When I am not using data controls like the DataForm and DataGrid is there any use for the attributes like [Required], [StringLength] on my entities? Can these be used for validation outside of the above mentioned data controls?
If so, could you point me to some examples or documentation. I would like to prevent users from pressing the OK button if there are any validation errors and would like to avoid the throwing of exceptions from the setters(possible?).
Yes, those can be used for validation without using UI controls. Brad Abrams has a blog post with details on using those attributes for data forms, but seems like you should be able to separate the UI portion of his post from the core validation logic.
From the post, here's a sample property with validation logic added manually.
[DataMember()]
[Key()]
[ReadOnly(true)]
public int EmployeeID
{
get
{
return this._employeeID;
}
set
{
if ((this._employeeID != value))
{
ValidationContext context = new ValidationContext(
this, null, null);
context.MemberName = "EmployeeID";
Validator.ValidateProperty(value, context);
this._employeeID = value;
this.OnPropertyChanged("EmployeeID");
}
}
}
Related
In page edit mode I want to show a read-only text that is based on a page property value. The text could for example be "A content review reminder email will be sent 2015-10-10", where the date is based on the page published date + six months (a value that will be configurable and therefore can change anytime). So far I've tried to accomplish something like this by adding another property on the page.
I've added the property CurrentReviewReminderDate to an InformationPage class we use. In page edit mode the property name is shown, but it doesn't have a value. How do I do to show the value in page edit mode (preferably as a label)?
[CultureSpecific]
[Display(
Name = "Review reminder date",
Description = "On this date a reminder will be sent to the selected mail to remember to verify page content",
Order = 110)]
[Editable(false)]
public virtual string CurrentReviewReminderDate
{
get
{
var daysUntilFirstLevelReminder =
int.Parse(WebConfigurationManager.AppSettings["PageReviewReminder_DaysUntilFirstLevelReminder"]);
if (CheckPublishedStatus(PagePublishedStatus.Published))
{
return StartPublish.AddDays(daysUntilFirstLevelReminder).ToString();
}
return "";
}
set
{
this.SetPropertyValue(p => p.CurrentReviewReminderDate, value);
}
}
EPiServer internally uses the GetPropertyValue method (i.e. the opposite of SetPropertyValue) when retrieving content for the UI.
This makes sense, otherwise your "made-up" value would be stored as the real value whenever the content is saved. This would make fall-back values etc impossible to implement.
So, this is by-design (and quite wisely so) in EPiServer. :)
However, you can customize how properties work by:
Using custom editors by applying UI hints
Modifying property metadata (for example, to display a generated value as a watermark in a textbox without interfering with the actual value being saved)
I could be misunderstanding what you're trying to do, but off the top of my head it looks like a custom editor could be a viable option for your use case?
Another solution would be to hook into the LoadedPage-event and add the value from there. This might not be the best way performance-wise since you need to do a CreateWritableClone, but depending on the site it might not matter.
[InitializableModule]
[ModuleDependency(typeof(EPiServer.Web.InitializationModule))]
public class EventInitialization : IInitializableModule
{
public void Initialize(InitializationEngine context)
{
ServiceLocator.Current.GetInstance<IContentEvents>().LoadedContent += eventRegistry_LoadedContent;
}
void eventRegistry_LoadedContent(object sender, ContentEventArgs e)
{
var p = e.Content as EventPage;
if (p != null)
{
p = p.CreateWritableClone() as EventPage;
p.EventDate = p.StartPublish.AddDays(10);
e.Content = p;
}
}
}
Using MVVM Light, it is easy to register for certain types of messages:
public MyViewModel()
{
Messaging.Messenger.Default.Register<MyObject>(this,
new Action<MyObject>((o) => DataMember = o));
}
Now, I have multiple document views in my software which implies showing/hiding views when toggling between them. When a view instance is hidden, I want its registered messages to be ignored. Similarly, when a view instance is shown, I want its registered messages to be handled. Hence, a message token per document is required:
public MyViewModel(String documentID)
{
Messaging.Messenger.Default.Register<MyObject>(this,
documentID,
new Action<MyObject>((o) => DataMember = o));
}
The problem is, I cannot figure out where in XAML/code to specify this token!
Sure, I can provide the documentID from the view...
public MyView()
{
InitializeComponent();
DataContext = new MyViewModel("1234");
}
... effectively giving me the same problem. Where would I specify this "1234" value? I read about x:Arguments Directive, hoping that it would let me specify constructor arguments in XAML, but it seems it's only supported in Loose XAML :(
I can think of a couple of solutions, like having a global variable, ActiveDocumentID, that would be used as token when instantiating the viewmodel. Is there a better solution?
I'm using WPF, MVVM and Entity Framework in my current project.
