Binding row ObservableCollection

Question

Good morning

I'm trying to display two fields of an object on a label within a CollectionView.
The problem I have is that I don't know how I can bind the object so I can concatenate the fields I need into a custom converter.

a code example for a better understanding of the problem

                    <CollectionView 
                    ItemsSource="{Binding Purchases}"
                        >
                        <CollectionView.ItemTemplate>
                            <DataTemplate>
                                    <Grid>
                                        <Grid.ColumnDefinitions>
                                            <ColumnDefinition Width="0.65*"/>
                                            <ColumnDefinition Width="0.35*"/>
                                        </Grid.ColumnDefinitions>
                                        <Grid.RowDefinitions>
                                            <RowDefinition Height="*"/>
                                            <RowDefinition Height="*"/>
                                        </Grid.RowDefinitions>
                                    <Label Grid.Column="0" Grid.Row="0" Text="{Binding ??????, Converter={StaticResource PurchaseNameAndPriceConverter}}" ></Label>
                                </Grid>
                            </DataTemplate>
                        </CollectionView.ItemTemplate>
                    </CollectionView>


    class PurchaseNameAndPriceConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            Purchase p = (Purchase)value;
            return p.SellerName + p.Total.ToString() + " €";

        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }

I tried to bind with Binding (dot) but in the converter the object does not arrive,
I've been looking for information about this and I haven't found anything.

Could someone help me about this?

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

You could add . for this binding like following layout.

   <?xml version="1.0" encoding="utf-8" ?>  
   <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"  
                xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"   
                xmlns:local="clr-namespace:App70"  
                x:Class="App70.MainPage">  
       <ContentPage.Resources>  
           <ResourceDictionary>  
               <local:PurchaseNameAndPriceConverter x:Key="MyPurchaseNameAndPriceConverter" />  
           </ResourceDictionary>  
       </ContentPage.Resources>  
       <StackLayout>  
           <CollectionView   
                        ItemsSource="{Binding Purchases}"  
                            >  
               <CollectionView.ItemTemplate>  
                   <DataTemplate>  
                       <Grid>  
                           <Grid.ColumnDefinitions>  
                               <ColumnDefinition Width="0.65*"/>  
                               <ColumnDefinition Width="0.35*"/>  
                           </Grid.ColumnDefinitions>  
                           <Grid.RowDefinitions>  
                               <RowDefinition Height="*"/>  
                               <RowDefinition Height="*"/>  
                           </Grid.RowDefinitions>  
                           <Label Grid.Column="0" Grid.Row="0" Text="{Binding . , Converter={StaticResource MyPurchaseNameAndPriceConverter}}" ></Label>  
                       </Grid>  
                   </DataTemplate>  
               </CollectionView.ItemTemplate>  
           </CollectionView>  
       </StackLayout>  
     
   </ContentPage>  

In the background code. Please do not forget to add this.BindingContext = new MyViewModel();;

And you must change your code in PurchaseNameAndPriceConverter.cs, because ValueConverter will execute many times, we should judge the value of object value

   class PurchaseNameAndPriceConverter : IValueConverter  
       {  
           public object Convert(object value, Type targetType, object parameter, CultureInfo culture)  
           {  
               if (value!=null)  
               {  
                   Purchase p = (Purchase)value;  
                   return p.SellerName + p.Total.ToString() + " €";  
               }  
     
               return "";  
           }  
     
           public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)  
           {  
               // throw new NotImplementedException();  
     
               return value;  
           }  
       }  
   }  

Here is my test MyViewModel.cs.

   using System;  
   using System.Collections.Generic;  
   using System.Collections.ObjectModel;  
   using System.Text;  
     
   namespace App70  
   {  
       public class MyViewModel  
       {  
           public  ObservableCollection<Purchase> Purchases { get; set; }  
           public MyViewModel()  
           {  
               Purchases = new ObservableCollection<Purchase>();  
               Purchases.Add(new Purchase() { SellerName="name1", Total=12 });  
               Purchases.Add(new Purchase() { SellerName = "name2", Total = 15 });  
               Purchases.Add(new Purchase() { SellerName = "name3", Total = 11 });  
               Purchases.Add(new Purchase() { SellerName = "name4", Total = 13 });  
           }  
       }  
     
       public class Purchase  
       {  
           public string SellerName { get; set; }  
     
           public int Total { get; set; }  
       }  
   }  

Here is running screenshot.

Best Regards,

Leon Lu

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