xaml Convert ID to String without using ComboBox - wpf

Question

I've been using code like this
<ComboBox ItemsSource="{Binding Path=CompaniesViewModel.CompaniesCollection}"
SelectedValuePath="CompanyId"
SelectedValue="{Binding Path=CompanyId}"
IsEnabled="False"
DisplayMemberPath="CompanyName"
/>
To display a Company Name in a ComboBox. Notice how the IsEnabled is set to false...that's because I really don't want the user to use the ComboBox. I am just using it as an easy way to convert an ID to string for display purposes.
When I put items in a Grid and there are a lot of them, I think it is really hurting the rendering performance. When I remove the ComboBox it loads in a split second. When the ComboBox is used in the code it can take 20 seconds.
I guess my question is I think I should be using a Label or TextBlock but not sure how to get the binding to work correctly as They don't have an ItemsSource or a SelectedValuePath or SelectedValue.
I thought about writing an IValueConverter but not sure how to bind/pass in the 3 values. I'd have to pass in the collection, the ValuePath and the Value ID.
Any thoughts or suggestions?

Answer 1

Put a
public Company Company {get {return CompaniesCollection.FirstOrDefault(x => x.CompanyId == CompanyId); }}
property in the ViewModel.

Answer 2

I welcome any of you to examine my code to see if you can make it more efficient but this is what I ended up doing.
<cc:LookupLabel
ItemsSource="{Binding Path=CompaniesCollection}"
SelectedValuePath="CompanyId"
SelectedValue="{Binding Path=CompanyId}"
DisplayMemberPath="CompanyName"
/>
And below is the LookupLabel derived from Label and INotifyPropertyChanged. I'm not sure how Microsoft implements this efficiently but this was my best stab at it. In particular the GetContent method listed at the bottom. All the other stuff is just the messy DependencyProperty declarations.
using System;
using System.Collections;
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
namespace CustomControls
{
public class LookupLabel : Label, INotifyPropertyChanged
{
public LookupLabel()
{
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
#region ItemsSource
public static readonly DependencyProperty ItemsSourceProperty =
DependencyProperty.Register("ItemsSource", typeof(IEnumerable), typeof(LookupLabel)
, new UIPropertyMetadata(null, LookupLabel.ItemsSourceChanged)
);
private static void ItemsSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
LookupLabel t = d as LookupLabel;
t.NotifyPropertyChanged("ItemsSource");
t.Content = GetContent(t);
}
[Bindable(true)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public IEnumerable ItemsSource
{
get
{
return (IEnumerable)GetValue(ItemsSourceProperty);
}
set
{
SetValue(ItemsSourceProperty, value);
}
}
#endregion ItemsSource
#region SelectedValue
public static readonly DependencyProperty SelectedValueProperty =
DependencyProperty.Register("SelectedValue", typeof(object), typeof(LookupLabel)
, new UIPropertyMetadata(null, LookupLabel.SelectedValueChanged)
);
private static void SelectedValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
LookupLabel t = d as LookupLabel;
t.NotifyPropertyChanged("SelectedValue");
t.Content = GetContent(t);
}
[Localizability(LocalizationCategory.NeverLocalize)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
[Bindable(true)]
[Category("Appearance")]
public object SelectedValue
{
get
{
return (object)GetValue(SelectedValueProperty);
}
set
{
SetValue(SelectedValueProperty, value);
}
}
#endregion SelectedValue
#region SelectedValuePath
public static readonly DependencyProperty SelectedValuePathProperty =
DependencyProperty.Register("SelectedValuePath", typeof(string), typeof(LookupLabel)
, new UIPropertyMetadata(string.Empty, LookupLabel.SelectedValuePathChanged)
);
private static void SelectedValuePathChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
LookupLabel t = d as LookupLabel;
t.NotifyPropertyChanged("SelectedValuePath");
t.Content = GetContent(t);
}
[Localizability(LocalizationCategory.NeverLocalize)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
[Bindable(true)]
[Category("Appearance")]
public string SelectedValuePath
{
get
{
return (string)GetValue(SelectedValuePathProperty);
}
set
{
SetValue(SelectedValuePathProperty, value);
}
}
#endregion SelectedValuePath
#region DisplayMemberPath
public static readonly DependencyProperty DisplayMemberPathProperty =
DependencyProperty.Register("DisplayMemberPath", typeof(string), typeof(LookupLabel)
, new UIPropertyMetadata(string.Empty, LookupLabel.DisplayMemberPathChanged)
);
private static void DisplayMemberPathChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
LookupLabel t = d as LookupLabel;
t.NotifyPropertyChanged("DisplayMemberPath");
t.Content = GetContent(t);
}
[Localizability(LocalizationCategory.NeverLocalize)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
[Bindable(true)]
[Category("Appearance")]
public string DisplayMemberPath
{
get
{
return (string)GetValue(DisplayMemberPathProperty);
}
set
{
SetValue(DisplayMemberPathProperty, value);
}
}
#endregion DisplayMemberPath
protected static object GetContent(LookupLabel label)
{
if (label.ItemsSource == null)
{
return null;
}
if (string.IsNullOrWhiteSpace(label.SelectedValuePath))
{
return null;
}
if (string.IsNullOrWhiteSpace(label.DisplayMemberPath))
{
return null;
}
if (label.SelectedValue == null)
{
return null;
}
object result = null;
System.Reflection.PropertyInfo valuePropertyInfo = null;
foreach (var item in label.ItemsSource)
{
if (valuePropertyInfo == null)
{
valuePropertyInfo = item.GetType().GetProperty(label.SelectedValuePath);
if (valuePropertyInfo == null)
{
return null;
}
}
if (valuePropertyInfo.GetValue(item, null).Equals(label.SelectedValue))
{
var displayPropertInfo = item.GetType().GetProperty(label.DisplayMemberPath);
if (displayPropertInfo == null)
{
return null;
}
else
{
result = displayPropertInfo.GetValue(item, null);
break;
}
}
}
return result;
}
}
}

Answer 3

I am guessing that your combobox is taking too long to load because your collection has a lot of items.
You shouldn't be loading all your companies if you'll just show one of them, as a general good-practice.
I don't quite grasp your intent in using the combobox. Is it the style? can it be enabled in the future?
If it is only an easy way of displaying the CompanyName then i'd suggest the following:
Bind directly to CompanyName property.
-OR-
in the code-behind, create a calculated property named "CompanyDisplayName" that gets your company name.
Bind to it in the XAML
in the code-behind, whenever the current selected Company instance or the CompanyId changes fire 'OnPropertyChanged("CompanyDisplayName")
Try a TextBlock or a readonly TextBox to enable copy/paste;
For more info on the NotifyPropertyCahnged paradigm read here