All ASP.NET data bound controls have an additional event in ASP.NET 4.5, CreatingModelDataSource. It provides a great way to create our own implementation of ModelDataSource and bind to a control like GridView.
I created a sample ModelDataSource and hooked it up with a GridView in the CreatingModelDataSource event as follows:
protected void gvStudent_CreatingModelDataSource(object sender, CreatingModelDataSourceEventArgs e)
{
e.ModelDataSource = new MyModelDataSource((GridView)sender);
}
Following is the sample ModeldataSource implementation that I wrote:
public class MyModelDataSource : ModelDataSource
{
MyDataSourceView view;
public MyModelDataSource(Control control)
: base(control)
{
}
public override ModelDataSourceView View
{
get
{
if (view == null)
{
view = new MyDataSourceView(this);
}
return view;
}
}
}
And following is MyModelDataSourceView:
public class MyDataSourceView : ModelDataSourceView
{
private MyModelDataSource _owner;
private StudentRepository repository;
public MyDataSourceView(MyModelDataSource owner)
: base(owner)
{
_owner = owner;
repository = new StudentRepository();
}
protected override IEnumerable ExecuteSelect(DataSourceSelectArguments arguments)
{
return repository.GetAll();
}
}
But the ExecuteSelect method doesn't get called automatically. It gets called when I set a SelectMethod to the GridView. As the result of ExecuteSelect method is finally bound to the GridView, specifying the SelectMethod doesn't make any sense here. Also, the event is not fired when gridView.DataBind() is called. Is there any way to kick off the things and make this event called automatically?
CreatingModelDataSource() was put in for the Model data source which is used in Model Binding. When you use model binding you need to specify the Select() method for model binding to work with GridVIew
Related
I've 2 user controls named UCCreateProfile.ascx (used for creating/editing profile data) and UCProfileList.ascx (used to display profile data in GridView). Now whenever a new profile created I want to update my UCProfileList control to show new entry.
The best solution against above problem I've to go for Observer Pattern. In my case UCCreatedProfile is a Subject/Observable and UCProfileList is a Observer and as per pattern definition when observer initialized it knows who is my Subject/Observable and add itself into Subject/Observable list. So whenever a change occurred in Subject/Observable it will be notified.
This pattern best fit my requirements but I'm getting few problems to implement this describe as follows.
I'm working under CMS (Umbraco) and I don't have any physical container page (.aspx). What I've to do is find UCCreateProfile (Subject/Observable) in UCProfileList (Observer) onLoad event using following code.
private Control FindCreateProfileControl()
{
Control control = null;
Control frm = GetFormInstance();
control = GetControlRecursive(frm.Controls);
return control;
}
where GetFormInstance() method is
private Control GetFormInstance()
{
Control ctrl = this.Parent;
while (true)
{
ctrl = ctrl.Parent;
if (ctrl is HtmlForm)
{
break;
}
}
return ctrl;
}
and GetControlRecursive() method is
private Control GetControlRecursive(ControlCollection ctrls)
{
Control result = null;
foreach (Control item in ctrls)
{
if (result != null) break;
if (item is UCCreateProfile)
{
result = item;
return result;
}
if (item.Controls != null)
result = GetControlRecursive(item.Controls);
}
return result;
}
this way I can find the UCCreateProfile (Subject/Observable) user control in UCProfileList (Observer) but the way to find out the (Subject/Observable) is not so fast. As you can see I need to loop through all controls and first find the HtmlForm control and then loop through all child controls under HtmlForm control and find the appropriate control we're looking for.
Secondly, placement of the user controls in container if very important my code will only work if UCCreatedProfile.ascx (Subject/Observable) placed before UCProfileList.ascx (Observer) because this way UCCreateProfile will load first and find in UCProfileList. But if someone changed the position of these 2 controls my code will not work.
So to get rid of these problems I need some solution which works faster and independent of the position of the controls.
I've figured out some solution as described below. Please do let me know if it is a good way of doing this. If there is an alternative, please let me know.
I've a session level variable (a dictionary with Dictionary<ISubject, List<Observer>>) . No matter which user control initialized/loaded first, User Control will add itself into this dictionary.
If Subject/Observable added first, the corresponding observers will be found in this dictionary.
If Observer added first it will added to the dictionary with a null entry. When the Subject added, the association is made.
