I have a question regarding binding in WinRT.
I have a Viewmodel like this:
public class MainPageViewModel : INotifyPropertyChanged
{
private ObservableCollection<Vehicle> _vehicles = new ObservableCollection<Vehicle>();
public ObservableCollection<Vehicle> Vehicles
{
get { return _vehicles; }
set { _vehicles = value; }
}
and also I have some properties that I get the value from this main list, for example
public int GetType1Vehicles
{
get { return Vehicles.Where(x => x.Type == Type1).Count(); }
}
public int TotalVehicles
{
get { return Vehicles.Count(); }
}
I binded a UI textbox to a "GetType1Vehicles" and another textbot to a "TotalVehicles". The problem is that when I update the Vehicle List, the ListView with all vehicles is correctly updated but the Total and the Type don't. What I doing wrong?
Anybody can help me? Thanks!
UPDATE
I found a workarround, but I'm not sure that is the best approach. Every time that I change some from the list, call manually the methods:
RaisePropertyChanged("GetType1Vehicles");
RaisePropertyChanged("TotalVehicles");
Is the correct approach?
You are correct in that you will need to manually call RaisePropertyChanged. Anyway, why do you have a TotalVehicles property when you could just bind to "Vehicles.Count"?
David is right, why this TotalVehicles property ?
With an ObservableCollection, you should not call the Count() method, just use the Count property.
The Count method is usefull if you want to count only the items with a specific value, not the size of the collection, that's the job of the property.
Related
I have a base class called BaseEvent and several descendants classes:
public class BaseEvent {
// the some properties
// ...
}
[MapInheritance(MapInheritanceType.ParentTable)]
public class Film : BaseEvent {
// the some properties
// ...
}
[MapInheritance(MapInheritanceType.ParentTable)]
public class Concert : BaseEvent {
// the some properties
// ...
}
I have a code which create the BaseEvent instance at runtime:
BaseEvent event = new BaseEvent();
// assign values for a properties
// ...
baseEvent.XPObjectType = Database.XPObjectTypes.SingleOrDefault(
t => t.TypeName == "MyApp.Module.BO.Events.BaseEvent");
Now, this event will be shows in BaseEvent list view.
I want to do the following: when a user click Edit button then show in list view lookup field with all descendants types. And when user saves record change ObjectType to selected value.
How can I do this?
Thanks.
PS. this is asp.net app.
I'm not sure that your approach is correct for what you are trying to achieve. First, I'll answer the question you have asked, and afterwards I'll try to explain how the XAF already provides the functionality you are trying to achieve, namely how to choose which subclass of record to create from the user interface.
In order to create a property which allows the user to choose a Type within the application, you can declare a TypeConverter:
public class EventClassInfoTypeConverter : LocalizedClassInfoTypeConverter
{
public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context)
{
List<Type> values = new List<Type>();
foreach (ITypeInfo info in XafTypesInfo.Instance.PersistentTypes)
{
if ((info.IsVisible && info.IsPersistent) && (info.Type != null))
{
// select BaseEvent subclasses
if (info.Type.IsSubclassOf(typeof(BaseEvent)))
values.Add(info.Type);
}
}
values.Sort(this);
values.Insert(0, null);
return new TypeConverter.StandardValuesCollection(values);
}
}
And then your base event class would look like:
public class BaseEvent: XPObject
{
public BaseEvent(Session session)
: base(session)
{ }
private Type _EventType;
[TypeConverter(typeof(EventClassInfoTypeConverter))]
public Type EventType
{
get
{
return _EventType;
}
set
{
SetPropertyValue("EventType", ref _EventType, value);
}
}
}
However, I suspect this is not the functionality you require. Modifying the value of the property will NOT change the base type of the record. That is, you will end up with a record of type BaseEvent which has a property Type equal to 'Concert' or 'Film'.
XAF already provides a mechanism for selecting the type of record to create. In your scenario, you will find that the New button is a dropdown with your different subclasses as options:
Therefore you do not need to create a 'type' property within your object. If you need a column to show the type of event in the list view, you can declare a property as follows
[PersistentAlias("XPObjectType.Name")]
public string EventType
{
get
{
return base.ClassInfo.ClassType.Name;
}
}
I am data binding to many FormView controls using EF entity instances, but I have to resort to this ridiculous kludge in order to achieve what I want without using EntityDataSource controls:
propertyHeaderSection.DataSource = new List<PropertyDetailsModel> { _propertyDetails };
I suspect I will have to derive my own control from FormView and enable it to accept an almost POCO as a data source. Where do I start?
This is my implementation, sort of the same idea as patmortech, but i also found out that the ValidateDataSource method on the BaseDataBoundControl is what throws the exception at run-time if your datasource isn't enumerable.
public class CustomFormView : System.Web.UI.WebControls.FormView
{
public override object DataSource
{
get
{
if (!(base.DataSource is IEnumerable))
return new[] {base.DataSource};
return base.DataSource;
}
set
{
base.DataSource = value;
}
}
// This method complains at run time, if the datasource is not
// IListSource, IDataSource or IEnumerbale
protected override void ValidateDataSource(object dataSource)
{
//base.ValidateDataSource(dataSource);
}
}
EDIT:
Considering the suggestion, i've made some changes to the way i check if the assigned DataSource is enumerable or not. I have also managed to create a sample app (VS 2010 Solution) to demo the changes. The app can be downloaded from http://raghurana.com/blog/wp-content/attachments/FormViewDataProblem.zip
In short this is what i am checking to ensure that the existing datasource can be enumerated already or not:
public static bool CanEnumerate( this object obj )
{
if (obj == null) return false;
Type t = obj.GetType();
return t.IsArray ||
t.Implements(typeof (IEnumerable).FullName) ||
t.Implements(typeof (IListSource).FullName) ||
t.Implements(typeof (IDataSource).FullName);
}
Please feel free to suggest more changes, if this isnt quite the desired functionality. Cheers.
