WPF开发中的第三方库：ValueConverters的使用及属性验证方式

在wpf开发中，你会经常遇到一些需要验证填写内容不能为空，或者是其他的一些规则，比如正则表达式等，以下就是一个示例，同时提供了很多种方式。

1.方式1.使用第三方库：ValueConverters

第一步：在项目中nuget引用ValueConverters

第二步：新建View:ValueConverterView

<Window.Resources>
<conv:BoolToVisibilityConverter x:Key="AgreeConvert" IsInverted="True"/>

</Window.Resources>

<Grid.RowDefinitions>


</Grid.RowDefinitions>

第三步：引用命名空间：xmlns:conv="clr-namespace:ValueConverters;assembly=ValueConverters"，并使用ValueConverterGroup定义每个不一样的验证，并显示，如果按照规则填好，就取消错误提示。

<Window.Resources>
<conv:BoolToVisibilityConverter x:Key="AgreeConvert" IsInverted="True"/>

<conv:ValueConverterGroup x:Key="userNameToVisibilityConverter">
conv:StringIsNotNullOrEmptyConverter/
conv:BoolInverter/
conv:BoolToVisibilityConverter/
</conv:ValueConverterGroup>

<conv:ValueConverterGroup x:Key="passwordToVisibilityConverter">
<conv:IsInRangeConverter MaxValue="16" MinValue="6"/>
conv:BoolInverter/
conv:BoolToVisibilityConverter/
</conv:ValueConverterGroup>

<conv:ValueConverterGroup x:Key="ageToVisibilityConverter">
conv:StringToDecimalConverter/
<conv:IsInRangeConverter MaxValue="99" MinValue="18"/>
conv:BoolInverter/
conv:BoolToVisibilityConverter/
</conv:ValueConverterGroup>

<conv:StringIsNotNullOrEmptyConverter x:Key="StringIsNotNullOrEmptyConverter"/>

</Window.Resources>

<Grid.RowDefinitions>


</Grid.RowDefinitions>

效果如下：

内容填充完，红色提示消失，

当然，这还不算完善，我们可以使用一些更加完善的方式。如以下的形式

2.方式2：使用IDataErrorInfo，直接后台绑定需要提示的内容：

第一步：View页面展示如下：

<Window.Resources>

</Window.Resources>

<Grid.RowDefinitions>


</Grid.RowDefinitions>

新建ValueConverterViewModel，继承:ObservableObject,IDataErrorInfo类

public partial class ValueConverterViewModel:ObservableObject,IDataErrorInfo
{
private string? userName;
public string? UserName
{
get => userName;
set
{
SetProperty(ref userName, value);
OnPropertyChanged(nameof(Error));
}
}

private int age;
public int Age
{
get => age;
set
{
SetProperty(ref age, value);
OnPropertyChanged(nameof(Error));
}
}

public string Error
{
get
{
var errors = new List
{
this[nameof(UserName)],
this[nameof(Age)],
this[nameof(Password)]
};
return string.Join(Environment.NewLine, errors.Where(t => !string.IsNullOrEmpty(t)));
}
}

private string? password;
public string? Password
{
get => password;
set
{
SetProperty(ref password, value);
OnPropertyChanged(nameof(Error));
}
}

public string this[string columnName]
{
get
{
switch (columnName)
{
case nameof(UserName) when string.IsNullOrWhiteSpace(UserName):
return "用户名必须不为空";
case nameof(UserName) when UserName.Length is < 6 or > 10:
return "用户名长度必须在6和10之间";
case nameof(Age) when Age is < 18 or > 110:
return "年龄必须在18和110之间";
case nameof(Password) when string.IsNullOrWhiteSpace(Password):
return "密码必须不为空";
case nameof(Password) when Password.Length is < 8 or > 20:
return "密码长度必须在8和20之间";
default:
return string.Empty;
}
}
}

[RelayCommand]
public void Register()
{
if (Error.Count() > 0)
{
return;
}
MessageBox.Show("注册成功");
}
}

效果如下：

验证通过，点击注册，效果如下：

3.FluentValidation + INotifyDataErrorInfo 实现验证【推荐使用】

3.1 界面View如下：

<Window.Resources>
<conv:BoolToVisibilityConverter x:Key="AgreeConvert" IsInverted="True"/>

