Table of Contents


Introduction


In some cases, we might have several fields in your data model that represent a name (first name, middle name and last name) that you want to combine into a single entry in a list. MultiBinding takes multiple values and combines them into another value. There are two ways to do MultiBinding, either using StringFormat or by a converter. The StringFormat is simple compared to a converter, so we will start with that first.

MultiBinding: Using StringFormat



<TextBlock> 
   <TextBlock.Text> 
   <MultiBinding StringFormat=" {0}, {1}, {2}"> 
   <Binding ElementName="ThisWindow" Path="FirstName"/> 
   <Binding ElementName="ThisWindow" Path="MiddleName"/> 
   <Binding ElementName="ThisWindow" Path="LastName"/> 
   </MultiBinding> 
   </TextBlock.Text> 
</TextBlock>

Here the {0} ,{1}, {2} values will be replaced at runtime with FirstName, MiddleName, LastName.

MultiBinding: Using Converter



The converter must be derived from IMultiValueConverter and is very similar to a converter derived from IValueConverter, except that instead of having a single value as an argument, it takes multiple arguments.

public class TotalConverter : IMultiValueConverter 
    { 
   
        public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture) 
        { 
            decimal Amount = 0; 
            decimal Discount = 0; 
            string TotalAmount = string.Empty; 
            Amount = (values[0] != null && values[0] != DependencyProperty.UnsetValue) ? System.Convert.ToDecimal(values[0]) : 0; 
            Discount = (values[0] != null && values[1] != DependencyProperty.UnsetValue) ? System.Convert.ToDecimal(values[1]) : 0; 
            TotalAmount = System.Convert.ToString(Amount - Discount); 
          return TotalAmount;  
        } 
   
        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture) 
        { 
            throw new NotImplementedException(); 
        } 
    }

Here in the value field, we will get multiple values (amount and discount), after the conversation the single value will be returned.

Now we have a MultiValueConverter, we need to create an instance of it in a XAML resource.

xml code


We put in the main Window tag to remind you to put in the converter namespace. Then we instantiate the converter as a resource with a name. Now we can do our MultiBinding.

<TextBox Margin="2" MinWidth="120" Grid.Row="1" Grid.Column="1"> 
            <TextBox.Text> 
                <MultiBinding Converter="{StaticResource Totalconverter }"> 
                    <Binding Path="Amount"   ElementName="ThisWindow"/> 
                    <Binding Path="Discount"  ElementName="ThisWindow"/> 
                </MultiBinding> 
            </TextBox.Text> 
        </TextBox>


Here we have the two properties (Amount and Discount), these properties are bound to the TextBox and implemented TotalConverter.

public partial class MainWindow : Window, INotifyPropertyChanged 
    { 
        public MainWindow() 
        { 
            InitializeComponent(); 
        } 
        private decimal amount ; 
   
        public decimal Amount 
        { 
            get { return amount; } 
            set { amount = value; 
            OnPropertyChanged("Amount"); 
            } 
        } 
        private decimal discount; 
   
        public decimal Discount 
        { 
            get { return discount; } 
            set { discount = value; 
            OnPropertyChanged("Discount"); 
            } 
        }        
          
  
        #region INotifyPropertyChanged Members implementation 
   
        public event PropertyChangedEventHandler PropertyChanged; 
        public void OnPropertyChanged(string txt) 
        { 
   
            PropertyChangedEventHandler handle = PropertyChanged; 
            if (handle != null) 
            { 
                handle(this, new PropertyChangedEventArgs(txt)); 
            } 
        } 
        #endregion 
    }


That's it. Run the application.

http://www.c-sharpcorner.com/UploadFile/91c28d/multibinding-and-imultivalueconverter-in-wpf/Images/mainwin1.jpg

Figure: Initial state


entervalue


Figure: Amount = 2 and Discount = 0. So Amount – Discount = Total = 2

mainwin


Figure: Amount = 223413 and Discount = 0. So Amount – Discount = Total = 223413


mainwindowenter


Figure: Amount = 223413 and Discount = 564554544. So Amount – Discount = Total = -564331131 

Downloads: Multibinding


See Also


Data Binding Overview