Is there any way to access the Class and Property name which you attached an attribute to inside the attribute?
For example
public class User {
public string Email { get; set; }
public string FirstName { get; set; }
[MyAttribute]
public string LastName { get; set; }
}
And then in the MyAttribute class
public class MyAttributeAttribute {
public MyAttributeAttribute () : base() {
string className = /*GET CLASS NAME - should return "User" */
string propertyName = /*GET PROPERTY NAME - should return LastName*/
}
}
I know I can pass in the information in the constructor, but hoping there is an easy way somehow to save on retyping info over and over again either via reflection or...
Sorry, but no that's not possible. You could also have
public class User {
public string Email { get; set; }
public string FirstName { get; set; }
[MyAttrubute]
public string LastName { get; set; }
}
[MyAttrubute]
public class OtherClass {
[MyAttrubute]
public string AnotherProperty { get; set; }
}
The attribute can be created from anywhere. Even the following is a valid way to create an instance:
var att = new MyAttribute();
Your question could be boiled down to "Can I detect where my custom class is instantiated from?". In my last example, StackTrace could probably be used. But with attributes they are being constructed by the .NET runtime, so you would not be able to go that route.
Related
What I want
I want to send a limited/reduced class/object to frontend (as JSON). I use .NET Core 5.
What I have
I have a model class like this:
namespace Tasks.Models
{
public class Resources
{
public Guid Id { get; set; }
public string Type { get; set; }
public string Url { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public DateTime? Createdon { get; set; }
public Guid Userid { get; set; }
public Guid Taskid { get; set; }
public int Clicked { get; set; }
public byte Active { get; set; }
+++ many more properties
}
}
Now depending on the which controller that calls this model I want to have different "kind" of models. So if the resource is file I maybe want the properties Id,Type,Name. But if the resource is URL I want Id, Url, Name.
I tried setting up a method that "initialized the fields I wanted, but that also returned all properties
public static Responses FileResponse()
{
var response = new Responses()
{
Id = new Guid(),
Name = "",
Type = "File",
};
return response;
}
Now, when I call the Resources class or this method I get all properties, and returning it to the view presents all properties, but mostly as null, because I only set the three fields in the method.
What is the recommended way of solving this?
If you want to remove the field if it's null instead of showing in json with null value.
public class Resources
{
public Guid Id { get; set; }
public string Type { get; set; }
// if null, dont show it in JSON output
[JsonIgnoreAttribute(Condition = JsonIgnoreCondition.WhenWritingNull)]
public string Url { get; set; }
// if null, dont show it in JSON output
[JsonIgnoreAttribute(Condition = JsonIgnoreCondition.WhenWritingNull)]
public string Name { get; set; }
public string Description { get; set; }
public DateTime? Createdon { get; set; }
public Guid Userid { get; set; }
public Guid Taskid { get; set; }
public int Clicked { get; set; }
public byte Active { get; set; }
}
PS: Fiddle https://dotnetfiddle.net/hiMAci
It is just limiting the Resource class I am not able to do
Yep, side effect of C# being strongly typed, with object X definitely having properties Y and Z. You need differently shaped objects - either full on classes or records - that name the reduced set of properties because the serializer is going to look a tthe object and ser every property it can find.
You could make a new class for every variation - quick and easy with records, and easy to pass around inside your C#:
public record FileThing(string Id, string Type, string Name);
//make a new one and return it
new FileThing(someResources.Id, someResources.Type, someResources.Name);
Or can consider using an anonymous type if you're literally looking to put a few properties into some json, down a socket to a consuming front end (I can't quite decide what you mean by "view" - it doesn't seem to be an MVC View) that only cares about a few props out of many
So if the resource is file I maybe want the properties Id,Type,Name. But if the resource is URL I want Id, Url, Name.
public ActionResult SomeControllerMethod(){
if(isFile)
return Ok(new { someResources.Id, someResources.Type, someResources.Name });
else if(isUrl)
return Ok(new { someResources.Id, someResources.Url, someResources.Name });
}
Anonymous types are a bit harder to work with because the compiler writes the class for you, so it's tricky to do things like declare return types from methods if the method is returning an AT.. But if you're using it as some fill-in all within one method, such as a "make this and serialize it", they work well..
I think your approach is not the right one here. I tend to follow more general OO guidelines in this situation (note, some consider these a bit dated, and other solutions exist. But they are still commonly used)
You write against an interface. So let's see what you want... A guid, type and name. All other deatils aren't important.
public interface IResourceDetails
{
public Guid Id { get; }
public string Name { get; }
public string Type { get; }
}
And you can have multiple of these interfaces.
You could then implement the interfaces per type. But I would probably combine them in a base class
public abstract class ResourceBase : IResourceDetails
{
public Guid Id { get; } = new ();
public string Name { get; init; }
public string Type { get; }
public ResourceBase(string type)
{
Type = type;
}
}
Each resource type would have it's own implementation
public class FileResource : ResourceBase
{
public FileResource() : base("File") { }
// File-specific properties.
public string Description { get; init; }
public DateTime? Createdon { get; init; }
}
The response method then could be made generic and look like this
public static IActionResult Response(IResourceDetails resource)
{
return Ok(new
{
resource.Id,
resource.Name,
resource.Type,
});
}
There is the following class:
public class A
{
[Required]
public string property { get; set; }
}
and it's used by another class like:
public class B
{
public A prop { get; set; }
public A prop2 { get; set; }
}
in my scenario, B.prop.property should be required while B.prop2.property should not be [Required].
