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Button visibility after enter value (XAML, C#, IValueConverter)

I have xaml file where I put 2 TextBox where I can put login and password. After then Button "Login" should be visible. Here is my code:
TreeView.xaml file:
<UserControl x:Class="LayoutMVVM.Views.TreeView"
xmlns:local="clr-namespace:LayoutMVVM.Views"
xmlns:Treemodels="clr-namespace:LayoutMVVM.ViewModels" .../>
<UserControl.Resources>
<Treemodels:VBConverter x:Key="VBConverter" />
</UserControl.Resources>
<Grid>
....
<TextBox Grid.Row="2" Grid.Column="2" Text="{Binding Login, UpdateSourceTrigger=PropertyChanged}" Background="AliceBlue" />
<TextBox Grid.Row="1" Grid.Column="2" Text="{Binding Password, UpdateSourceTrigger=PropertyChanged}" Background="AliceBlue" />
<Button Grid.Row="3" Grid.Column="3" Visibility="{Binding IsVerifyTrue, Converter={StaticResource VBConverter}}" Content="Login" />
</Grid>
TreeView.xaml.cs
namespace LayoutMVVM.Views
{
public partial class TreeView : UserControl
{
public TreeView()
{
InitializeComponent();
}
public TreeView _isVerifyTrue;
public TreeView IsVerifyTrue
{
get { return this; }
set
{
_isVerifyTrue = value;
OnPropertyChanged(() => IsVerifyTrue);
}
}
private void OnPropertyChanged(Func<object> p)
{
throw new NotImplementedException();
}
private string _login;
public string Login
{
get { return _login; }
set
{
_login = value;
IsVerifyTrue = this;
OnPropertyChanged(() => Login);
}
}
private string _password;
public string Password
{
get { return _password; }
set
{
_password = value;
IsVerifyTrue = this;
OnPropertyChanged(() => Password);
}
}
}
and seperate class for VBConverter.cs:
namespace LayoutMVVM.ViewModels
{
public class VBConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is TreeView)
{
var tv = value as TreeView;
bool result = !string.IsNullOrEmpty(tv.Login)
&& !string.IsNullOrEmpty(tv.Password);
return result? Visibility.Visible : Visibility.Hidden;
}
return Visibility.Hidden;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
When I start app button is always visible and I'm not know what is wrong.

You'll need a MultiValueConverter for this. See below example :
XAML :
<Window x:Class="SOSample1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:SOSample1"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Grid.Resources>
<local:VisibilityConverter x:Key="VisibilityConverter" />
</Grid.Resources>
<Grid.RowDefinitions>
<RowDefinition Height="100" />
<RowDefinition Height="100" />
<RowDefinition Height="100" />
</Grid.RowDefinitions>
<TextBox Grid.Row="0" Name="user" Height="100" Width="200" Text="{Binding Login, UpdateSourceTrigger=PropertyChanged}" Background="AliceBlue" />
<TextBox Grid.Row="1" Name="password" Height="100" Width="200" Text="{Binding Login, UpdateSourceTrigger=PropertyChanged}" Background="AliceBlue" />
<Button Grid.Row="2" Content="Login" Height="100" Width="200" >
<Button.Visibility>
<MultiBinding Converter="{StaticResource VisibilityConverter}" >
<Binding ElementName="user" Path="Text" />
<Binding ElementName="password" Path="Text" />
</MultiBinding>
</Button.Visibility>
</Button>
</Grid>
Converter :
public class VisibilityConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
bool result = false;
if (values != null)
{
foreach (var item in values)
{
result = (item as string).Length > 0;
if (!result) break;
}
}
return (Visibility)new BooleanToVisibilityConverter().Convert(result, targetType, parameter, culture);
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
{
return null;
}
}
OUTPUT

