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MVC scaffolding is duplicating my model fields

I seem to be running into a weird issue and after hours of head scratching, I seem to have narrowed the issue down to a combination of partial classes and virtual properties. When I override a property that's in a partial class, sitting in a separate file, MVC duplicates the fields on my view. I am using Visual Studio 2013 and the issue can be duplicated by following these steps:
Open Visual Studio and create a new Project. Choose Web under the categories, then choose "ASP.NET Web Application". I am targeting .NET 4.5.
Choose "Empty" from the template selection, then check the MVC checkbox so it adds the core folders and references.
Once the project is created, right-click on the Models folder and create a new class called MyModel.cs.
Add these lines to the new file:
public abstract partial class MyOriginalModel
{
public virtual string FirstName { get; set; }
public virtual string LastName { get; set; }
}
public partial class MyModel : MyOriginalModel
{
}
Now right click on the Models folder again and create another new class called MyModelCustom.cs.
Add these lines to the file:
public partial class MyModel
{
[System.ComponentModel.DisplayName("First Name")]
[System.ComponentModel.DataAnnotations.Required]
public override string FirstName
{
get
{
return base.FirstName;
}
set
{
base.FirstName = value;
}
}
[System.ComponentModel.DisplayName("Last Name")]
[System.ComponentModel.DataAnnotations.Required]
public override string LastName
{
get
{
return base.LastName;
}
set
{
base.LastName = value;
}
}
}
Now build the project, then right click on the Controllers folder and add a new controller. Choose "MVC 5 Controller with read/write actions" and call it NamesController. Right click on the Create method and go to "Add View". Under the template dropdown, choose Create and for the Model Class dropdown, choose MyModel.
Once MVC creates the template, you will see that it adds First Name and Last Name twice. The issue seems to be related to partial classes because if I move the contents of MyModelCustom.cs into MyModel.cs, everything works fine. However, its not just partial classes. If I create a new property (versus overloading one) in the partial class, it does not duplicate that property. So it seems to be a combination of partial classes and overriding virtual properties.
Can someone please confirm if this is a bug or if I am doing something wrong?

It is a bit of both. Bug or not, if MVC is scaffolding incorrectly, you will either have to constantly fight the framework or change your approach to the problem.
As a general rule, I've found that when you have to fight the MVC framework to make it behave the way you want, then it is far easier to change your approach to the problem. Otherwise, you will end up fighting that particular battle repeatedly until you eventually comply. Take it from someone who's learned that lesson the hard way.
With easier approaches in mind, here are a few things you could try instead:
If you are overwriting a lot of properties, create separate classes with common names for properties (FirstName, LastName). Then use Best way to clone properties of disparate objects to marshall the data between objects.
You could also use Fody PropertyChange listeners to handle whatever logic is needed when these values are changed thereby eliminating the need for the partial overrides entirely.
A final option would be to override the scaffolding templates to skip overridden properties. Not sure how you would detect that though.

