I can't change property of a button....

Question

Hello,

I wrote a small app has 1 datepicker, 2 textboxes, 2 buttons.

here's the XAML code for app UI:

<Window x:Class="WpfApp3.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:WpfApp3"
        xmlns:model ="clr-namespace:WpfApp3.Model"
        xmlns:viewModel ="clr-namespace:WpfApp3.ViewModel"
        mc:Ignorable="d"
        Background="AliceBlue"
        ResizeMode="NoResize"
        Title="MainWindow" Height="400" Width="350">
    <Window.DataContext>
        <viewModel:MainViewModel/>
    </Window.DataContext>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="1.5*"/>
            <RowDefinition Height="1.5*"/>
            <RowDefinition Height="1.5*"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid Grid.Row="0">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="1.8*"/>
            </Grid.ColumnDefinitions>
            <TextBlock Grid.Column="0" x:Name="Date" Text="Date:" FontSize="20" FontWeight="Bold"  Margin="10,10,10,10" HorizontalAlignment="Center" VerticalAlignment="Center"/>
            <DatePicker x:Name="getdate" SelectedDate="{Binding SelectedDate}" Grid.Column="1" Width="200" Height="20" Margin="10,10,10,10" />
        </Grid>
        <Grid Grid.Row="1">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="1.8*"/>
            </Grid.ColumnDefinitions>
            <TextBlock Grid.Column="0" x:Name="Item" Text="Item:" FontSize="20" FontWeight="Bold" Margin="10,40,10,40" HorizontalAlignment="Center" VerticalAlignment="Center"/>
            <TextBox Grid.Column="1" FontSize="14" Text="{Binding Item}" Margin="10,40,10,40"/>
        </Grid>
        <Grid Grid.Row="2">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="1.8*"/>
            </Grid.ColumnDefinitions>
            <TextBlock Grid.Column="0" x:Name="Amount" Text="Amount:" FontSize="20" FontWeight="Bold" Margin="10,40,10,40" HorizontalAlignment="Center" VerticalAlignment="Center"/>
            <TextBox Grid.Column="1" FontSize="14" Text="{Binding Amount}"   Margin="10,40,10,40"/>
        </Grid>
        <Grid Grid.Row="3">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <Button Grid.Column="0" Content="ShowInput" Command="{Binding getInputCommand}" FontSize="14" FontWeight="Bold" Margin="20,10,20,10"/>
            <Button Grid.Column="1" Content="Clear" FontSize="14" Command="{Binding ClearCommand}" FontWeight="Bold" Margin="20,10,20,10"/>

        </Grid>
    </Grid>
</Window>

I run this code for the test but I got an error like this:

I checked "isEnabled" property for the button to true several times but I couldn't save it.

if someone help me to fix this, I'd be very appreciated.

thanks,

c00012