To keep things simple, let's say I have a viewmodel for CRUD operations towards a list of materials (Solid woods).
My ViewModel's EF context (WTContext) is initialized through property injection, for instance:
SolidWoods_VM newView = new SolidWoods_VM();
newView.Context = new WTContext(SettingsManager.Instance.GetConnectionString());
This way I'm able to test this ViewModel:
SolidWoods_VM swVM = new SolidWoods_VM();
swVM.Context = new FakeWTContext();
Imagine that during a insert operation something goes wrong and the WTContext.SaveChanges() fails.
What is the best way to refresh the ViewModels context?
Create a new bool property in the viewmodel named ForTestingPurposes, and when the SaveChanges method fails:
try
{
Context.SaveChanges();
}
catch
{
if (!ForTestingPurposes)
{
Context = new WTContext(SettingsManager.Instance.GetConnectionString());
}
}
Send a message to the mainviewmodel for context reloading (through mediator pattern):
Mediator.Instance.NotifyColleagues<SolidWoods_VM>(MediatorMessages.NeedToUpdateMyContext, this);
(Yet, this way I'd still need the bool property)
3.A more elegant solution, without aditional properties, provided for you guys :)
Why not abstract the methods/properties you need on your data context onto an interface and then have an implementation of that that handles the exception.
//WARNING: written in SO window
public interface IDataSource
{
void SaveChanges();
//... and anything else you need ...
}
public class RealDataSource : IDataSource
{
private WTContext _context;
public void SaveChanges()
{
try { _context.SaveChanges(); }
catch
{
_context = new WTContext(/*...*/);
}
}
}
This way you can still implement a fake/mock data source but your view model class doesn't need to know anything about how the data is actually retrieved.
My opinion is that your best bet would be the message.
You need a way to indicate that the save went wrong, and it might not serve all consumers of the class to have the context regenerated. If you're binding to your VM in there, for example, resetting the context might have other UI consequences.
I have a user control...and the base page(s) which uses this user control has a dataset which will be used by the user control.
My dataset is dynamic...means..it can have different number of columns depending upon which page my usercontrol is implemented. Is there any control in wpf which i can use to bind this dataset (without knowing the column information) ...i mean similar to datagrid/gridview in 2.0 ?
Take a look at the WPF toolkit, this contains a Grid which meets your requirements.
This toolkit is built by Microsoft, and part of the Microsoft Shared Source Initiative (see the link I provided).
It's not supported my Microsoft though, so if you get a bug you can use their forums but not call MS support.
If you do want to do it yourself, you can for example write some code that takes a List<T>, you get the generic type, get the properties, iterate over them, write the column headers, iterate over all the items in the list and write all the properties.
I wrote this code a while back to write a List to an HTML table, I hope it's useful:
public void PrintList<T>(List<T> list)
{
if(null!=list.FirstOrDefault())
{
Type t = typeof(list[0]);
PropertyInfo[] properties = t.GetProperties();
// properties = list of all properties.
print("<table><tr>");
foreach(var property in properties)
{
// print property title
print(string.Format("<th>{0}</th>", property.Name));
}
print("</tr>");
foreach(var item in list)
{
print("<tr>");
foreach(var property in properties)
{
var propertyValue = t.InvokeMember(property.Name, BindingFlags.GetProperty, null, item, new object[] {});
print(string.Format("<td>{0}</td>", propertyValue));
}
print("</tr>");
}
print("</table>");
}
}
I am converting an asp.net MVC application to silverlight, and due to the fact I was doing some 'non-standard' things in my mvc app, I am having a hard time trying to work out how to implement it in Silverlight MVVM.
Basically I was generating all my views from metadata, including links, buttons etc. One example of this that I can't get my head around how to do in Silverlight is that I passed in an action collection to my view, and had a html helper class that then converted these actions into links
public static string GenericLinks(this HtmlHelper htmlHelper, int location, bool inTable, int? parentRecordId, List<ModelAction>
actions)
{
int actionNo = 1;
StringBuilder text = new StringBuilder();
foreach (var action in actions)
{
if (action.LocationType == location)
{
if (inTable)
text.Append("<td>");
else
if (actionNo > 1)
text.Append(" | ");
text.Append(htmlHelper.ActionLink(action.Label, action.ActionTypeLookup.CodeName, new { actionId = action.ModelActionId,
parentRecordId = parentRecordId }));
if (inTable)
text.Append("</td>");
actionNo++;
}
}
return text.ToString();
}
This really worked well in MVC.
What would the equivent be in MVVM?
I would expect I could do something much more eligent, more along the lines of creating my actions in my viewmodel, and somehow binding to those actions in my view...
For something like that you would probably need to create a custom control. Then you could put it in your view and bind it to the collection of Actions which would exist in your ViewModel.