Winforms数据绑定：可以使用TypeConverter而不是Format / Parse事件吗？ [英] Winforms data binding: Can a TypeConverter be used instead of the Format/Parse events?

问题描述

在Winforms表单中，当输入字段包含无效值时，我想向用户提供视觉提示。为此，我想将输入字段标签的 ForeColor 属性绑定到（布尔） IsPropertyValid 属性底层模型使得当 IsPropertyValid == false 时，标签变红。

我目前拥有的是一个事件绑定的格式的处理程序事件：

 控件[dateOfBirthLabel] .DataBindings [ForeColor]。格式+ = convertBoolToColor; 
 //（dateOfBirthLabel.ForeColor绑定到一个布尔型IsDateOfBirthValid属性）
 
 void convertBoolToColor（object sender，ConvertEventArgs e）
 {
 e.Value =（ bool）e.Value？ Color.Black：Color.Red; 
} 
  

如果我想在WPF中这样做，我想我会指定一个自定义价值转换器（ bool 至颜色）直接与XAML中的绑定。最重要的是，我不必通过其名称来引用具体的控件。

我想和我做同样的事情Winforms形式。理想情况下，我可以在Forms Designer中直接指定特定绑定的 TypeConverter 对象。这是可能吗？

解决方案

我的以前的答案（现已删除）不正确：可以使用 .componentmodel.typeconverter.aspxrel =nofollowtitle =System.ComponentModel.TypeConverter的MSDN参考页面> TypeConverter 。

首先，需要一个合适的转换器。 （与XAML不同，没有实现 IValueConverter ，但是从 TypeConverter ）例如：

  // using System; 
 // using System.ComponentModel; 
 //使用System.Drawing; 
 //使用System.Globalization; 
 
密码类BooleanToColorConverter：TypeConverter 
 {
 public override bool CanConvertTo（ITypeDescriptorContext context，
 Type destinationType）
 {
 return destinationType == typeof（Color）; 
 
 
 public override object ConvertTo（ITypeDescriptorContext context，
 CultureInfo culture，
 object value，
 Type destinationType）
 {
返回（bool）值？ Color.Green：Color.Red; 
} 
} 
  

接下来也不同于XAML数据绑定，）该转换器不适用于绑定本身;它必须使用 [TypeConverter] 属性：

  // using System.ComponentModel; 
 
 partial class DataSource：INotifyPropertyChanged 
 {
 [TypeConverter（typeof（BooleanToColorConverter））] //<  - 添加这个！ 
 public bool IsValid {get {...} set {...}} 
} 
  

最后，的MSDN参考页面

  //控制控件= ...; 
 // DataSource dataSource = ...; 
 
 control.DataBindings.Add（ForeColor，dataSource，IsValid，formattingEnabled：true）; 
 // ^^^^^^^^^^^^^^^^^^^^^^ 
  

请注意，此示例仅涉及单向（数据源来控制）数据绑定。对于双向数据绑定，您还需要覆盖 TypeConverter.ConvertFrom 和 TypeConverter.CanConvertFrom 方法。 / p>

In a Winforms form, I want to provide visual cues to the user when an input field contains an invalid value. To that end, I want to bind the ForeColor property of a input field's label to the (boolean) IsPropertyValid property of the underlying model such that the label turns red when IsPropertyValid == false.

What I currently have is an event handler for the binding's Format event:

Controls["dateOfBirthLabel"].DataBindings["ForeColor"].Format += convertBoolToColor;
// (dateOfBirthLabel.ForeColor is bound to a boolean IsDateOfBirthValid property.)

void convertBoolToColor(object sender, ConvertEventArgs e)
{
    e.Value = (bool)e.Value ? Color.Black : Color.Red;
}

If I wanted to do this in WPF, I suppose I would specify a custom value converter (bool to Color) directly with the binding in the XAML. Most importantly, I wouldn't have to refer to a specific control via its name.

I would like to do the same thing with my Winforms form. Ideally, I could specify a TypeConverter object for a particular binding directly in the Forms Designer. Is this possible?

解决方案

My previous answer (now deleted) was incorrect: This can be done, using a custom TypeConverter.

First, one needs a suitable converter. (Unlike with XAML, one does not implement a IValueConverter, but derive from TypeConverter.) For example:

// using System;
// using System.ComponentModel;
// using System.Drawing;
// using System.Globalization;

sealed class BooleanToColorConverter : TypeConverter
{
    public override bool CanConvertTo(ITypeDescriptorContext context,
                                      Type destinationType)
    {
        return destinationType == typeof(Color);
    }

    public override object ConvertTo(ITypeDescriptorContext context,
                                     CultureInfo culture,
                                     object value, 
                                     Type destinationType)
    {
        return (bool)value ? Color.Green : Color.Red;
    }
}

Next, (and also unlike with XAML data binding,) this converter is not applied to the binding itself; it must be attached to the data source's property using the [TypeConverter] attribute:

// using System.ComponentModel;

partial class DataSource : INotifyPropertyChanged
{
    [TypeConverter(typeof(BooleanToColorConverter))] // <-- add this! 
    public bool IsValid { get { … } set { … } }
}

Finally, formatting must be enabled on the data binding:

// Control control = …;
// DataSource dataSource = …;

control.DataBindings.Add("ForeColor", dataSource, "IsValid", formattingEnabled: true);
//                                                           ^^^^^^^^^^^^^^^^^^^^^^^

Note that this example only deals with one-way (data source to control) data binding. For two-way data binding, you would additionally have to override the TypeConverter.ConvertFrom and TypeConverter.CanConvertFrom methods.

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