【原】C# IValueConverter接口用法举例

ontheroad96j47 2022-01-30

展开全文

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介绍

IValueConverter接口位于名称空间System.Windows.Data，接口定义了Convert和ConvertBack两组方法：

    public interface IValueConverter    {        object Convert(object value, Type targetType, object parameter, CultureInfo culture);        object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture);    }}

在界面控件所需数据类型或格式和后台绑定的数据不一致时，往往需要借助IValueConverter接口进行转换。

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举例

界面添加一个表格控件datagrid，绑定数据结构StudentList，StudentList这是一个ObservableCollection<Students>集合；
Students数据模型定义如下：其中重写了ToString方法，并定义了四个属性，分别是Id，Name ，Age 和AgeValidate ，AgeValidate 用来验证数据，即年龄小于16或者大于21,时界面字体显示红色

 [AddINotifyPropertyChangedInterface]    public class Students     {        private int id;        public int Id        {            get { return id; }            set            {                id = value;            }        }        public string Name { get; set; }
        private int age;        public int Age         {            get { return age; }            set            {                age = value;                if(age < 16 || age > 21 )                {                    AgeValidate = true;                }                else                {                    AgeValidate = false;                }            }        }
        public bool AgeValidate { get; set; }        public override string ToString()        {            StringBuilder report = new StringBuilder();            report.AppendLine($"[Id]  = [{Id}]");            report.AppendLine($"[Name]  = [{Name}]");            report.AppendLine($"[Age]  = [{Age}]");            report.AppendLine($"[AgeValidate]  = [{AgeValidate}]");            return report.ToString();        }    }

界面前台绑定：主要是通过这句

 Foreground="{Binding AgeValidate,Converter={StaticResource ShowColorConverter}}"

datagrid全部的代码如下：

 <DataGrid Name="dgSourceData" AutoGenerateColumns="False" ItemsSource="{Binding StudentList}"                   ContextMenu="{Binding menu1}" RowHeaderWidth="30"  SelectedItem ="{Binding SelectedItems}" SelectionMode="Single" SelectionUnit="Cell"                                cal:Message.Attach="[Event SelectionChanged]=[GridControl_SelectionChanged($source,$eventArgs)];"                                CellEditEnding="dgSourceData_BeginningEdit" SelectionChanged="dgSourceData_SelectionChanged" >            <DataGrid.Columns>                <DataGridTextColumn Header="Name"  Binding="{ Binding Path=Name}" MinWidth="68"/>                <DataGridTemplateColumn  Header="Age"  MinWidth="68" >                    <DataGridTemplateColumn.CellTemplate>                        <DataTemplate>                            <TextBox Text="{Binding Path=Age,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"                                      Foreground="{Binding AgeValidate,Converter={StaticResource ShowColorConverter}}" />                        </DataTemplate>                    </DataGridTemplateColumn.CellTemplate>                </DataGridTemplateColumn>                <DataGridTextColumn Header="Id"  Binding="{ Binding Path=Id}" MinWidth="48"/>            </DataGrid.Columns>        </DataGrid>

定义资源

    <UserControl.Resources>        <converters:ShowColorConverter x:Key="ShowColorConverter" />    </UserControl.Resources>

IValueConverter接口实现：注意需要将object类型的value转换为我们的目标类型bool量

public class ShowColorConverter : IValueConverter    {        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)        {            var flag = (bool)value;            if (flag)            {                return "Red";            }            else            {                return "Black";            }        }
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)        {            throw new NotImplementedException();        }    }