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Show ToString of a Collection Wrapper Class in DataGridView

I have a class that has one of its properties being of type ObservableCollection<string>
public class SizeList
{
public string ID { get; set; }
public string Name { get; set; }
//public ObservableCollection<string> List { get; set; }
public ListEntryCollection List { get; set; }
}
During a unit test I return a list of SizeList and then show it in a DataGridView to check the results I am expecting, the data is fine but I am missing the field List in the DGV; only the ID and Name are shown, so I have made a wrapper class for the ObservableCollection<string> and overriden its .ToString() method:
namespace System.Collections.ObjectModel
{
using System.Collections.Generic;
public class ListEntryCollection : ObservableCollection<string>
{
public ListEntryCollection(IEnumerable<string> collection)
: base(collection)
{
}
public override string ToString()
{
return Count.ToString() + ((Count > 1) ? " Entries": " Entry");
}
}
}
But I am still not getting the List field in the DGV, so what am I doing wrong ?

Per Column Types in the Windows Forms DataGridView Control, the only property types for which bound columns are automatically generated are numbers, text, booleans, and images.
To display other types, you need to add the column manually to the DataGridView, or use a custom column type (and even then, you'll probably have to add it manually.)
A couple of options present themselves:
You could try adding a read-only property to SizeList to display the description of the list, and see if that will result in a column being automatically created.
You can try adding a column manually, which I believe you can do in the Form Designer if you click on the DataGridView. You will probably have to override a method or two, or use an event handler, in order to change the display from the default. (It's possible, though, that it will use the ToString override you created, in which case the problem is solved.)
Or, you could create a ListSummaryDataGridViewColumn class, that can represent a list by display a count of the items in it, and add one of those manually.

ObservableCollection not showing up in UI

I'm trying to display list of items in XAML. I get the list from public API, convert it to the class I need and then I want to display it.
public static async Task PopulateListAsync(ObservableCollection<MyClass> myList) {
var listContainer = await GetListAsync();
foreach (var item in listContainer) {
//converting from one class to another, editing some properties and such
myList.Add(item );
}
}
and on the MainPage.cs I had
public ObservableCollection<MyClass> Value { get; set; }
public MainPage() {
this.InitializeComponent();
Value = new ObservableCollection<MyClass>();
}
private async void Page_Loaded(object sender, RoutedEventArgs e) {
await PopulateListAsync(Value);
}
And I displayed in the XAML fine.
But then I wanted to introduce filtering. So I get the data, convert them to some class and insert them to a list, which I then filter with LINQ (seems easier then filtering in ObservableCollection).
Basically I replaced the PopulateListAsync() with FormatListAsync() which instead of inserting the data directly into the ObservableCollection<>, returns a List<>. Then I have a "middle man" function
public static async Task PopulateListAsync(ObservableCollection<MyClass> myList) {
myList = new ObservableCollection<MyClass>(await FormatListAsync());
//filtering itself isn't implemented yet, but it would be placed here
}
I probably could just loop trough mylist and add it one by one into the ObservableCollection<>, but I feel like there surely is a better way.
I think I'm supposed to implement some PropertyChanged event or something like that, but I tried a few (this one for example), unsuccessfully. I don't think I quite understand how to implement it.

If you are assign new value for method parameter then you just change reference's copy to the collection and don't change source reference. You can read more about passing reference types as method parameters on MSDN.
Also, if you will change property that not implements INotifyPropertyChanged itself then you'll have no changes in UI because your view doesn't know about the changes.
In the simple and easy way you can manipulate source collection instead of creating new one. Just do something like
public static async Task PopulateListAsync(ObservableCollection<MyClass> myList)
{
// newList can be an List<MyClass> type, not ObservableCollection
var newList = await FormatListAsync();
// change displayed list with new data
myList.Clear();
foreach(var newValue in newList)
myList.Add(newValue);
}
The other option, you can implement INotifyPropertyChanged for your ViewModel and raise PropertyChanged event in the setter of Value property:
private ObservableCollection<MyClass> _value;
public ObservableCollection<MyClass> Value
{
get
{
return _value;
}
set
{
// I hope this line of code will convince you to give more clear variable name
if(value != _value)
{
_value = value;
NotifyPropertyChanged(nameof(Value));
}
}
}
Also, you'll need to assign Value directly in the PopulateListAsync():
public static async Task PopulateListAsync()
{
Value = new ObservableCollection<MyClass>(await FormatListAsync());
}

