The entity framework connects to my database to retrieve columns, datatypes, relations, etc. It also knows which columns can be null and not null.
If I connect a regular asp.net grid to an entity datasource, it can generate the grid automatically based on the entity. It knows which fields should be a checkbox based on the datatype, etc.
Since data types are built into the entity class, can a regular asp.net control (like a grid or formview) also perform validation automatically? (or generate the necessary validation controls at least?)
Thanks,
Kevin
Yes, you can display validation errors including validation types using asp:ValidationSummary control. Here one project with this approach used on gridview: http://code.msdn.microsoft.com/ASPNET-Web-Forms-97f8ee9a , check out editing students.
The way to add more validation rules to entities is by attaching meta data.
If you are using EF Code First you can apply rules directly else by adding meta data class, here example:
[MetadataType(typeof(EntityNameMetaData))]
public partial class EntityName {} // name of entity which want to add validation
public class EntityNameMetaData // this is a place, where put validation rules
{
[StringLength(25, ErrorMessage = "First name must be 25 characters or less in length.")]
[Required(ErrorMessage = "First name is required.")]]
//custom or other validation rules
public String EntityProperty
}
this is not possible automatically in asp.net, you would have to define the columns and create item templates to implement this.
Related
I am trying my hands on MVC 2, ADO.NET EF and POCO. I have generated my entity classes in a separate library using POCO generator.These POCO entities are used as ViewPages (Not sure if that's the right way to design or do I need separate ViewModels classes ?)
Now, if I take case of a simple scenario where I need to add an Employee object( which is related to a Department Master), what then should be the recommended way to transfer these objects between layers.
Layered structure of the application is somewhat like this :
I have thought of various alternatives:
I have a method in the Employee Controller which is named AddEmployee() which accepts the FormCollection as parameter. Within the form collection I get posted data such as Employee Name, Age , Salary etc and the ID of the Selected Department .
1.) One way is that I can create another DTO say EmployeeDepartment DTO which will be used to map values from FormCollection as is. I can then break them at manager layer and use them to create entity objects i.e Employee Object and refer department by query similar to this:
e.Department = Department.where(i => i.deptId == empDepDto.dept_id).first()
I am not a big fan of this and feel that every time there is a relation involved I have to add a DTO and then map it to my entity class.
2.) Second is probably the worst, i.e passing each object as parameter and then couple them in manager layer.
3.) Use POCO as is, Create a Employee Object and Deparment Object at controller layer and pass the POCO object
public void AddEmployee(FormCollection formCollection)
{
Department d = new Deparmtent; d.id = ""; //based on the dropdown value
d.name="" //based on the dropdown selected text;
Employee e = new Employee; e.Name. e. sal....
e.Department = d;
EmployeeManager.AddEmployee(e);
}
But at manager layer I think , I still need to recreate the reference to the Department using LINQ which again is repetitive and doesn't seems to be a clean solution.
Are there better ways of handling this ? Looking for recommendations and best practices.
Firstly, is there any reason you're not using MVC version 3? There's no major breaking changes, so may as well upgrade?
Secondly is there a reason for using FormCollection rather than the strongly typed model-binding? Just change your views to use the strongly typed HTML helpers ( like <%: Html.TextBoxFor(m => m.Property) %>), or make sure the name attributes match the property names, and have your controller receive the type, and model binding will do the rest. There's plenty of tutorials showing this, and articles explaining it. Model binding will work with a name/value collection, like that posted as a form, or against JSON data, or you can find/write custom model binders that work against whatever wacky serialisation protocol you want.
One thing to watch though when passing the actual entity types that Entity Framework will store around, is that you have to be careful when updating existing objects, or with foreign key references to existing objects - all your objects must be attached to the right Entity Framework context. To achieve that you will often see the objects received by the controller having their properties copied to a freshly retrieved entity from a context, either manually or by an object mapper of some kind.
Make a seperate project called "BusinessObjects" or "Model" which contains your POCOs. Then use strongly typed model-binding for MVC and you'll be set.
The method signature will look something like this:
// In your Controller
public void AddEmployee(Employee newObject)
{
YourDataContext dc = new YourDataContext();
dc.Employees.Add(newObject);
dc.SaveChanges();
}
I'm working on an ASP.NET MVC3 application and I annotated my model with an attribute that specifies what roles can change specific fields for any possible status the model is in. Take this as an example:
public class Model
{
[RoleLimiter(
new[]{Role.Admin, Role.BasicUser, Role.Validator}, // for draft
new[]{Role.Admin, Role.BasicUser, Role.Validator}, // for awaiting validation
new[]{Role.Admin})] // for published etc
public string Subject {get;set;}
}
It looks a bit messy, sure, but it's very easy to change if needed. Now once I have this, it's easy to check for each field the current status and then get the list of roles that can change it. If the current role isn't in it, I'll add a disabled class to the control.
What I wanted to do next is to make a HtmlHelper extension that has the same syntax as the normal EditorFor (or even a straight-forward TextBoxFor), but does this extra check and automatically adds the attribute behind the scenes, but I'm stuck on getting the field info from the expression, ie:
How do you get from
HtmlHelper.TextBoxWithRoleLimitationsFor(x=>x.Subject);
to the attribute attached to x.Subject?
You fetch the LambdaExpression.Body and check whether it's a MemberExpression. You can then get the Member of the MemberExpression and get the custom attributes from that.