Take a look at CodePlex source for MvcScaffolding EnvDTETypeLocator.cs
/// <summary>
/// Out of a set of CodeType instances, some of them may be different partials of the same class.
/// This method filters down such a set so that you get only one partial per class.
/// </summary>
private static List<CodeType> PickArbitraryRepresentativeOfPartialClasses(IEnumerable<CodeType> codeTypes)
{
var representatives = new List<CodeType>();
foreach (var codeType in codeTypes) {
var codeClass2 = codeType as CodeClass2;
if (codeClass2 != null) {
var matchesExistingRepresentative = (from candidate in representatives.OfType<CodeClass2>()
let candidatePartials = candidate.PartialClasses.OfType<CodeClass2>()
where candidatePartials.Contains(codeClass2)
select candidate).Any();
if (!matchesExistingRepresentative)
representatives.Add(codeType);
} else {
// Can't have partials because it's not a CodeClass2, so it can't clash with others
representatives.Add(codeType);
}
}
return representatives;
}
}
:
:
1) PickArbitraryRepresentativeOfPartialClasses, the method uses Linq any() to confirm that the codeType as CodeClass2 has members.
CodeClass2 is the partial class type of EnvDTE, Visual Studio's core Automation library responsible for IDE code generation (Design Time Reflection).
2) If the class cast as CodeClass2 does have members, the class is added to the representatives
3) When the partial class is evaluated, each file will be visited within a distinct context (often leading to a consolidation of elements that should be overridden)
An interesting distinction between Run Time Reflection and Design Time Reflection: sic
An ASP.NET control has two distinct sets of functionality for when it is executed at run-time inside a page or used at design-time inside a host designer. Run-time capabilities determine, based on configuration, the markup that is output by the control. The design-time capabilities, instead, benefit of a visual designer such as Microsoft Visual Studio 2005. Design-time capabilities let the page author configure the control for run-time in a declarative and WYSIWYG (what-you-see-is-what-you-get) manner.
Conclusion:
MVC Scaffolding does use reflection, but it is the much less reliable Design Time Reflection.
Design Time Reflection is not the same as Run Time reflection. A fully compiled Class is a final result of inheritance resolves and partials combined and priority resolved. Design Time Reflection makes best guesses about how to work with complex, multi-part types.
If you want to rely on Scaffolding, better not to push it's limits. When you get errors like this, try simplifying your ViewModels:
Try consolidating your partial classes
Try removing your abstracts / virtuals

Entity Framework adding functionality to Properties

In an old WPF project I have a class with Properties like this:
private string _name = "";
public string Name
{
get { return _name; }
set
{
string cleanName = clsStringManip.CleanText(value, true);
if (cleanName != _name)
{
_name = cleanName;
}
}
}
Where every time the name changes, I ensure that the value is "cleaned". Putting it in the property ensures I never forget to clean the string before setting the property on the object.
Now I am recreating this system using MVC5 and EntityFramework6.1 using DatabaseFirst.
So all the properties are autogenerated by EF. How then can I add the equivalent CleanText function to my properties without editing the autogen code? - as I'll lose these changes next time I change my database and resync.
All I can find via Google is a way add data annotations via MetadataType and partial classes but this doesn't answer my question.
I tried to add the above code into a partial class but get the error:
The type XXX already contains a definition for Name
The only way I can think is to create a bunch of SetProperty() functions but this is dirty and you can never ensure other developers (or myself) will remember to use them.

Disclaimer: I haven't used EF 6 yet.
Let me answer this in two parts. First, I will tell you how to do this. Then I will tell you why I don't think you should do this. :-)
HOW:
As you discovered, you cannot create another Name property. You need to modify the way the EF generates the code, so that it gives you a place to insert your new code. Depending on how you are using the EF, it often generates Validate() method calls or OnPropertyChanged() calls. You may be able to do what you want inside of those methods.
If you can't do this in Validate() or OnPropertyChanged(), you could change the T4 template to generate something like this:
private string _name = "";
public string Name
{
get { return _name; }
set
{
string cleanName = value;
Cleanup_Name(ref cleanName);
if (cleanName != _name)
{
_name = cleanName;
}
}
}
private partial void Cleanup_Name(ref string);
This gives you a partial method that you can then implement as you see fit. So for any property you want to customize, you can now add another file to your project that does this:
public partial class MyEntity {
void Cleanup_Name(ref string name)
{
// Put your logic in here to fixup the name
}
}
If you do not write the above code block, then the partial method is simply a no-op. (Partial methods must return void, hence the use of a ref parameter).
WHY NOT?
The advantage of this method is that it is totally transparent to the developer. The property is just magically changed. But there are several disadvantages:
Some controls expect that if they call name = "123" that if they get the name back, it is "123" and will fail if this happens. Values are changing but no PropertyChanged event fired. If you do fire the PropertyChanged, then they sometimes change the value back. This can cause infinite loops.
There is no feedback to the user. They typed in one thing, and it looked right, but now it says something different. Some controls might show the change and others won't.
There is no feedback to the developer. The watch window will seemingly change values. And it is not obvious where to see the validation rules.
The entity-framework itself uses these methods when it loads data from the database. So if the database already contains values that don't match the cleanup rules, it will clean them when loading from the database. This can make LINQ queries misbehave depending on what logic is run on the SQL server and what logic is run in the C# code. The SQL code will see one value, the C# will see another.
You might also want to look into what the Entity-Framework's change tracking does in this case. If a property set does a cleanup while loading values from the database, does it consider that a change to the entity? Will a .Save() call write it back to the database? Could this cause code that never intended to change the database to suddenly do so?
ALTERNATIVE
Instead of doing this, I suggest creating a Validate() method that looks at each property and returns errors indicating what is wrong. You could also even create a Cleanup() method that fixes the things that are wrong. This means the cleanups are no longer transparent, so the developer must call them explicitly. But that is a good thing: the code isn't changing values without them realizing it. The person writing the business logic or the UI knows at what point the values will change, and can get a list of why.

