C ivalueconverter interface usage example

01

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Introduce

IValueConverter The interface is in the namespace System.Windows.Data, Interface defined Convert and ConvertBack Two sets of methods ：

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

When the data type or format required by the interface control is inconsistent with the data bound in the background , It is often necessary to resort to IValueConverter Interface .

02

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give an example

•    Add a table control to the interface datagrid, Binding data structure StudentList,StudentList This is a ObservableCollection<Students> aggregate ;

• Students The data model is defined as follows ： It rewrites ToString Method , Four attributes are defined , Namely Id,Name ,Age and AgeValidate ,AgeValidate To validate data , I.e. younger than 16 Or greater than 21, The interface font displays red

• 

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•  [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();        }    }

Interface foreground binding ： Mainly through this sentence

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

datagrid The full code is as follows ：

 <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>

Define resources

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

• IValueConverter Interface implementation ： Note that the object Type of value Convert to our target type bool The amount

  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();        }    }

03

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Run Demo

Project source code

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