<conv:ValueConverterGroup x:Key="userNameToVisibilityConverter">
conv:StringIsNotNullOrEmptyConverter/
conv:BoolInverter/
conv:BoolToVisibilityConverter/
</conv:ValueConverterGroup>

<conv:ValueConverterGroup x:Key="passwordToVisibilityConverter">
<conv:IsInRangeConverter MaxValue="16" MinValue="6"/>
conv:BoolInverter/
conv:BoolToVisibilityConverter/
</conv:ValueConverterGroup>

<conv:ValueConverterGroup x:Key="ageToVisibilityConverter">
conv:StringToDecimalConverter/
<conv:IsInRangeConverter MaxValue="99" MinValue="18"/>
conv:BoolInverter/
conv:BoolToVisibilityConverter/
</conv:ValueConverterGroup>

<conv:StringIsNotNullOrEmptyConverter x:Key="StringIsNotNullOrEmptyConverter"/>

</Window.Resources>

<Grid.RowDefinitions>


</Grid.RowDefinitions>

当前的 View 使用了 INotifyDataErrorInfo 搭配 FluentValidation 进行验证，已经是很现代且推荐的方式，但 WPF 的默认控件不直接显示错误提示文本，还需要设置 验证模板 (ValidationTemplate) 或使用 Adorner 来显示错误提示。绑定需要设置 NotifyOnValidationError=True。

3.2 安装FluentValidation

Install-Package FluentValidation

3.3 新建ViewModel类：ValueConverterViewModel，继承ObservableObject, INotifyDataErrorInfo

public partial class ValueConverterViewModel : ObservableObject, INotifyDataErrorInfo
{
private readonly IValidator _validator;
private readonly Dictionary<string, List> _errors = new();

public ValueConverterViewModel()
{
_validator = new ValueConverterViewModelValidator();
}

[ObservableProperty]
private string? userName;

[ObservableProperty]
private int age;

[ObservableProperty]
private string? password;

partial void OnUserNameChanged(string? value)
{
ValidateProperty(nameof(UserName));
}

partial void OnAgeChanged(int value)
{
ValidateProperty(nameof(Age));
}

partial void OnPasswordChanged(string? value)
{
ValidateProperty(nameof(Password));
}

public bool HasErrors => _errors.Any();

public event EventHandler? ErrorsChanged;

public IEnumerable GetErrors(string? propertyName)
{
if (propertyName != null && _errors.TryGetValue(propertyName, out var errors))
{
return errors;
}
return Enumerable.Empty();
}

private void ValidateProperty(string propertyName)
{
//var context = new ValidationContext(this)
// .CloneForMember(propertyName);

// 创建只验证特定属性的 ValidatorSelector
var selector = new MemberNameValidatorSelector(new[] { propertyName });

// 正确创建 ValidationContext 并传入 selector
var context = new ValidationContext(this, new PropertyChain(), selector);

var result = _validator.Validate(context);

// 移除旧错误
if (_errors.ContainsKey(propertyName))
{
_errors.Remove(propertyName);
OnErrorsChanged(propertyName);
}

// 添加新错误
var propertyErrors = result.Errors
.Where(e => e.PropertyName == propertyName)
.Select(e => e.ErrorMessage)
.ToList();

if (propertyErrors.Any())
{
_errors[propertyName] = propertyErrors;
OnErrorsChanged(propertyName);
}
}

private void OnErrorsChanged(string propertyName)
{
ErrorsChanged?.Invoke(this, new DataErrorsChangedEventArgs(propertyName));
}

[RelayCommand(CanExecute = nameof(CanRegister))]
public void Register()
{
MessageBox.Show("注册成功");
}

public bool CanRegister() => !HasErrors;

}

3.4 新建类ValueConverterViewModelValidator，这是用于属性跪着提示类

public class ValueConverterViewModelValidator : AbstractValidator
{
public ValueConverterViewModelValidator()
{
RuleFor(x => x.UserName)
.NotEmpty().WithMessage("用户名必须不为空")
.Length(6, 10).WithMessage("用户名长度必须在6和10之间");