Using ObjectDataProvider inside HierarchicalDataTemplate

I want to add items of my class treeviewitem to a TreeView.
And I want to bind the ItemSource of this TreeViewItem to a method of itself !
I am trying to use the ObjectDataProvider for this.. See my XAML:
<Grid Background="#FFE5E5E5">
<Grid.Resources>
<HierarchicalDataTemplate DataType="{x:Type myNs:treeviewitem}">
<HierarchicalDataTemplate.Resources>
<ObjectDataProvider x:Key="getItems"
MethodName="GetItems"
ObjectInstance="{Binding RelativeSource={RelativeSource Self}}" />
</HierarchicalDataTemplate.Resources>
<HierarchicalDataTemplate.ItemsSource>
<Binding Source="{StaticResource getItems}" />
</HierarchicalDataTemplate.ItemsSource>
<StackPanel Orientation="Horizontal">
<TextBlock Margin="5,0,0,0"
Text="{Binding Name}" />
</StackPanel>
</HierarchicalDataTemplate>
</Grid.Resources>
<TreeView x:Name="guiTreeview"
HorizontalAlignment="Left"
Width="200" />
</Grid>
But binding to an ObjectInstance isnt possible!
How is it possible to get the current object instance "into" the ObjectDataProvider?
What would be the right way of doint this?
And NO, its not possible to use a Property ..

I have done it now with a ValueConverter.
XAML:
<Grid Background="#FFE5E5E5">
<Grid.Resources>
<HierarchicalDataTemplate DataType="{x:Type myNs:MyItem}" ItemsSource="{Binding RelativeSource={RelativeSource Self}, Converter={myNs:GetItemsConverter}}" >
<StackPanel Orientation="Horizontal">
<TextBlock Margin="5,0,0,0" Text="{Binding Name}" />
</StackPanel>
</HierarchicalDataTemplate>
</Grid.Resources>
<TreeView x:Name="guiTreeview" HorizontalAlignment="Left" Width="200" />
</Grid>
Converter:
public abstract class BaseConverter : MarkupExtension
{
public override object ProvideValue(IServiceProvider serviceProvider)
{
return this;
}
}
public class GetItemsConverter : BaseConverter, IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
var tvi = value as TreeViewItem;
if (tvi == null) return null;
var myitem = tvi.DataContext as MyItem;
if (myitem == null) return null;
return myitem.GetItems();
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return null;
}
}

