C# IValueConverter接口用法举例

 

01

—

 

 

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。

 

02

—

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();
          }
      }
  

  　

  项目源码

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