RuleFor(x => x.Age)
.InclusiveBetween(18, 110).WithMessage("年龄必须在18和110之间");

RuleFor(x => x.Password)
.NotEmpty().WithMessage("密码必须不为空")
.Length(8, 20).WithMessage("密码长度必须在8和20之间");
}
}

3.5 效果如下：

4.DataAnnotationsValidator+INotifyDataErrorInfo 实现验证

4.1 新建View页如下：

<Window.Resources>
<conv:BoolToVisibilityConverter x:Key="AgreeConvert" IsInverted="True"/>

<conv:ValueConverterGroup x:Key="userNameToVisibilityConverter">
conv:StringIsNotNullOrEmptyConverter/
conv:BoolInverter/
conv:BoolToVisibilityConverter/
</conv:ValueConverterGroup>

<conv:ValueConverterGroup x:Key="passwordToVisibilityConverter">
<conv:IsInRangeConverter MaxValue="16" MinValue="6"/>
conv:BoolInverter/
conv:BoolToVisibilityConverter/
</conv:ValueConverterGroup>

<conv:ValueConverterGroup x:Key="ageToVisibilityConverter">
conv:StringToDecimalConverter/
<conv:IsInRangeConverter MaxValue="99" MinValue="18"/>
conv:BoolInverter/
conv:BoolToVisibilityConverter/
</conv:ValueConverterGroup>
<conv:StringIsNotNullOrEmptyConverter x:Key="StringIsNotNullOrEmptyConverter"/>

</Window.Resources>

<Grid.RowDefinitions>


</Grid.RowDefinitions>

4.2 新建ViewModel：ValueConverterViewModel，继承ObservableValidator

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Windows;

namespace WPFDemoMVVM.ViewModel
{
#region INotifyDataErrorInfo + DataAnnotations 实现属性验证
public partial class ValueConverterViewModel : ObservableValidator
{
private readonly Dictionary<string, List> _errors = new();

[ObservableProperty]
[Required(ErrorMessage = "用户名必须不为空")]
[MinLength(6, ErrorMessage = "用户名长度不能少于6位")]
[MaxLength(10, ErrorMessage = "用户名长度不能超过10位")]
private string? userName;

[ObservableProperty]
[Required(ErrorMessage = "密码必须不为空")]
[MinLength(8, ErrorMessage = "密码长度不能少于8位")]
[MaxLength(20, ErrorMessage = "密码长度不能超过20位")]
private string? password;

[ObservableProperty]
[Range(18, 110, ErrorMessage = "年龄必须在18到110之间")]
private int age;

public ValueConverterViewModel()
{
PropertyChanged += (s, e) => ValidateProperty(e.PropertyName!);
}

private void ValidateProperty(string propertyName)
{
if (string.IsNullOrEmpty(propertyName))
return;

var propertyInfo = GetType().GetProperty(propertyName);
if (propertyInfo == null)
return;

var context = new ValidationContext(this)
{
MemberName = propertyName
};

var results = new List<System.ComponentModel.DataAnnotations.ValidationResult>();
var propertyValue = propertyInfo.GetValue(this);
Validator.TryValidateProperty(propertyValue, context, results);

if (_errors.ContainsKey(propertyName))
{
_errors.Remove(propertyName);
OnErrorsChanged(propertyName);
}

if (results.Any())
{
_errors[propertyName] = results.Select(r => r.ErrorMessage!).ToList();
OnErrorsChanged(propertyName);
}
}

public bool HasErrors => _errors.Any();

public event EventHandler? ErrorsChanged;

public IEnumerable GetErrors(string? propertyName)
{
if (string.IsNullOrEmpty(propertyName))
return _errors.SelectMany(e => e.Value);
return _errors.TryGetValue(propertyName, out var errors) ? errors : Enumerable.Empty();
}

private void OnErrorsChanged(string propertyName) =>
ErrorsChanged?.Invoke(this, new DataErrorsChangedEventArgs(propertyName));

[RelayCommand(CanExecute = nameof(CanRegister))]
public void Register()
{
MessageBox.Show("注册成功");
}

public bool CanRegister() => !HasErrors;
}
#endregion
}

效果如下：

源代码地址如下：https://gitee.com/chenshibao/wpfdemo.git

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