Is there a way to override prop2.property attribute to be not required? and it also should affect the record recorded in the Database?
if not what is the most recommended practice to deal with such issue?
No. There is no way to achieve what you're talking about. You can do so via inheritance. For example:
public class C : A
{
public new string property { get; set; }
}
Then:
public class B
{
public A prop { get; set; }
public C prop2 { get; set; }
}
In other words, the property must literally be a type where that property is not required. You can't just disable an attribute on a class instance at a whim.
I'm reading user input from different types of CSV files having a few common and a few different attributes. I have created a base class TestCaseData and derived classes as below:
public abstract class TestCaseData
{
public abstract string ID { get; set; }
public abstract string Name{ get; set; }
}
public class DerivedClassOne :TestCaseData
{
public override string ID { get; set; }
public override string Name{ get; set; }
pubic string DerivedOneProperty{ get; set; }
}
public class DerivedClassTwo :TestCaseData
{
public override string ID { get; set; }
public override string Name{ get; set; }
pubic string DerivedTwoProperty{ get; set; }
}
I am reading the CSV file and creating a list of derived classes and assigning to list of base class as below
List<TestCaseData> lstTestCaseData = MethodCallToReturnListOf_DerivedOneClassFromCSV();
As now I have lstTestCaseData I have to validate the user inputs also where I am unable to find a way to write a single method to validate user input of type DerivedOneProperty or DerivedTwoProperty as they have their own properties. Anyone can help me here?
I have method signature something like that
public string ValidateCompleteFile(List<TestCaseData> TestCaseInputList, out bool IsInputValid)
You could instead put an abstract validation method on the TestCaseData class and then let each class that inherits this class implement it how they need to.
public abstract class TestCaseData
{
public abstract string ID { get; set; }
public abstract string Name{ get; set; }
public abstract bool Validate();
}
And then call this method for each entry in the TestCaseInputList collection.
The answer regarding an abstract method is the best solution if you're committed to the code pattern you originally conceived of (i.e. calling a validation method on each object). But perhaps it would be better to validate each field in its setter:
public abstract class TestCaseData
{
private string id, name;
public abstract string ID { get; set; }
public abstract string Name{ get; set; }
}
public class DerivedClassOne : TestCaseData
{
public override string ID
{
get { return id; }
set
{
if ( ... ) throw new ArgumentException();
...
id = value;
}
}
...
}
This way an exception is thrown as soon as an invalid value is encountered. Imagine if you created a million of these objects before checking if each one was valid, only to find that the very first one was invalid. This solution avoids a situation like that by proactively validating as the properties are set.
In the below example, I'm just trying to get Test_Person_Name.FirstName to map to something (anything) in TestPersonFlattened. At this point, considering the amount of time I've sunk into this, I'm not too hung up on what the destination property name is..I just want it to work.
public class Test_Person
{
public Test_Person_Name Test_Person_PublicName { get; set; }
}
public class Test_Person_Name
{
public string FirstName { get; set; }
public string LastName { get; set; }
}
public class TestPersonFlattened
{
public string Test_Person_PublicNameFirstName { get; set; } // What do I call this property?
}
AutoMapper.Mapper.CreateMap<Test_Person, TestPersonFlattened>();
AutoMapper.Mapper.AssertConfigurationIsValid();
It seems like Test_Person_PublicNameFirstName should work, but I get an exception on AssertConfigurationIsValid(). I've also tried TestPersonPublicNameFirstName, Test_Person_PublicName_FirstName as destination property names.
It'd be unfavorable to rename the source property name, just because the source library is used in many other projects. Also, a ForMember() call isn't ideal, but I'll do it if there's no other option.
One way to do it would be to simply leave out "Test_Person_" from the PublicNameFirstName property of your TestPersonFlattened class, and use RecognizePrefixes() to make it so that AutoMapper ignores "Test_Person_" when attempting to map property names.
The following code succeeds:
public partial class App : Application
{
public App()
{
Mapper.Initialize(cfg =>
{
cfg.RecognizePrefixes("Test_Person_");
cfg.CreateMap<Test_Person, TestPersonFlattened>();
});
Mapper.CreateMap<Test_Person, TestPersonFlattened>();
Mapper.AssertConfigurationIsValid();
}
}
public class Test_Person
{
public Test_Person_Name Test_Person_PublicName { get; set; }
}
public class Test_Person_Name
{
public string FirstName { get; set; }
public string LastName { get; set; }
}
public class TestPersonFlattened
{
public string PublicNameFirstName { get; set; } // This is what I call this property!
}
I have ASP.NET MVC 3 application with the following class:
public class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
public Address HomeAddress { get; set; }
// [Optional("MailingAddrressSameAsHome")] - some custom attribute
public Address MailingAddress { get; set; }
public bool MailingAddrressSameAsHome { get; set; }
}
public class Address
{
[Required]
public string Street { get; set; }
...
}
And now I would like to validate, mailing address only when MailingAddressSameAsHome is false. Unfortunatelly I don't known how to stop validating properties in Address class.
Do you have any ideas?
Did you consider only setting MailingAddress when needed, thus letting the property MailingAddrressSameAsHome be read-only:
public bool MailingAddrressSameAsHome
{
//Null means no MailingAddress, which means: use HomeAddress
get { return MailingAddress == null ; }
}
If so, you can validate MailingAddress whenever present.
Regards,
Morten
You could write this with a custom attribute