Binding to property of a class derived from CollectionBase

I am trying to bind some controls to an object - which is normally a pretty straightforward process. Unfortunately, if the object that I'm binding to inherits from CollectionBase, binding to that classes fields causes the error:
Cannot bind to the property or column Caption on the DataSource. Parameter name: dataMember
Removing the collectionbase inheiritance makes this issue go away, but I need this object to be a collection. It seems as though CollectionBase causes higher level properties to become "unbindable." Is there some property I can override to fix this? Any other ideas?
I found this example online that summarized the issue pretty easily. Unfortunately, I have yet to find an answer in all the places I've seen this example posted.
Code:
[STAThread]
static void Main()
{
TestCollection obj = new TestCollection();
using (Form f = new Form())
using (BindingSource bs = new BindingSource())
{
bs.DataSource = typeof(Test);
f.DataBindings.Add("Text", bs, "Caption");
bs.DataSource = obj; // breaks
//List<TestallData = new List<Test>();
//allData.Add(obj);
//bs.DataSource = allData;
f.ShowDialog();
}
}
class TestCollection : CollectionBase
{
public string Caption { get { return "Working"; } }
}

CollectionBase provides interfaces for a List of Objects, as such when used as a datasource the binding tries to look inside the list for the individual binding data. When there is no list, you have a problem.
If you want a the caption and you want to use CollectionBase you should have 2 classes involved, not just one.
public class TestObj
{
public string caption { get { return "yay"; } }
}
public class TestCol : CollectionBase
{
//methods that implement CollectionBase for the TestObj type
}
with those two you can bind one of two ways.
TestObj obj = new TestObj();
TestCol col = new TestCol();
col.Add(obj);
//bind to obj, OR bind to col. Both would work with this setup.
http://msdn.microsoft.com/en-us/library/system.collections.collectionbase%28v=vs.90%29.aspx
There is a sample implementation of CollectionBase there.
UPDATE: EDITED FROM COMMENT
There isn't any method that I personally know which allows you to bind to the outer properties of a collection. As a workaround, you can use a 3 class system (yea, I know, more and more complicated).
public class TestHeader
{
public string Data {get;set;}
}
public class TestCol : CollectionBase
{
//...
}
public class TestObj
{
public TestHeader header {get;set;}
public TestCol col {get;set;}
}
bind the outer fields to TestObj.header and bind the collection fields to TestObj.col. This is a workaround, but as stated I dont actually know a way to directly implement what you seem to want. I wish I did, There are portions of my own code that would benefit from it.
Another Example
You could also do it with two classes, but you would still need to nest the collection itself
public class TestObj
{
public string data {get;set;}
public TestCol col {get;set;}
}
In this case, bind single data fields to TestObj, and collection fields to TestObj.col

How to Bind Listbox in WPF to a generic list?

i'm having trouble getting a clear answer for this.
I have a Static class (DataHolder) that holds a static list with a complex type (CustomerName and CustomerID properties).
I want to bind it to a ListBox in WPF but add another item that will have the word "All" for future drag and drop capablilities.
Anyone?

Create a ViewModel Class you can databind to! The ViewModel can reference the static class and copy the items to its own collection and add the all item to it.
Like this
public class YourViewModel
{
public virtual ObservableCollection<YourComplexType> YourCollection
{
get
{
var list = new ObservableCollection<YourComplexType>(YourStaticClass.YourList);
var allEntity = new YourComplexType();
allEntity.Name = "all";
allEntity.Id = 0;
list.Insert(0, allEntity);
return list;
}
}
}
Note, sometimes, you need empty Items. Since WPF can't databind to null values you need to use the same approach to handle it. The empty business entity has been a best practice for it. Just google it.