Regards,
/Rizwan
The Observer pattern is best implemented in .NET via events and delegates. If you use events and delegates, the Dictionary you mention becomes completely unnecessary. See for example this code below (only important pieces shown):
public partial class UserProfile : System.Web.UI.UserControl
{
//This is the event handler for when a user is updated on the UserProfile Control
public event EventHandler<UserUpdatedEventArgs> UserUpdated;
protected void btnUpdate_Click(object sender, EventArgs e)
{
//Do whatever you need above and then see who's subscribed to this event
var userUpdated = UserUpdated;
if (userUpdated != null)
{
//Initialize UserUpdatedEventArgs as you want. You can, for example,
//pass a "User" object if you have one
userUpdated(this,new UserUpdatedEventArgs({....}));
}
}
}
public class UserUpdatedEventArgs : EventArgs
{
public User UserUpdated {get;set;}
public UserUpdatedEventArgs (User u)
{
UserUpdated=u;
}
}
Now subscribing to the UserUpdated event from the UserProfile control on the UserListControl is as easy as this:
public partial class UserList : System.Web.UI.UserControl
{
protected void Page_Load(object sender, EventArgs e)
{
//Find the UserProfile control in the page. It seems that you already have a
//recursive function that finds it. I wouldn't do that but that's for another topic...
UserProfile up = this.Parent.FindControl("UserProfile1") as UserProfile;
if(up!=null)
//Register for the event
up.UserUpdated += new EventHandler<UserUpdatedEventArgs>(up_UserUpdated);
}
//This will be called automatically every time a user is updated on the UserProfile control
protected void up_UserUpdated(object sender, UserUpdatedEventArgs e)
{
User u = e.UserUpdated;
//Do something with u...
}
}
I have a class MyListView, it inherits from ASP.NET ListView. I would like to implement a default behaviour - if a programmer doesn't specify EmptyDataTemplate in aspx code, the MyListView will use a predefined default template (class MyEmptyDataTemplate).
What I have tried is this:
public class MyListView : ListView
{
protected override void CreateChildControls()
{
if (EmptyDataTemplate == null)
EmptyItemTemplate = new MyEmptyDataTemplate();
base.CreateChildControls();
}
}
The MyEmptyDataTemplate implements ITemplate interface. The problem is, that InstantiateIn() method of the MyEmptyDataTemplate is never called, and my default template never appears in case there are no records in datasource. Apparently I wrong understand the ListView component lifecycle and template should be set somewhere else.
Try to do this on the Init event:
public class MyListView : ListView
{
public MyListView()
{
this.Init += (o, e) =>
{
if (EmptyDataTemplate == null)
EmptyDataTemplate = new MyEmptyDataTemplate();
};
}
}
edit
After checking this again I realized that EmptyDataTemplate was checked if emtpy, but the template which has been assigned is EmptyItemTemplate. However both methods are good to instantiate the templates..
Given that every grid, combobox, checkboxlist and in general multi row control supports binding directly to any IEnumerable what is the point of the ObjectDataSource?
Why would one use it as opposed to binding directly to your collection? Particularly if you already have reasonable separation of concerns in your business, presentation and data layers?
I also feel this is an even more relevant question since the introduction of LINQ. I have often found that when binding I would like to perform some further ordering, exclusion and so forth using LINQ and I believe this is not possible when using the ObjectDataSource without creating a specific method for your (potentially single use case)?
So when is it appropriate to use an ObjectDataSource and what are the advantages compared to direct binding to IEnumerable?
First, ObjectDataSource is usually used in ASP.NET WebForms (aspx). ObjectDataSource is located in System.Web.UI.WebControls, as you can see this link on MSDN Library:
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.objectdatasource.aspx
Using ObjectDataSource to bind your data means you bind you'll have datasource as an object, can be in form of DataSet or any other .NET object that implements IEnumerable. Using ObjectDataSource means you have to perform your own Select, Update, Insert and Delete method that usually found in SqlDataSource.
There's this nice walkthrough in MSDN Library: Walkthrough: Data Binding to a Custom Business Object
But binding to a simple IEnumerable without implementing IListSource (like DataTable has) means you won't have nice feature such as data bindings to a complex data control such as GridView. And you'll lose other feature too, because a simple IEnumerable alone can't be bound in two ways to other list control such as ListView and GridView.
To have your data to be bindable two way, your object must also implement INotifyPropertyChanged interface before added into the IListSource as data item.
