How can I convert Comboboxitem into string?

Question

Hello,

I have a combobox with enum source. I want to show selected combobox item in messagebox using MVVM and WPF.
Here's a code :

enum:

public enum ProdCode  
{  
    [Description("PersonalLoan")]  
    PersonalLoan,  
    [Description("Mortgage")]  
    Mortgage,  
    [Description("AutoLoan")]  
    AutoLoan  
};   

ICommand Interface:

   using System;  

using System.Windows.Controls;
using System.Windows.Input;

namespace WpfApp6.ViewModel
{
class MyCommand : ICommand
{
public event EventHandler CanExecuteChanged;

    private Action<ComboBoxItem>_execute;  

    public MyCommand(Action<ComboBoxItem> execute)  
    {  
        _execute=execute;  
    }  
      
    public bool CanExecute(object parameter)=>true;  

    public void Execute(object parameter)  
    {  
        var value= parameter as ComboBoxItem;  
        _execute.Invoke(value);  
    }  
}  

}

ViewModel:

   using System.Windows.Controls;  

using System.Windows.Input;

namespace WpfApp6.ViewModel
{
class MyViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;

    public ICommand ProdNavCommand { get; set; }  

    //private Enum _selectedItem;  
    private ComboBoxItem _selectedItem;  
    public ComboBoxItem SelectedItem  
    {  
        get=>_selectedItem;  
        set  
        {  
            _selectedItem= value;  
            OnPropertyChanged(nameof(SelectedItem));  
        }  
    }  

    private void OnPropertyChanged(string propertyName)  
    {  
        if(PropertyChanged!=null)  
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));  
    }  

    public MyViewModel()  
    {  
        ProdNavCommand=new MyCommand((SelectedItem)=>MessageBox.Show(string.Format("You select:" + SelectedItem),"Goes to..."));  
    }  
}  

}
Result of above code:

I tried to fix error but I couldn't even the cause of it. somebody give me an advice, I would be very appreciated.

thanks,

c00012

Answer 1

Hi,
try following demo based on your code::

XAML:

<Window x:Class="WpfApp1.Window063"  
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"  
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"  
        xmlns:local="clr-namespace:WpfApp063"  
        xmlns:sys="clr-namespace:System;assembly=mscorlib"  
        mc:Ignorable="d"  
        Title="Window063" Height="450" Width="800">  
  <Window.DataContext>  
    <local:MyViewModel/>  
  </Window.DataContext>  
  <Window.Resources>  
    <ObjectDataProvider x:Key="Codes"   
                        MethodName="GetValues"   
                        ObjectType="{x:Type sys:Enum}">  
      <ObjectDataProvider.MethodParameters>  
        <x:Type TypeName="local:ProdCode"/>  
      </ObjectDataProvider.MethodParameters>  
    </ObjectDataProvider>  
    </Window.Resources>  
    <StackPanel>  
    <ComboBox ItemsSource="{Binding Source={StaticResource Codes}}"  
              SelectedItem="{Binding SelectedItem}"/>  
    <Button Command="{Binding ProdNavCommand}" Content="Check"/>  
  </StackPanel>  
</Window>  

And code:

using System;  
using System.ComponentModel;  
using System.Windows;  
using System.Windows.Controls;  
using System.Windows.Input;  

namespace WpfApp063  
{  
  public class MyViewModel : INotifyPropertyChanged  
  {  
    public event PropertyChangedEventHandler PropertyChanged;  
    public ICommand ProdNavCommand { get; set; }  
    public ProdCode SelectedItem { get; set; }  
    private void OnPropertyChanged(string propertyName) =>  
       PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));  
    public MyViewModel()  
    {  
      ProdNavCommand = new MyCommand((state) => MessageBox.Show(string.Format("You select: " + SelectedItem), "Goes to..."));  
    }  
  }  

  public enum ProdCode  
  {  
    [Description("PersonalLoan")]  
    PersonalLoan,  
    [Description("Mortgage")]  
    Mortgage,  
    [Description("AutoLoan")]  
    AutoLoan  
  }  

  class MyCommand : ICommand  
  {  
    public event EventHandler CanExecuteChanged;  
    private Action<ComboBoxItem> _execute;  
    public MyCommand(Action<ComboBoxItem> execute) => _execute = execute;  
    public bool CanExecute(object parameter) => true;  
    public void Execute(object parameter)  
    {  
      var value = parameter as ComboBoxItem;  
      _execute.Invoke(value);  
    }  
  }  
}  

Result:

]1

Answer 2

You need update two places for your MyViewModel
1. Replace your ComboBoxItem SelectedItem with ProdCode SelectedItem like below:

 private ProdCode _selectedItem;  
        public ProdCode SelectedItem  
        {  
            get => _selectedItem;  
            set  
            {  
                _selectedItem = value;  
                OnPropertyChanged(nameof(SelectedItem));  
            }  
        }  

2. Replace the contents of the constructor as:

ProdNavCommand = new MyCommand((x) => MessageBox.Show(string.Format("You select:" + SelectedItem), "Goes to..."));  

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