驗證規則使用來自另一個控件的值

Question

我正在嘗試做一些我之前認為很容易的事情：在另一個控件的驗證規則中使用一個控件的值。 我的應用程序具有用戶可以輸入的各種參數，這里討論的特定參數定義范圍的起點和終點，用戶通過文本框設置值。

有問題的兩個控件是開始和結束文本框，並且應在驗證中檢查以下條件：

1. 起始值必須大於或等於某個任意值
2. 結束值必須小於或等於某個任意值
3. 起始值必須小於或等於結束值

我已經完成的前兩個條件。 第三個實現起來要困難得多，因為我無法從驗證器訪問結束文本框的值。 即使我可以，有五個不同的范圍（每個都有自己的開始和結束文本框）我正在嘗試驗證，並且必須有一些解決方案比為每個范圍創建驗證規則更優雅。

這是相關的XAML代碼：

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:validators="clr-namespace:CustomValidators"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition/>
        <RowDefinition/>
    </Grid.RowDefinitions>

    <TextBox Name="textboxStart" Grid.Row="0">
        <TextBox.Text>
            <Binding Path="Start" UpdateSourceTrigger="PropertyChanged">
                <Binding.ValidationRules>
                    <validators:MeasurementRangeRule Min="1513" Max="1583"/>
                </Binding.ValidationRules>
            </Binding>
        </TextBox.Text>
    </TextBox>

    <TextBox Name="textboxEnd" Grid.Row="1">
        <TextBox.Text>
            <Binding Path="End" UpdateSourceTrigger="PropertyChanged">
                <Binding.ValidationRules>
                    <validators:MeasurementRangeRule Min="1513" Max="1583"/>
                </Binding.ValidationRules>
            </Binding>
        </TextBox.Text>
    </TextBox>
</Grid>

這是相關的C＃代碼：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Runtime.CompilerServices;
using System.ComponentModel;
using System.Globalization;

namespace WpfApplication1 {
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window {
        public MainWindow () {
            InitializeComponent();
        }

        private decimal _start;
        private decimal _end;
        public event PropertyChangedEventHandler PropertyChanged;

        public decimal Start {
            get { return _start; }
            set {
                _start = value;
                RaisePropertyChanged();
            }
        }

        public decimal End {
            get { return _end; }
            set {
                _end = value;
                RaisePropertyChanged();
            }
        }

        private void RaisePropertyChanged ([CallerMemberName] string propertyName = "") {
            if (PropertyChanged != null) {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}

namespace CustomValidators {

    public class MeasurementRangeRule : ValidationRule {
        private decimal _min;
        private decimal _max;

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

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

        public override ValidationResult Validate (object value, CultureInfo cultureInfo) {
            decimal measurementParameter = 0;

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

            if ((measurementParameter < Min) || (measurementParameter > Max)) {
                return new ValidationResult(false,
                  "Out of range. Enter a parameter in the range: " + Min + " - " + Max + ".");
            } else {
                return new ValidationResult(true, null);
            }
        }
    }
}

這里鏈接的問題似乎是相關的，但我無法理解所提供的答案。

謝謝...

Answer 1

對於任何可能面臨此問題的人來說，實現IDataErrorInfo以更正常地驗證錯誤，並在某些邏輯分組中完成對其他控件的驗證要容易得多。 我將相關屬性（start，end，min和max）封裝在一個類中，將控件綁定到這些屬性，然后使用IDataErrorInfo接口進行驗證。 相關代碼如下......

XAML：

    <TextBox Name="textboxStart" Grid.Row="0" Text="{Binding Path=Start, ValidatesOnDataErrors=True}" Margin="5"/>
    <TextBox Name="textboxEnd" Grid.Row="1" Text="{Binding Path=End, ValidatesOnDataErrors=True}" Margin="5"/>
</Grid>

C＃：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Runtime.CompilerServices;
using System.ComponentModel;

namespace WpfApplication1 {
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window {
        public MainWindow () {
            InitializeComponent();

            Parameter testParameter = new Parameter(0, 10);
            testGrid.DataContext = testParameter;
        }
    }

    public class Parameter: INotifyPropertyChanged, IDataErrorInfo {
        private decimal _start, _end, _min, _max;
        public event PropertyChangedEventHandler PropertyChanged;

        public Parameter () { }

        public Parameter (decimal min, decimal max) {
            this.Min = min;
            this.Max = max;
        }

        public decimal Start {
            get { return _start; }
            set {
                _start = value;
                //RaisePropertyChanged for both Start and End, because one may need to be marked as invalid because of the other's current setting.
                //e.g. Start > End, in which case both properties are now invalid according to the established conditions, but only the most recently changed property will be validated
                RaisePropertyChanged();
                RaisePropertyChanged("End");
            }
        }

        public decimal End {
            get { return _end; }
            set {
                _end = value;
                //RaisePropertyChanged for both Start and End, because one may need to be marked as invalid because of the other's current setting.
                //e.g. Start > End, in which case both properties are now invalid according to the established conditions, but only the most recently changed property will be validated
                RaisePropertyChanged();
                RaisePropertyChanged("Start");
            }
        }

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

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

        private void RaisePropertyChanged ([CallerMemberName] string propertyName = "") {
            if (PropertyChanged != null) {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public string Error {
            get { return string.Empty; }
        }

        public string this[string columnName] {
            get {
                string result = string.Empty;

                switch (columnName) {
                    case "Start":
                        if (Start < Min || Start > Max || Start > End) {
                            result = "Out of range. Enter a value in the range: " + Min + " - " + End + ".";
                        }
                        break;
                    case "End":
                        if (End < Min || End > Max || End < Start) {
                            result = "Out of range. Enter a value in the range: " + Start + " - " + Max + ".";
                        }
                        break;
                };

                return result;
            }
        }
    }
}