationResult(false, "Illegal characters or " + e.Message);
            }

            if ((age < Min) || (age > Max))
            {
                return new ValidationResult(false,
                  "Please enter an age in the range: " + Min + " - " + Max + ".");
            }
            else
            {
                return new ValidationResult(true, null);
            }
        }
    }

驗證規則驗證失敗時候拋出的異常顯示在Tip里.

     <Style x:Key="textBoxInError" TargetType="{x:Type TextBox}">
        <Style.Triggers>
          <Trigger Property="Validation.HasError" Value="true">
            <Setter Property="ToolTip"
              Value="{Binding RelativeSource={x:Static RelativeSource.Self},
                              Path=(Validation.Errors)[0].ErrorContent}"/>
          </Trigger>
        </Style.Triggers>
      </Style>

• 使用ExceptionValidationRule

另一種方法,不自定義Rule,如:

 <TextBox Name="textBox3" Width="50" FontSize="15"
             Grid.Row="5" Grid.Column="1" Margin="2"
             Validation.ErrorTemplate="{StaticResource validationTemplate}"
             Style="{StaticResource textBoxInError}">
      <TextBox.Text>
        <Binding Path="Age3" Source="{StaticResource ods}"
                 UpdateSourceTrigger="PropertyChanged">
          <Binding.ValidationRules>
            <ExceptionValidationRule/>
          </Binding.ValidationRules>
        </Binding>
      </TextBox.Text>
    </TextBox>

在后台代碼中:

        BindingExpression myBindingExpression = textBox3.GetBindingExpression(TextBox.TextProperty);
            Binding myBinding = myBindingExpression.ParentBinding;
            myBinding.UpdateSourceExceptionFilter = new UpdateSourceExceptionFilterCallback(ReturnExceptionHandler);
            myBindingExpression.UpdateSource();

 

因為Age3 是Int類型,在textBox3 輸入非int類型,將會引發異常,此時使用Rule的正是系統的ExceptionValidationRule,同樣錯誤信息的模塊不變.

• 驗證所有控件
  
  

        // Validate all dependency objects in a window
          bool IsValid(DependencyObject node)
          {
              // Check if dependency object was passed
              if (node != null)
              {
                  // Check if dependency object is valid.
                  // NOTE: Validation.GetHasError works for controls that have validation rules attached 
                  bool isValid = !Validation.GetHasError(node);
                  if (!isValid)
                  {
                      // If the dependency object is invalid, and it can receive the focus,
                      // set the focus
                      if (node is IInputElement) Keyboard.Focus((IInputElement)node);
                      return false;
                  }
              }
  
              // If this dependency object is valid, check all child dependency objects
              foreach (object subnode in LogicalTreeHelper.GetChildren(node))
              {
                  if (subnode is DependencyObject)
                  {
                      // If a child dependency object is invalid, return false immediately,
                      // otherwise keep checking
                      if (IsValid((DependencyObject)subnode) == false) return false;
                  }
              }
  
              // All dependency objects are valid
              return true;
          }
  

  
  在點擊確定可使用該方法再次驗證,在數據不合法的情況下,使用戶無法提交
  
  

代碼: 下載