Binding of control visibility to ViewModel property doesn't work

I'm in the process of converting a fairly large WPF app from three-layer into MVVM, and in the process learning MVVM. So far, I haven't delved into too much detail around Bindings (etc), so bear with me.
I'm trying to bind the System.Windows.Visibility of multiple controls to a public property ("State") of the ViewModel. When the parent TabItem loads, the State property is read and handled as desired. When subsequent changes to the property are made, however, they appear to be ignored. I've (re-re-re-)checked Bindings, debugged the Converters, etc, and this is driving me crazy.
ViewModel:
public class MarketingListViewModel: IDisposable, INotifyPropertyChanged
{
private UiState state;
public event PropertyChangedEventHandler PropertyChanged;
public UiState State
{
get { return state; }
set
{
if (state != value)
{
state = value;
NotifyPropertyChanged("State");
}
}
}
public MarketingListViewModel()
{
State = UiState.View;
}
private void NotifyPropertyChanged(String info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
}
View:
<UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:diag="clr-namespace:System.Diagnostics;assembly=WindowsBase"
mc:Ignorable="d" x:Class="WpfCrm.tabListManager" xmlns:DPH="clr-namespace:DPH" >
<UserControl.Resources>
<DPH:MarketingListViewModel x:Key="listVM" />
<!-- Note that the above line is giving me an "Object reference not set to an instance of an object" error -->
</UserControl.Resources>
<Grid x:Name="gridMain" DataContext="{StaticResource listVM}" >
<Border Grid.Row="0" Grid.Column="1" Margin="10"
Style="{StaticResource WidgetStyle}" >
<Grid x:Name="gridListManagement" >
<Label x:Name="labelManageLists" Content="Manage Lists" MouseDown="labelManageLists_MouseDown"
Style="{StaticResource WidgetTitleStyle}"
Grid.Row="0" Grid.Column="0" />
<StackPanel Grid.Row="0" Grid.Column="2" Orientation="Horizontal" HorizontalAlignment="Right" >
<Label x:Name="llNewList" Content="new" MouseDown="llNewList_MouseDown"
Style="{StaticResource LinkLabelStyle}"
HorizontalAlignment="Right" />
<Label x:Name="llCloseManageLists" Content="close" MouseDown="llCloseManageLists_MouseDown"
Style="{StaticResource LinkLabelStyle}"
HorizontalAlignment="Right" />
</StackPanel>
<Label x:Name="labelListName" Content="Name" Grid.Row="1" Grid.Column="0" />
<Grid Grid.Row="1" Grid.Column="1" Grid.ColumnSpan="2" HorizontalAlignment="Stretch" >
<ComboBox x:Name="cbLists" SelectedIndex="-1" SelectionChanged="cbLists_SelectionChanged" IsReadOnly="True"
ItemsSource="{Binding Path=AllMarketingLists}"
DisplayMemberPath="Name"
SelectedValuePath="Id"
Visibility="{Binding Path=State, Converter={StaticResource ViewStateToVisibilityConverter} }"/>
<TextBox x:Name="tbListName"
Text="{Binding Path=OList.Name}"
Visibility="{Binding Path=State, Converter={StaticResource EditStateToVisibilityConverter} }"/>
</Grid>
<Label x:Name="labelListDescription" Content="Description" Grid.Row="2" Grid.Column="0" />
<Grid Grid.Row="2" Grid.Column="1" Grid.ColumnSpan="2" >
<TextBlock x:Name="textblockListDescription" TextWrapping="Wrap"
Text="{Binding Path=OList.Notes}"
Visibility="{Binding Path=State, Converter={StaticResource ViewStateToVisibilityConverter} }"
Grid.ColumnSpan="2" />
<TextBox x:Name="tbListDescription" TextWrapping="Wrap"
Text="{Binding Path=OList.Notes}"
Visibility="{Binding Path=State, Converter={StaticResource EditStateToVisibilityConverter} }"
Grid.ColumnSpan="2" />
</Grid>
<StackPanel Grid.Row="3" Grid.Column="0" Grid.ColumnSpan="3" HorizontalAlignment="Right" Orientation="Horizontal" >
<Button x:Name="buttonEditList" Content="Edit" Click="buttonEditList_Click"
Visibility="{Binding Path=State, Converter={StaticResource ViewStateToVisibilityConverter} }"
Width="60" Margin="3" />
<Button x:Name="buttonSaveList" Content="Save" Click="buttonSaveList_Click"
Visibility="{Binding Path=State, Converter={StaticResource EditStateToVisibilityConverter} }"
Width="60" Margin="3" />
<Button x:Name="buttonCancel" Content="Cancel" Click="buttonCancel_Click"
Visibility="{Binding Path=State, Converter={StaticResource EditStateToVisibilityConverter} }"
Width="60" Margin="3" />
</StackPanel>
</Grid>
</Border>
</Grid>
And the code-behind has a few methods like:
private void buttonEditList_Click(object sender, RoutedEventArgs e)
{
listVM.State = UiState.Edit;
}
Does anyone have ideas on why the controls aren't updating their visibility after the State change?
Kind thanks,
DPH
EDIT -- Converters:
[ValueConversion(typeof(WpfCrm.UiState), typeof(System.Windows.Visibility))]
public class EditStateToVisibilityConverter: IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
UiState state = (UiState)value;
if (state == UiState.View) return Visibility.Collapsed;
else return Visibility.Visible;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return null;
}
}
[ValueConversion(typeof(WpfCrm.UiState), typeof(System.Windows.Visibility))]
public class ViewStateToVisibilityConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
UiState state = (UiState)value;
if (state == UiState.View) return Visibility.Visible;
else return Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return null;
}
}

You seem to be used two different instances of your view model, one declared and used in XAML
<UserControl.Resources>
<DPH:MarketingListViewModel x:Key="listVM" />
</UserControl.Resources>
<Grid DataContext="{StaticResource listVM}" >
and one in code-behind (from comment):
listVM = new MarketingListViewModel();
You should of course be using only one. So change your code behind declaration to
listVM = (MarketingListViewModel)Resources["listVM"];

OK, there is a mistake. You declare listVM as
var listVM = new MarketingListViewModel();
But this is not the listVM from your XAML. In XAML you have created another instance of MarketingListViewModel. So, when you try to change listVM that was declared in code, nothing happens because this object is not DataContext of your Grid.
In your Click handler you have to write the following:
private void buttonEditList_Click(object sender, RoutedEventArgs e)
{
var _listVM = (MarketingListViewModel)FindResource("listVM");
_listVM.State = UiState.Edit;
}
OR replace your listVM declaration in code-behind with this one:
listVM = (MarketingListViewModel)FindResource("listVM");
Then you won't need to change event handlers.
Hope, it helps.