That "All" item has to be part of the list you bind your ListBox against. Natuarally you can not add that item to the DataHolder list because it holds items of type Customer (or similar). You could of course add a "magic" Customer that always acts as the "All" item but that is for obvious reasons a serious case of design smell (it is a list of Customers after all).
What you could do, is to not bind against the DataHolder list directly but introduce a wrapper. This wrapper would be your ViewModel. You would bind your ListBox agains a list of CustomerListItemViewModel that represents either a Customer or the "All" item.
CustomerViewModel
{
string Id { get; private set; }
string Name { get; set; }
public static readonly CustomerViewModel All { get; private set; }
static CustomerViewModel()
{
// set up the one and only "All" item
All = new CustomerViewModel();
All.Name = ResourceStrings.All;
}
private CustomerViewModel()
{
}
public CustomerViewModel(Customer actualCustomer)
{
this.Name = actualCustomer.Name;
this.Id = actualCustomer.Id;
}
}
someOtherViewModel.Customers = new ObservableCollection<CustomerViewModel>();
// add all the wrapping CustomerViewModel instances to the collection
someOtherViewModel.Customers.Add(CustomerViewModel.All);
And then in your Drag&Drop code somewhere in the ViewModel:
if(tragetCustomerViewModelItem = CustomerViewModel.All)
{
// something was dropped to the "All" item
}
I might have just introduced you to the benefits of MVVM in WPF. It saves you a lot of hassle in the long run.

If you use binding than the data provided as the source has to hold all of the items, ie. you can't databind and then add another item to the list.
You should add the "All" item to the DataHolder collection, and handle the 'All' item separately in your code.

Visual Studio Design Time Property - Form List Drop Down

[EDIT] To be clear, I know how to get a list of forms via reflection. I'm more concerned with the design time property grid.
I have a user control with a public property of the type Form.
I want to be able to select a form at design time from a dropdown.
I want to populate the form dropdown list from a set namespace: UI.Foo.Forms
This would work like if you have a public property of Control. At design time, the property will automatically populate a dropdown with all the controls on the form, for you to select from. I just want to populate it with all the forms in a namespace.
How do I go about doing this? I hope I'm being clear enough so there is no confusion. I'm looking for some code examples if at all possible. I'm trying to avoid having to spend too much time on this when I have other deadlines to meet.
Thanks for your help in advance.

You can easily get the classes via Reflection:
var formNames = this.GetType().Assembly.GetTypes().Where(x => x.Namespace == "UI.Foo.Forms").Select(x => x.Name);
Assuming you're calling this from code in the same assembly as your forms, you'll get the names of all the types that are in the "UI.Foo.Forms" namespace. You can then present this in the dropdown and, eventually, instantiate whichever is selected by the user via reflection once more:
Activator.CreateInstance(this.GetType("UI.Form.Forms.FormClassName"));
[Edit] Adding code for the design time stuff:
On your control you can create a Form property as such:
[Browsable(true)]
[Editor(typeof(TestDesignProperty), typeof(UITypeEditor))]
[DefaultValue(null)]
public Type FormType { get; set; }
Which references the Editor type that must be defined. The code is pretty self-explanatory, with a minimal amount of tweaking, you'll likely be able to get it to produce exactly what you want.
public class TestDesignProperty : UITypeEditor
{
public override UITypeEditorEditStyle GetEditStyle(ITypeDescriptorContext context)
{
return UITypeEditorEditStyle.DropDown;
}
public override object EditValue(ITypeDescriptorContext context, IServiceProvider provider, object value)
{
var edSvc = (IWindowsFormsEditorService)provider.GetService(typeof(IWindowsFormsEditorService));
ListBox lb = new ListBox();
foreach(var type in this.GetType().Assembly.GetTypes())
{
lb.Items.Add(type);
}
if (value != null)
{
lb.SelectedItem = value;
}
edSvc.DropDownControl(lb);
value = (Type)lb.SelectedItem;
return value;
}
}

The dropdown does not close when item gets selected by clicking it, so this could be useful:
assign the click event handler for the listbox and add the event handler function
public class TestDesignProperty : UITypeEditor
{
// ...
IWindowsFormsEditorService editorService;
public override object EditValue(ITypeDescriptorContext context, IServiceProvider provider, object value)
{
// ...
editorService = edSvc ; // so can be referenced in the click event handler
ListBox lb = new ListBox();
lb.Click += new EventHandler(lb_Click);
// ...
}
void lb_Click(object sender, EventArgs e)
{
editorService.CloseDropDown();
}
}