Window.Resource not recognized in wpf aplication

Question

I´m new with WPF and the MVVM pattern, i have a view with 2 ComboBox, 1 Datapicker, 1 textbox and 1button, the intention is when i hit the button i obtain the data from this view in the ViewModel, to try this i've been based on this question in StackOverflow: https://stackoverflow.com/questions/27447042/xaml-button-comand-to-pass-to-date-picker-properties-to-method

The problema is that in the XAML in

Window.Resources PedidosRetraso:ICommandMultiDateConverter x:Key="multiDateConverter"/>

Give me an error, NameSpace prefix "PedidosRetraso" not defined, and i don´t know why, the name of the namespace is correct,¿What i´m doing wrong?.

Also I would like to know how i can verify that the ComboBox have some value selected to disable the button in case of not selected value, i think i shoul do it in CanExecute but i dont know how i know the value of the ComboBox.

This is my XAML code

<Window x:Class="PedidosRetraso.MainWindow"
    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:PedidosRetraso"
    mc:Ignorable="d"
    Title="MainWindow" Height="700" Width="700"
    >
<Window.Resources>
    <PedidosRetraso:ICommandMultiDateConverter x:Key="multiDateConverter"/>
</Window.Resources>

<Grid>

    <ComboBox x:Name="comboBox" HorizontalAlignment="Left" Margin="22,59,0,0" VerticalAlignment="Top" Width="120" SelectionChanged="comboBox_SelectionChanged">
    </ComboBox>
    <Button x:Name="button" Content="Button" HorizontalAlignment="Left" Margin="573,66,0,0" VerticalAlignment="Top" Width="75" >
        <Button.CommandParameter>
            <MultiBinding Converter="{StaticResource ResourceKey=multiDateConverter}">
                <Binding ElementName="textBox" Path="Text"></Binding>
                <Binding ElementName="comboBox" Path="Text"></Binding>
                <Binding ElementName="comboBox1" Path="Text"></Binding>
                <Binding ElementName="Fecha" Path="Text"></Binding>
            </MultiBinding>
        </Button.CommandParameter>
        <Button.Command>
            <Binding Path="GetAllActionLogsBetweenDatesCommand"></Binding>
        </Button.Command>
    </Button>
    <ComboBox x:Name="comboBox1" HorizontalAlignment="Left" Margin="183,59,0,0" VerticalAlignment="Top" Width="120" ItemsSource="{Binding _combo}">
        <ComboBox.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Horizontal">
                    <TextBlock Text="Situación: "></TextBlock>
                    <TextBlock Text="{Binding Path=Nombre}" Width="80"></TextBlock>
                </StackPanel>
            </DataTemplate>
        </ComboBox.ItemTemplate>

    </ComboBox>

And this is my ViewModel:

public class RelayCommand : ICommand
{
    private Predicate<object> m_canExecute;
    private Action<object> m_execute;

    public RelayCommand(Action<object> execute)
    {
        m_execute = execute;
    }

    public RelayCommand(Predicate<object> canExecute, Action<object> execute)
    {
        m_canExecute = CanExecute;
        m_execute = execute;
    }

    public bool CanExecute(object parameter)
    {
        if (m_canExecute == null)
        {
            return true;
        }

        return m_canExecute(parameter);
    }

    public event EventHandler CanExecuteChanged;

    public void Execute(object parameter)
    {
        if (m_execute != null)
        {
            m_execute(parameter);
        }
    }
}

public class ICommandMultiDateConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return new string[] { values[0].ToString(), values[1].ToString(), values[2].ToString(),values[3].ToString() };
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

class ViewModelMain 
{
    public ICommand GetAllActionLogsBetweenDatesCommand { get; set; }

    public ObservableCollection<PocoCombo> _combo { get; set; }
   public ViewModelMain()
    {
        GetAllActionLogsBetweenDatesCommand = new RelayCommand(GetAllActionLogsBetweenDates_Execute);

        _combo = new ObservableCollection<PocoCombo> { new PocoCombo { Id = 20, Nombre = "Enviado" }, new PocoCombo { Id = 25, Nombre = "DIF" }, new PocoCombo { Id = 30, Nombre = "Confirmado" }, new PocoCombo { Id = 40, Nombre = "RP" }, new PocoCombo { Id = 50, Nombre = "Cerrado" }, new PocoCombo { Id = 60, Nombre = "C" } };
   }


  private void GetAllActionLogsBetweenDates_Execute(object parameter)
    {
        try
        {
            var stringList = parameter as string[];

            string proveedor = stringList[0];
            string empresa = stringList[1];
            string situacion = stringList[2];
            DateTime fecha = DateTime.Parse(stringList[3]);
            // Aqui la consulta SQL
        }
        catch (Exception ex)
        {

        }
    }

EDIT i put a photo

Thanks.

Answer 1

You have defined the namespace here xmlns:local="clr-namespace:PedidosRetraso", so use it!

Change

<PedidosRetraso:ICommandMultiDateConverter x:Key="multiDateConverter"/>

To

<local:ICommandMultiDateConverter x:Key="multiDateConverter"/>

EDIT

You have added a picture. ICommandMultiDataConverter isn't in namespace PedidosRetraso as I thought but PedidosRetraso.viewModel

Change xmlns:local="clr-namespace:PedidosRetraso" to xmlns:local="clr-namespace:PedidosRetraso.viewModel"