The only way you can achieve this is by creating a new property you actually use in your application. Perhaps you can hide the original property in the designer. The actual property you use could look like this:
public string ExternalName
{
get { return Name; }
set
{
string cleanName = clsStringManip.CleanText(value, true);
if (cleanName != Name)
{
Name = cleanName;
}
}
}
As an alternative, you can use POCO classes:
If you want to keep using database-first, check this answer
Use code-first for an existing database, see this detailed guide

Add partial to the generated class.
Change the scope of Name in the generated class from public to internal.
Add the following in the same assembly:
public partial class classname
{
[NotMapped]
public string CleanName
{
get { return Name; }
set
{
var cleanName = clsStringManip.CleanText(value, true);
if (cleanName != Name)
Name = cleanName;
}
}
}
Caveat: you'd have to remember to do steps 1-2 every time you regenerated your POCOs ... I'd seriously consider Code First to Existing Database.
EDIT
Optionally:
Rename Name as InternalName in the generated classname; decorate it with [Column("Name")].
Rename CleanName as Name in the partial class under your control.
Caveat in 4 becomes "remember to do steps 1, 2, and 5 every time you regenerate POCOs".
This approach has the added benefit of not having to modify any of your client code (i.e., use of Name remains Name). And I'd still strongly consider Code First to Existing Database.

Monotouch set properties not keeping property values

In my MonoDevelop project I have an iPhone app. I have two different views. Each view contains a UITable. For view 1 I have class 1 hooked to the UITable as Datasource 1. For View 2 I have a class 2 hooked up as Datasource 2. Both classes (i.e. Datasources) feed the tables with data. View 2 also has a custom cell and because of this loads asynchronous.
I get the data from 2 XML files using linq to XML. Everything works and the data loads great. What I need to do know is to load data in Datasource 2 based on the selection made in View 1. To do this I need to pass an ID from view 1 to Class(Datasource) 2. Problem.
I have tried just about everything I know but I just can't get it right.
The correct solution according to me:
I have created another class called SelectedRound with two properties. Code:
using System;
namespace xxxxx
{
public class SelectedRound
{
public string RoundID { get; set; }
public string Date { get; set; }
}
}
When I set RoundID in class 1 then I can access it in class 1. Trying to access it in class 2 however, returns nothing or null. Why would this happen? Could it be because Class(Datasource) 2 is loading asynchronously? Should I instantiate the SelectedRound class in some global way? If so how? AppDelegate maybe? (I am struggling to do that as well).
It seems pointless to me that setting and getting a simple string variable is difficult.