I've been chugging along OK with the use of data annotations made on buddy classes so far.
When it comes to a more complex view that requires a custom view model--one that includes a few select lists, for example...would I need to then transfer my validation attributes to the view model class?
I was planning to pass the full custom view model to populate an "Edit" view, but was hoping to just receive a simple object in my "Save" action.
Where are the flaws in this plan, or is the whole thing just one big pile of fail in the first place?
Thank you.
You're still validating that data that is ultimately going back into the database. So in order to keep your application DRY, you are best off to use the Buddy Classes for the original Model.
Edit
note: this doesn't exactly have anything to do with your question
I personally prefer extend the original Model for anything "Edit" related and I prefer to use a ViewModel for "Display" only (Details pages, List pages, etc).
Example: here's my buddy class, and in it I've added a "RegionName" property that I use in the Edit Page display, but it doesn't have anything to do with the database. You can do a similar thing with custom input data that you want to validate before manipulating it into "database usable" data. I use the RegionID in the database, but I prefer to use the friendly name for the visitor instead of the ID integer
<MetadataType(GetType(UserMetaData))> _
Partial Public Class User
Public RegionName As String
End Class
Public Class UserMetaData
<DisplayName("region name")> _
<Required(ErrorMessage:="region name is required.")> _
Public Property RegionName As String
End Class
Your view model will still inherit the validation from your base model.
Don't know if this helps but I put my validation attributes against my model so that wherever i use the model i get the same validation. not ideal for some projects i realise.
actually, i put the attributes agains a partial class rather than my model because 90% of the time my model comes from a linq 2 sql file in my data repository
my controller then simply checks if the model is valid or not and the view does nothing except display data and errors really.
unsure if this is what you're asking though
We know that authorization's stuff is a cross cutting concern, and we do anything we could to avoid merge business logic in our views.
But I still not find an elegant way to filter UI components (e.g. widgets, form elements, tables, etc) using the current user roles without contaminate the view with business logic. same applies for model binding.
Example
Form: Product Creation
Fields:
Name
Price
Discount
Roles:
Role Administrator
Is allowed to see and modify the Name field
Is allowed to see and modify the Price field
Is allowed to see and modify the Discount
Role Administrator assistant
Is allowed to see and modify the Name
Is allowed to see and modify the Price
Fields shown in each role are different, also model binding needs to ignore the discount field for 'Administrator assistant' role.
How would you do it?
On way I could think to do this is create your own versions of the input extension methods. For example instead of TextBox you could create TextBoxRoles and define it like this:
public static MvcHtmlString TextBoxRoles(
this HtmlHelper htmlHelper,
string name,
string RolesEdit,
string RolesView
)
Then in code it would look like this:
<%= Html.TextBoxRoles("Price", "Administrator","Administrator,Assistant") %>
Then your implementation of TextBoxRoles would check the roles of the current user via User.IsInRole() to determine what should appear on the page.
Of course you would have to do this for every input extension method you use.
Since you already have both the current user and access to the authorization provider in your controllers this is an ideal responsibility for them. Using a naive implementation you might pass a collection of widgets to your view after you filtered which widgets the current user has access to. In the case of your form field, things might get hairy when you consider client side validation.
The binding part would be the most straight forward of all, having a custom binder for these special cases will do the trick specially well since it will have access to the controller context and you can grab the current user from there and bind the values according to your role definitions.
What about something like LinFu, an AOP framework? If it's crosscutting, then declare it is so and treat it as such.
I am trying to display a 'Software Release' table in an asp.net dynamic data site. The Release table has a build number stored as three int fields (Major, Minor, Build). I'm using EntityFramework, so I have an EF model bound to my database schema. In my dynamic data site, I want the build number to show up as a single field (Major.Minor.Build) wherever the Release object is shown (particularly when it shows as a foreign key on pages for related objects). Since this 'computed column' is not a field in my database, there doesn't seem to be anyway to get the Dynamic-Data to recognize or display it. I can add a property to the Release object (since it is a partial class generated by EF), but Dynamic-Data won't recognize it, because it isn't a 'column'. I want to edit the Release as three separate fields (major, minor, build), but when it is displayed, I want it to show as a single field. The DynamicData framework doesn't seem to support composite fields, and it won't display/bind to properties on the object if they aren't in the EF model. How do I make the formatted version number property the default display value?
You can add an metadata class as you would when doing any dynamic data ui customization.
Then you create a UIHint in the metadata to tell the dynamic data what control to use for your custom object.
E.G.
[MetadataType(typeof(EMetadata))]
public partial class E{
public string RefNR {
get {
return "E" + this.EntryID.ToString().PadLeft(5, '0');
}
}
}
public partial class EMetadata {
[UIHint("Text")]
public object RefNR;
}
I'm not sure if you are binding to a DataTable/DataSet returned from the database, or if you are binding to a Release object itself. Nor which kind of control.
If you are binding to a DataSet/DataTable, simply change your SQL to return the version as one field:
SELECT table1.Major + '.' + table1.Minor + '.' + table1.Build AS Version ....
However, if you are binding to an object to, say, a DropDownList, I think that if you override the ToString method, it will become the Display value in the DropDownList:
Public Overrides Function ToString() As String
Return _major.ToString & '.' & _minor.ToString & '.' & _build.ToString
End Sub