Not sure it's the best idea in the world, but this is how you could derive from FormView to allow single object data source values. It basically does the same check that the ValidateDataSource does internally, and then creates a list wrapper for the item if it's not already a valid type.
public class SingleObjectFormView : System.Web.UI.WebControls.FormView
{
public override object DataSource
{
get
{
return base.DataSource;
}
set
{
//will check if it's an expected list type, and if not,
//will put it into a list
if (! (value == null || value is System.Collections.IEnumerable || value is System.ComponentModel.IListSource || value is System.Web.UI.IDataSource) )
{
value = new List<object> { value };
}
base.DataSource = value;
}
}
}
When using N2 CMS:
If I want to set some default values when a new ContentItem is created (e.g. setting the CreatedByUser value for a new Page so I can record who originally created it) where is the best place to put that code?
I figure the constructor of the ContentItem isn't ideal because that will get called when existing objects are loaded.
If you're using the Get/SetDetail syntax then you can do something like this in the property getter:
public virtual string TopImage
{
get { return (string)(GetDetail("TopImage") ?? string.Empty); }
set { SetDetail("TopImage", value); }
}
That's a bit ugly, so there's also an overload for Get/Set detail that lets you specify the default:
public virtual string TopImage
{
get { return GetDetail("TopImage", String.Empty /* Default */); }
set { SetDetail("TopImage", value, String.Empty /* Default */); }
}
If you want to save a value when something is saved then try overriding the AddTo method on the ContentItem. This is called every time the object is saved, so be careful if you only want to call it the first time something is saved (ID == 0 when an Item is "new")
I have an Asp.Net GridView. One of the Columns is a List, but I only want to show the Last Item in the list. How can I do this?
List<string> Column1
I am binding the Gridview to a business object:
public Class GridObject
{
List<string> Column1 { get; set; }
}
EDIT
This worked, but is it the best solution:
<%# ((List<string>)Eval("Column1"))[((List<string>)Eval("Column1")).Count - 1] %>
I would add a property to the object you are binding to, and use that property instead of the list property in your binding.
public Class GridObject
{
List<string> Column1 { get; set; }
public string Column1LastValue
{
get
{ // return Column1.Last(); if linq is available
return Column1[Column1.Count-1];
}
}
}
Edit: Adding a presentation wrapper allows you to unit test what will be displayed. You are doing a translation in the view, which is OK, but since you technically have some logic happening to translate your business object to something proper for display, you would likely want to unit test that translation. Then, any formatting you want to apply to any of your business object fields is wrapped in a testable class, rather than hidden on the untestable view. Here is a sample of how this could be done:
public class GridObjectView
{
private GridObject _gridObject;
public GridObjectView(GridObject gridObject)
{
_gridObject = gridObject;
}
public string Column1
{
get
{
return _gridObject.Column1.Last();
}
}
}
Then to do the databinding, you could do this:
List<GridObject> data = GetGridData();
grid.DataSource = data.Select(g => new GridObjectView(g));
grid.DataBind();
Your best bet is to create a template column and use an inline script to retrieve the value from the list:
<%= ((List<string>)DataBinder.Eval("Column1"))[((List<string>)DataBinder.Eval("Column1")).Count] %>
Or you could store the result in the text of a label or a literal.
Hope that helps
In Flex I'm using the following code to allow sorting in a DataGrid (the data is paged and sorted serverside).
private function headerReleaseHandler(event:DataGridEvent):void
{
var column:DataGridColumn = DataGridColumn(event.currentTarget.columns[event.columnIndex]);
if(this.count>0)
{
if(this.query.SortField == column.dataField)
{
this.query.SortAscending = !this.query.SortAscending;
}
else
{
this.query.SortField = column.dataField;
this.query.SortAscending = true;
}
this.fill();
}
event.preventDefault();
}
This works perfectly, except that the arrows that indicate sorting isn't shown. How can I accomplish that?
Thanks!
/Niels
There is an example here if this is what you are looking for:
http://blog.flexexamples.com/2008/02/28/displaying-the-sort-arrow-in-a-flex-datagrid-control-without-having-to-click-a-column/
It looks like you need to refresh the collection used by your dataprovider.
I have encountered the same problem and the only solution I found was to override the DataGrid and create a custom one.
Here is the class:
public class DataGridCustomSort extends DataGrid
{
public function DataGridCustomSort()
{
super();
addEventListener(DataGridEvent.HEADER_RELEASE,
headerReleaseHandlerCustomSort,
false, EventPriority.DEFAULT_HANDLER);
}
public function headerReleaseHandlerCustomSort(event:DataGridEvent):void {
mx_internal::sortIndex = event.columnIndex;
if (mx_internal::sortDirection == null || mx_internal::sortDirection == "DESC")
mx_internal::sortDirection = "ASC";
else
mx_internal::sortDirection = "DESC";
placeSortArrow();
}
}
You have to specifically call the placeSortArrow() method when you get the HEADER_RELEASE event and set the column index and direction information.
in the above code what does "this" refer to is it the datagrid because I am confused by this.query.SortField , I am assuming 'this' and "query' are your own custom objects. and why are you checking for count. what count is that.
Regards
-Mohan