This feels like it is all about how you are passing the SelectedRound instance from the first view to the second.
As a very quick and dirty solution you could just use a singleton or could just use a static class:
public static class SelectedRound
{
public static string RoundID {get;set;}
public static string Date {get;set;}
}
For a more sophisticated pattern, then try overriding the constructors of one or both of your two view controllers in order to pass them a shared instance of your non-static class.
The view controllers may feel foreign to you right now - but they are just c# classes - so feel free to extend them by writing overrides, new methods and properties.

How to add properties to a Form on a group, and show in Properties Windows and be editable

I have this class:
public class MyProps
{
public MyProps()
{
}
protected string myVar;
public string MyProperty
{
get { return myVar; }
set { myVar = value; }
}
protected int myOtherVar;
public int MyOtherProperty
{
get { return myOtherVar; }
set { myOtherVar = value; }
}
}
That I want to add to my Form, so when I inherit from it I will be able to fill the properties in the MyPropsX property.
I have this code in my form:
protected MyProps propsX = new MyProps();
[TypeConverter(typeof(ExpandableObjectConverter))]
public MyProps MyPropsX
{
get
{
return propsX;
}
set
{
propsX = value;
}
}
Now, the properties MyProperty and MyOtherProperty are nicely shown in the Properties Window, and I can set their values directly there.
But when I close my form and I open it again, all my changes are lost, the properties being reset to show zero and an empty string.
What am I missing?
Should I inherit my MyProps class from certain special class or interfase?
Or some special attribute?

This is a little bit much for a comment and maybe your solution, so i'm answering to your comment with an answer instead with another comment:
With does not happen when I put properties directly on a form you mean, you are using the designer to set some property of the form. These will be written into the MyForm.designer.cs file. When you go into the code of your class you'll find within the constructor a method InitializeComponent(). Set the cursor on it an press F12. Here you can see what the designer has written into all the properties. You should respect the comment above the mentioned method and not start to modify the code with the code editor unless you really have understand how and when the designer will read and write code here (which is another chapter i can explain if needed). Otherwise it will happen that trying to opening your form with the designer after the code change will lead to an error message or code loss.
If you like to set some default value also, you should go back into the constructor and add the needed initialization code below the InitializeComponent() function and everything should work as expected.
Update
As you wrote in your comment you already know how the Designer interacts with the *.designer.cs file. So i really can't understand your concrete problem but maybe one of these articles can give you a more insight about how Microsoft wrote their components:
Make Your Components Really RAD with Visual Studio .NET Property Browser
Components in Visual Studio

This is very normal, since each time you are closing the form and opening it again you are having a new instance from the form MyPropsX, so the best way would be to save your properties in any kind of a database (sql, access, textfiles,...)

ObjectDataSource - Can your load methods reside in a different class to the entity?

I have the following class model:
public class Person
{
public string Name;
public int Age;
}
public class PersonService
{
public List<Person> GetAll() {...}
}
I'm displaying the data on an ASP.Net web page by binding an ObjectDataSource (ODS) to a GridView.
If I point the 'ODS.TypeName = PersonService' then it gives an "Object does not match target type." error on loading data.
If I point the 'ODS.TypeName = Person' then it can't find the GetAll() method to load data.
Is it possible to bind the ODS to this model (i.e. separate classes for the method and type)?
Edit: I've double checked Type and Select method names are correct (and fully qualified). I made a separate quick test project to prove ODS works with the above model - it does. The only difference now, is that the broken project is using an Entity defined by EF 4.1 - would that cause a problem?

TypeName needs to be set to PersonService in your example. There is no need to provide the ODS with the exact type of object bound to the grid's rows (Person in your example), as neither ASP.NET data binding nor the ODS/grid will really care. Concerning your error, try to fully qualify the service, e.g., My.Namespace.PersonService, and make sure to set SelectMethod on the ODS accordingly.

I think you want to create a PersonList class that exposes a list of Person object and which has a method uses PersonService to populate/return a list.

enter image description here
Just right click on your project and select "Disable Lightweight Solution Load"
it will work. there is no other issue