Passing values to IValueConverter

I have a ListView that has a Grid with two columns and many rows. Each row has a TextBlock in each column with each Text property binded to a value in ListView's ItemSource. I need to do some converting of the text in the second TextBlock depending on the value in the first TextBlock. How can I get the value of the first text box to the converter?
Here is what I have so far:
XAML:
<UserControl.Resources>
<local:ValueStringConverter x:Key="valueStringConverter" />
</UserControl.Resources>
<ListView Name="theListView" ItemsSource="{Binding ItemCollection}" SelectedItem="{Binding SelectedItem}" ScrollViewer.HorizontalScrollBarVisibility="Disabled" Grid.Row="1" >
<ListView.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding Path=Key}" Grid.Column="0" Margin="0,0,10,0" />
<TextBlock Text="{Binding Path=Value, Converter={StaticResource valueStringConverter}}" TextWrapping="Wrap" Grid.Column="1" />
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
Code of ValueStringConverter:
public class ValueStringConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
string name = (string)value;
name = name.Replace("$$", " ");
name = name.Replace("*", ", ");
name = name.Replace("##", ", ");
return value;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}

You can't pass more than one value to the "regular" value converter. You could go with IMultiValueConverter and define the binding as MultiBinding.
Or you can create a IValueConverter that takes the entire object in the DataContext, cast the object to its type, take the Value and Key and return the string you need.
On your second textblock define the binding as
<TextBlock Text="{Binding Converter={StaticResource valueStringConverter}"/>
And your converter as:
public class ValueStringConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
MyDataContextObjectType obj= (MyDataContextObjectType)value;
var name= obj.Name;
var key = obj.Key;
//here you have both Name and Key, build your string and return it
//if you don't know the type of object in the DataContext, you could get the Key and Name with reflection
name = name.Replace("$$", " ");
name = name.Replace("*", ", ");
name = name.Replace("##", ", ");
return value;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}

Try multi-binding. You'll need an IMultiValueConverter:
public class MultiValueConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
var key = (string)values[0];
var value = (string)values[1];
// replace with appropriate logic
var result = key + ": " + value;
return result;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
and slightly modified XAML:
<TextBlock Text="{Binding Path=Key}" Grid.Column="0" Margin="0,0,10,0" />
<TextBlock TextWrapping="Wrap" Grid.Column="1">
<TextBlock.Text>
<MultiBinding Converter={StaticResource valueStringConverter}>
<Binding Path="Key" />
<Binding Path="Value" />
</MultiBinding>
</TextBlock.Text>
</TextBlock>

Bind to the instance, not the property (value in this case). Then you will have access to both Key and Value in the converter.

How to get datacontext from stackpanel

I have:
<StackPanel DataContext="{Binding Path =MyContext}">
<TextBox Text="{Binding Path =Content}" x:Name="tbName" IsReadOnly="False">
</TextBox>
<CheckBox x:Name="cboxName" Content="Is null ?" Click="cboxName_Click" IsChecked="{Binding Path=THIS, Converter={StaticResource MyContextToBoolConverter}}">
</CheckBox>
</StackPanel>
public class MyContextToBoolConverter: IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return (value!=null);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return parameter;
}
}
I just only want to get DataContext to checkbox from StackPanel.

You should replace THIS with . or completely remove the Path from the Binding. This will create a binding directly to the DataContext.
IsChecked="{Binding Converter={StaticResource MyContextToBoolConverter}}"

Or try this -
<StackPanel x:Name="StackPanel" DataContext="{Binding Path =MyContext}">
<TextBox Text="{Binding Path =Content}" x:Name="tbName" IsReadOnly="False" />
<CheckBox x:Name="cboxName" Content="Is null ?"
Click="cboxName_Click"
IsChecked="{Binding ElementName=StackPanel, Path=DataContext, Converter={StaticResource MyContextToBoolConverter}}">
</CheckBox>
</StackPanel>