问题
I want to take an object, let's say this object:
public class BenchmarkList
{
public string ListName { get; set; }
public IList<Benchmark> Benchmarks { get; set; }
}
and have that object display its ListName as the "name" part of the PropertiesGrid ("Benchmark" would be good), and for the "value" part of the PropertyGrid, to have a drop-down list of the IList<> of Benchmarks:
here is the Benchmark object
public class Benchmark
{
public int ID {get; set;}
public string Name { get; set; }
public Type Type { get; set; }
}
I would want the drop-down to show the Name property of the Benchmark for what the users can see. Here is a visual example:
So, essentially, I'm trying to get a collection of Benchmark objects into a drop-down list, and those objects should show their Name property as the value in the drop-down.
I've read other articles on using the PropertiesGrid, including THIS and THIS, but they are more complex than what I'm trying to do.
I usually work on server-side stuff, and don't deal with UI via WebForms or WinForms, so this PropertiesGrid is really taking me for a ride...
I do know my solution lies in implementing "ICustomTypeDescriptor", which will allow me to tell the PropertiesGrid what values it should be displaying regardless of the properties of the object to which I want to bind into the drop-down list, but I'm just not sure how or where to implement it.
Any pointers/help would be much appreciated.
Thanks, Mike
UPDATE:
Okay, so I'm changing the details around a little. I was going overboard before with the objects I thought should be involved, so here is my new approach.
I have an object called Analytic. This is the object that should be bound to the PropertiesGrid. Now, if I expose a property that is of an enum type, PropertiesGrid will take care of the drop-down list for me, which is very nice of it. If I expose a property that is a collection of a custom type, PropertiesGrid is not so nice...
Here is the code for Analytic, the object I want to bind to the PropertiesGrid:
public class Analytic
{
public enum Period { Daily, Monthly, Quarterly, Yearly };
public Analytic()
{
this.Benchmark = new List<IBenchmark>();
}
public List<IBenchmark> Benchmark { get; set; }
public Period Periods { get; set; }
public void AddBenchmark(IBenchmark benchmark)
{
if (!this.Benchmark.Contains(benchmark))
{
this.Benchmark.Add(benchmark);
}
}
}
Here is a short example of two objects that implement the IBenchmark interface:
public class Vehicle : IBenchmark
{
public Vehicle()
{
this.ID = "00000000-0000-0000-0000-000000000000";
this.Type = this.GetType();
this.Name = "Vehicle Name";
}
public string ID {get;set;}
public Type Type {get;set;}
public string Name {get;set;}
}
public class PrimaryBenchmark : IBenchmark
{
public PrimaryBenchmark()
{
this.ID = "PrimaryBenchmark";
this.Type = this.GetType();
this.Name = "Primary Benchmark";
}
public string ID {get;set;}
public Type Type {get;set;}
public string Name {get;set;}
}
These two objects will be added to the Analytic object's Benchmark List collection in the WinForms code:
private void Form1_Load(object sender, EventArgs e)
{
Analytic analytic = new Analytic();
analytic.AddBenchmark(new PrimaryBenchmark());
analytic.AddBenchmark(new Vehicle());
propertyGrid1.SelectedObject = analytic;
}
Here is a screen-grab of the output in the PropertiesGrid. Note that the property exposed as an enum gets a nice drop-down list with no work, but the property exposed as an of List on gets a value of (Collection). When you click on (Collection), you get the Collection editor and then can see each object, and their respective properties:
This is not what I'm looking for. Like in my first screen grab in this post, I'm trying to render the property Benchmark collection of List as a drop-down list that shows the object's name property as the text of what can be displayed...
Thanks
回答1:
In general, a drop down list in a property grid is used for setting the value of a property, from a given list. Here that means you should better have a property like "Benchmark" of type IBenchmark and a possible list of IBenchmark somewhere else. I have taken the liberty of changing your Analytic class like this:
public class Analytic
{
public enum Period { Daily, Monthly, Quarterly, Yearly };
public Analytic()
{
this.Benchmarks = new List<IBenchmark>();
}
// define a custom UI type editor so we can display our list of benchmark
[Editor(typeof(BenchmarkTypeEditor), typeof(UITypeEditor))]
public IBenchmark Benchmark { get; set; }
[Browsable(false)] // don't show in the property grid
public List<IBenchmark> Benchmarks { get; private set; }
public Period Periods { get; set; }
public void AddBenchmark(IBenchmark benchmark)
{
if (!this.Benchmarks.Contains(benchmark))
{
this.Benchmarks.Add(benchmark);
}
}
}
What you need now is not an ICustomTypeDescriptor, but instead a TypeConverter an an UITypeEditor. You need to decorate the Benchmark property with the UITypeEditor (as above) and the IBenchmark interface with the TypeConverter like this:
// use a custom type converter.
// it can be set on an interface so we don't have to redefine it for all deriving classes
[TypeConverter(typeof(BenchmarkTypeConverter))]
public interface IBenchmark
{
string ID { get; set; }
Type Type { get; set; }
string Name { get; set; }
}
Here is a sample TypeConverter implementation:
// this defines a custom type converter to convert from an IBenchmark to a string
// used by the property grid to display item when non edited
public class BenchmarkTypeConverter : TypeConverter
{
public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
{
// we only know how to convert from to a string
return typeof(string) == destinationType;
}
public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
{
if (typeof(string) == destinationType)
{
// just use the benchmark name
IBenchmark benchmark = value as IBenchmark;
if (benchmark != null)
return benchmark.Name;
}
return "(none)";
}
}
And here is a sample UITypeEditor implementation:
// this defines a custom UI type editor to display a list of possible benchmarks
// used by the property grid to display item in edit mode
public class BenchmarkTypeEditor : UITypeEditor
{
private IWindowsFormsEditorService _editorService;
public override UITypeEditorEditStyle GetEditStyle(ITypeDescriptorContext context)
{
// drop down mode (we'll host a listbox in the drop down)
return UITypeEditorEditStyle.DropDown;
}
public override object EditValue(ITypeDescriptorContext context, IServiceProvider provider, object value)
{
_editorService = (IWindowsFormsEditorService)provider.GetService(typeof(IWindowsFormsEditorService));
// use a list box
ListBox lb = new ListBox();
lb.SelectionMode = SelectionMode.One;
lb.SelectedValueChanged += OnListBoxSelectedValueChanged;
// use the IBenchmark.Name property for list box display
lb.DisplayMember = "Name";
// get the analytic object from context
// this is how we get the list of possible benchmarks
Analytic analytic = (Analytic)context.Instance;
foreach (IBenchmark benchmark in analytic.Benchmarks)
{
// we store benchmarks objects directly in the listbox
int index = lb.Items.Add(benchmark);
if (benchmark.Equals(value))
{
lb.SelectedIndex = index;
}
}
// show this model stuff
_editorService.DropDownControl(lb);
if (lb.SelectedItem == null) // no selection, return the passed-in value as is
return value;
return lb.SelectedItem;
}
private void OnListBoxSelectedValueChanged(object sender, EventArgs e)
{
// close the drop down as soon as something is clicked
_editorService.CloseDropDown();
}
}
来源：https://stackoverflow.com/questions/5171037/display-list-of-custom-objects-as-a-drop-down-in-the-propertiesgrid