The data binding isn't working, what have I done wrong?

Question

I'm writing a very simple WPF app, one view. I've got a few models defined for the small handful of tables this app works with. I'm making some sort of boneheaded mistake, but I can't see what it is. I'm trying to bind to a property of one of the model
classes I've define, to a textbox in a stackpanel. Here's the XAML:
<StackPanel Orientation="Horizontal" Margin="0, 5" DataContext="{Binding cvsSpecMapping}">
<TextBlock Margin="10,0,5,0">Specimen Mapping: </TextBlock>
<TextBox x:Name="txtHl7SpecMap"
Text="{Binding HL7SpecimenTypeName}"
ToolTip="{Binding HL7SpecimenTypeName}"
MinWidth="50"
MaxWidth="100"
MaxLength="250" />
</StackPanel>
Earlier in the same XAML file I've got the following collection view source defined in the windows' resources:
<CollectionViewSource x:Key="cvsSpecMapping" />
This isn't rocket science. Here's the model class definition. I'm removing all but the relevant property:
using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;
namespace SpecMapException.Models
* This class I am interested in knowing what properties change.
* Also note that the properties in this class do NOT represent all of the properties
* in the Prism.SpecimenMapping table. It only represents what this application has
* to store.
public class SpecimenMapping : INotifyPropertyChanged
private const int MAX_HL7SPECIMENTYPENAME_LEN = 250;
#region class properties
private string _hl7SpecimenTypeName = "";
public string HL7SpecimenTypeName
get { return _hl7SpecimenTypeName; }
set
if (value != _hl7SpecimenTypeName)
_hl7SpecimenTypeName = EnforceMaxLength(value, MAX_HL7SPECIMENTYPENAME_LEN);
NotifyPropertyChanged();
#endregion //class properties
#region local routines
private string EnforceMaxLength(string PassedValue, int MaxLength)
if (PassedValue.Length <= MaxLength)
return PassedValue;
return PassedValue.Substring(0, MaxLength);
#endregion
#region PropertyChanged code
* The usual property changed code.
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
#endregion
And lastly here's the relevant code which I've put into the windows Loaded event:
Models.SpecimenMapping sm = null;
private void Window_Loaded(object sender, RoutedEventArgs e)
var cvsSpecMapNames = (CollectionViewSource)(this.FindResource("cvsSpecMapping"));
cvsSpecMapNames.Source = sm;
So what is the mistake that I've made? Why isn't the data binding to the textbox txtHl7SpecMap working?
(I'm using VS 2013, .NET 4.5.)
Rod

Answer 1

cvsSpecMapping is a resource and not a property so you should set the DataContext using the StaticResource markup extension instead of Binding:
<StackPanel Orientation="Horizontal" Margin="0, 5" DataContext="{StaticResource cvsSpecMapping}">
Also, the Source property of a CollectionViewSource is supposed to be set to a collection:
private void Window_Loaded(object sender, RoutedEventArgs e)
sm = new Models.SpecimenMapping();
var cvsSpecMapNames = (CollectionViewSource)(this.FindResource("cvsSpecMapping"));
cvsSpecMapNames.Source = new List<Models.SpecimenMapping>() { sm };
You may also want to set a default value of the HL7SpecimenTypeName property to confirm that the binding actually works after you have done the above changes:
public class SpecimenMapping : INotifyPropertyChanged
private const int MAX_HL7SPECIMENTYPENAME_LEN = 250;
#region class properties
private string _hl7SpecimenTypeName = "def....";
public string HL7SpecimenTypeName
get { return _hl7SpecimenTypeName; }
set
if (value != _hl7SpecimenTypeName)
_hl7SpecimenTypeName = EnforceMaxLength(value, MAX_HL7SPECIMENTYPENAME_LEN);
NotifyPropertyChanged();
Hope that helps.
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