浅谈WPF之Binding时数据校验和类型转换
在WPF开发中，Binding实现了数据在Source和Target之间的传递和流通，就像现实生活中的一条条道路，建立起了城镇与城镇之间的衔接，而数据校验和类型转换，就像高速公路之间的收费站和安检站。那在WPF开发中，如何实现数据的校验和类型转换呢？本文以一个简单的小例子，简述在WPF开发中，实现数据校验和类型转换的相关知识点，仅供学习分享使用，如有不足之处，还请指正。在数据绑定Binding中，数据校验主要通过ValidationRules属性，数据转换主要通过Converter属性。
数据校验
在WPF开发中，校验数据的有效性，主要步骤如下：
1. 实现校验规则
Binding的ValidationRules是Collection类型，是一个校验规则列表，可以支持多重校验。而ValidationRule是一个抽象类，所有要实现业务规则校验，就要继承ValidationRule并实现抽象方法。
ValidationRule的Validate方法返回一个ValidationResult对象，如果校验通过，则ValidationResult的IsValid为true，否则为false。RangeValidationRule主要校验用户输入数据的范围：
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Controls;
namespace WpfApp4.DataValidate
{
public class RangeValidationRule : ValidationRule
{
public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
double d = 0;
if(double.TryParse(value.ToString(),out d))
{
if(d>=0 && d <= 100)
{
return new ValidationResult(true,null);
}
}
return new ValidationResult(false, "数据必须在0~100之间");
}
}
}
4. 数据校验示例演示
经过上述步骤，运行程序，如下所示：
数据类型转换
在数据绑定时，如果Source端的数据类型和Target端的数据类型不一致时，就需要用到数据类型转换，如：true/false与显示/隐藏之间的转换等，要实现数据转换，需要用到Binding的Converter属性。步骤如下：
1. 定义转换器
Binding的Converter属性是IValueConverter类型，所以定义转换器需要实现IValueConverter接口，如下所示：
<TextBlock Text="年龄" VerticalAlignment="Center"></TextBlock>
<TextBox x:Name="tbAge" Width="120" Height="25" Margin="10" Validation.Error="tbAge_Error" VerticalContentAlignment="Center">
private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}<TextBox.Text>
private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}<Binding Path="Age" UpdateSourceTrigger="PropertyChanged" NotifyOnValidationError="True">
private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}<Binding.ValidationRules>
private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}<v:RangeValidationRule ValidatesOnTargetUpdated="True"></v:RangeValidationRule>
private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}</Binding.ValidationRules>
private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}</Binding>
private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}</TextBox.Text>
</TextBox>
<TextBlock VerticalAlignment="Center" Text="{Binding DataError}" Foreground="Red"></TextBlock>注意：IValueConverter接口共两个方法，其中Convert方法当Source到Target时调用，ConvertBack方法则是反方向调用。
2. 定义资源
转换器也是一种资源，要声明资源，首先引入命名空间xmlns:c="clr-namespace:WpfApp4.DataConverter"，如下所示：
private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}
3. 调用类型转换
在Binding时，调用资源Visibility="{Binding ElementName=chk01, Path=IsChecked, Converter={StaticResource boolToVisility}}"。通过复选框的选择与否，控制控件的显示与隐藏，如下所示：
private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}private void tbAge_Error(object sender, ValidationErrorEventArgs e)
{
this.viewModel.ValidationErrorCommand.Execute(e);
}
4. 数据类型转换示例演示
源码下载
本实例源码相对简单，如果需要源码下载，可关注公众号，回复关键字DATAVC进行获取，如下所示：
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来源:https://www.cnblogs.com/hsiang/p/18050883
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