Samples:
public class Employee : BusinessObjectBase
{
private string _id;
private string _name;
private Decimal parkingId;
public Employee() : this(string.Empty, 0) {}
public Employee(string name) : this(name, 0) {}
public Employee(string name, Decimal parkingId) : base()
{
this._id = System.Guid.NewGuid().ToString();
// Set values
this.Name = name;
this.ParkingID = parkingId;
}
public string ID
{
get { return _id; }
}
const string NAME = "Name";
public string Name
{
get { return _name; }
set
{
if (_name != value)
{
_name = value;
// Raise the PropertyChanged event.
OnPropertyChanged(NAME);
}
}
}
const string PARKING_ID = "Salary";
public Decimal ParkingID
{
get { return parkingId; }
set
{
if (parkingId != value)
{
parkingId = value;
// Raise the PropertyChanged event.
OnPropertyChanged(PARKING_ID);
}
}
}
}
This is the implementation of INotifyPropertyChanged:
public class BusinessObjectBase : INotifyPropertyChanged
{
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
private void OnPropertyChanged(PropertyChangedEventArgs e)
{
if (null != PropertyChanged)
{
PropertyChanged(this, e);
}
}
#endregion
}
You can bind to an enum with it if you dont want codebehind.
The following test:
[TestClass]
public class MyTestClass
{
private TestContext _testContext;
protected TestContext TestContext
{
get { return _testContext; }
set { _testContext = value; }
}
[TestMethod]
[HostType("ASP.NET")]
[UrlToTest("http://localhost/MyPage.aspx")]
public void TestMyPage()
{
TextBox tb = TestContext.RequestedPage.FindControl("ControlId") as TextBox;
Assert.IsNotNull(tb);
}
}
fails, and using the string "ctl00$ContentPlaceHolder1$ControlId" as control Id provide a proper control... I know, ASP.NET contains "ClientID" property for web-controls, but is there any possibility to know in advance the control's client Id in the TEST (Under VS 2008)?
Thanks.
I don't think the ClientID is what you're after here. I think your problem is that FindControl is not doing what you think it is.
FindControl is not recursive. If your textbox is inside of a ContentPlaceHolder, then you need to call FindControl on the placeholder, not the Page.
Otherwise, I suggest writing a recursive FindControl function that will search the entire control heirarchy. You can see an example here.
I need the following functionality in my method: if the method is called before OnLoad event of ASP.NET life cycle throw an exception else continue execution of the method.
I was thinking of something like this:
if (Page.LifeCycleState < LifeCycleState.OnLoad) {
throw new InvalidPageStateException();
}
Is it possible to retrieve the state of ASP.NET page life cycle?
One approach would be to use a Basepage that you always use in your site. This would contain a variable called PageLoadComplete, which you would set at the end of your PageLoad event. Then you could check the state of this variable from within your method.
public abstract class BasePage : System.Web.UI.Page
{
public bool PageLoadComplete { get; private set; }
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
PageLoadComplete = true;
}
}
If you want to access the variable from code external to your page such as a UserControl, you would have to make it public and cast your page as BasePage.
public partial class MyUserControl : System.Web.UI.UserControl
{
protected void Page_Load(object sender, EventArgs e)
{
BasePage basePage = this.Page as BasePage;
if (basePage != null && !basePage.PageLoadComplete)
{
throw new InvalidPageStateException();
}
}
}
There is property in a realization of System.Web.UI.Control class(realization):
internal ControlState ControlState {
get { return _controlState; }
set { _controlState = value; }
}
Where ControlState is enum that contains members such as: Initialized, ViewStateLoaded, Loaded etc. here declaration
But as you can see this property is internal. So only way to get control state is proposed by Daniel Dyson.
You maybe able to find what you are looking for, by looking at the CurrentHandler and PreviousHandler properties of the current HttpContext.
if the method is called before OnLoad event of ASP.NET life cycle
throw an exception else continue execution of the method.
It is not clear which Onload event is meant, nor where the "method" resides. Is it the Page's Onload or a Control's OnLoad? Is it a Page's "method" or a Control's "method"?
Anyway, one can store sort of flag in the Context.Items Dictionary, which all controls (including Page) have access to during a request. This eliminates the need to use a general base page like suggested obove.
In the OnLoad method (no matter whether it is a Page's OnLoad or a Control's OnLoad):
Context.Items[UniqueID] = this;
In the "method":
if (Context.Items[UniqueID] != null)
{
throw new InvalidPageStateException();
}