I'm very impressed with MonoTouch.Dialog by Miguel. inspired by his simple approach I thought it would be very nice to have a reflection based NSUserDefaults class that works seamlessly by marking certain properties as "persistable in user defaults" and forget about the rest. something like this:
public class SomeController
{
[PersistInUserSettings]
public string LastPostUserRead { get; set; }
}
I don't like the LastPostUserRead to be of type "UserSetting", I like it to be a normal property so that later I can assign to it like:
LastPostUserRead = "Post 1";
and not like:
LastPostUserRead.SetValue("Post 1");
Any idea on how to implement it (without Reflection.Emit) in monotouch?
You do not need Reflection.Emit at all to dynamically set values. That is pure System.Reflection (without the "Emit" part).
MonoTouch.Dialog in fact reads and stores values dynamically using SetValue and GetValue from the FieldInfo (could be done for properties too).
Related
I've got a POCO defined, something like this:
public class Customer
{
public string Name { get; set; }
public DateTime DOB { get; set; }
[System.ComponentModel.DataAnnotations.Schema.NotMapped] // <- this is what I want to do, but can't in PCL
public AccountCollection Accounts { get; set; }
}
The above has the "NotMapped" attribute, which is what I want - but it's not available in a portable class library (PCL). The thing is, the class I need is defined in an assembly that WILL be used on the portable device but it will be filled from entity framework on the web, which DOES have access to the NotMapped attribute. If I could find a way to add the property to EF's "NotMapped" list, that would be ideal.
Is there a way to get this to work? That is, a way to do what "NotMapped" does programmatically?
I've considered other workarounds, but none of them are ideal:
Could create a DAL separate from my domain layer and translate
between the two (but requires mapping and two models instead of one)
Could write custom EF queries and updates to ignore the property (but means writing all the linq/SQL/procs myself)
Found the answer in the Context's OnModelCreating() overload. Accessing the modelBuilder parameter it's possible to find the entity and ignore specific properties. This works even when the POCO is defined in a PCL.
For example:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
// Ignore Customer.Accounts
modelBuilder.Entity<Customer>().Ignore(c => c.Accounts);
}
I am using Xamarin.iOS. I have created UIView with a few UITextFields. I am looking for best way to initialize text value in these textfields from code.
I can pass text data in the constructor of UIViewContoller, but I don't have access to textFields inside it (they are null). I can change text value of textFields in viewDidLoad method.
I don't want to create additional fields in controller class to store data passed by constructor and use them in viewDidLoad. Do you know better solution ?
I don't want to create additional fields in controller class to store
data passed by constructor and use them in viewDidLoad.
But that's how it's meant to be done.
Alternatively, you can create less fields/properties in your viewcontroller if you use a MVVM pattern:
public class UserViewModel {
public string Name { get; set;}
public string Title { get; set;}
}
public class UserViewController : UIViewController
{
UserViewModel viewModel;
public UserViewController (UserViewModel viewModel) : base (...)
{
this.viewModel = viewModel;
}
public override void ViewDidLoad ()
{
userName.Text = viewModel.Name;
userTitle.Text = viewModel.Title;
}
}
That's the kind of pattern which gives you a lot of code reuse accross platforms (android, WP, ...) and clearly separate concerns. It's a (very) little bit of extra code, but it's worth every byte.
whats difference between Auto-Implemented Properties and manual properties in c#?
for Example:
Manual Properties:
private int uno;
public int Uno
{
get { return uno; }
set { uno = value; }
}
Auto Implemented Prop:
public string UserLeaveCount { get; set; }
i found the difference and uses here : Auto Implemented Prop
But Here is my Specific doubt thats "there is no instance variable in auto implemented properties and how is it stored,returned values?"
It's just syntactic sugar -- the compiler inserts the backing field for you. The effect is the same, except that, of course, there's no way for you to access the backing field from your code.
From the page you linked to:
When you declare a property as shown in the following example, the compiler creates a private, anonymous backing field that can only be accessed through the property's get and set accessors.
I've been reading up on PostSharp, and I want to use introduction to inject a member. For a stupid example, say I write an aspect that introduces
public Guid Id = Guid.NewGuid();
Easy enough, if i disassemble, I see its there. Now the tricky part.. within the same class, I'd like to do something like;
public void PrintGuid()
{
Console.WriteLine(this.Id);
}
How would I do this? Alternately, if that doesn't work, can I do something like declare the variable in the class, and then use it in the aspect? So the class would have
public Guid Id;
And the aspect would do something like
this.Id = Guid.NewGuid();
You can see how to do it here
http://www.sharpcrafters.com/blog/post/PostSharp-Principals-Day-14-e28093-Introducing-members-and-interfaces-Part-1.aspx
http://www.sharpcrafters.com/blog/post/PostSharp-Principals-Day-15-e28093-Introducing-members-and-interfaces-Part-2.aspx
If you need to use it at design time then you probably shouldn't be introducing it at compile time. Either change it to be there at design time or you can abstract an interface and use Post.Cast<>() to take advantage of it
var MyClass = Post.Cast<IMyInterface>(...);
MyClass.MyIntroducedMember = 10;
There are a lot of workarounds for the missing support of enumerations in the Entity Framework 4.0. From all of them I like this one at most:
http://blogs.msdn.com/b/alexj/archive/2009/06/05/tip-23-how-to-fake-enums-in-ef-4.aspx?PageIndex=2#comments
This workaround allows you to use enums in your LINQ queries which is what i exactly need. However, I have a problem with this workaround. I get for every complex type I'm using a new partial autogenerated class.Therefore the code does not compile any more because I already have a wrapper class with this name in the same namespace which converts betwen the backed integer in the database and the enum in my POCO classes. If I make my wrapper a partial class, the code still does not compile as it now contains two properties with the same name "Value". The only possibility is to remove the Value property by hand everytime I generate the POCO classes because the DB model changed (which during the development phase happens very often).
Do you know how to prevent a partial class to be generated out of complex property everytime the EF model changes?
Can you recommend me some other workarounds supporting enumerations in LINQ queries?
That workaround is based on the fact that you are writing your POCO classes yourselves = no autogeneration. If you want to use it with autogeneration you must heavily modify T4 template itself.
Other workaround is wrapping enum conversion to custom extension methods.
public static IQueryable<MyEntity> FilterByMyEnum(this IQueryable<MyEntity> query, MyEnum enumValue)
{
int val = (int)enumValue;
return query.Where(e => e.MyEnumValue == val);
}
You will then call just:
var data = context.MyEntitites.FilterByMyEnum(MyEnum.SomeValue).ToList();
I am using an approach based on the one described in your link without any modifications of the T4 templates. The contents of my partial wrapper classes are as follows:
public partial class PriorityWrapper
{
public Priority EnumValue
{
get
{
return (Priority)Value;
}
set
{
Value = (int)value;
}
}
public static implicit operator PriorityWrapper(Priority value)
{
return new PriorityWrapper { EnumValue = value };
}
public static implicit operator Priority(PriorityWrapper value)
{
if (value == null)
return Priority.High;
else
return value.EnumValue;
}
}
I've only changed that instead of a back store variable with enum value I am using the autogenerated int typed Value property. Consequently Value can be an auto-implemented property and EnumValue property needs to do the conversion in getter and setter methods.