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C# - How to join data from two generic types together

Is it possible to join two types together (like doing .AddRange in a list) using for example reflection?
Something like in this reponse https://stackoverflow.com/a/8702650/13112059, but here the data from the target object gets replaced.
public class ItemsResponse
{
public List<Items> Items{ get; set; } = new List<Items>();
}
In my case I receive a response from an API and cast the data to this type for example which is only defined at runtime, but then I also need to do another request where I receive data from the same type and I wanted to join this objects together to return them as one.
Example of a request:
public static async Task<T> Query()
{
var response = new T();
var response2 = new T();
response = (T)await RequestAsync(); // First request
/// ...
response2 = (T)await RequestAsync(); // Second request
// I want to return an object containing data from the two responses
}
Thanks!

A generic type parameter, i.e. <T> is not a runtime type. The type is still statically known, just not by this particular piece of code. Sooner or later you have to supply an actual type for your T, this might be done in some third party code, but it will still be known at compile time. Ofc, it might be defined at runtime, but that is not really relevant here.
If you want to create a list of responses you just need to include the generic type parameter in any classes or methods that handles these types.
public static List<T> MakeRequests<T>(MyRequestObject obj){
var items = new List<T>();
items.Add(obj.Query());
// Do more queries, or whatever else you want
return items;
}
You cannot really use the returned objects from your query, other than putting them in a collection, or converting them to string or object. So generic code like this is typically limited to fairly simple things that needs to be done regardless of the actual type.
Collections may include things like tuples, i.e. (T Request1, T Request2), but you cannot combine two object into an object of the same type, at least not without a horrible amount of reflection.

Is there a way to make a IEnumerable method that lets me return any list type in c#?

So currently, you can imagine I have 1 method that is the constructor that funcitons like
info.PersonalInfo=getPersonalInfo(Id);
info.MedicalInfo=getMedicalInfo(Id);
Thing is, all of those get data and get binarys are repeating 95% of the code
using (CVDataEntities data = new CVDataEntities())
{
var temp = data.PersonalInfo.Where(m => m.Id == Id).FirstOrDefault();
return temp;
}
The only thing that changes is instead of PersonalInfo its MedicalInfo.
I thought of using a switch and just sending a number as the selector for which specific object I would want.
But the problem is the method is made so that it can only return
public IEnumerable<PersonalInfo> getPersonalInfo (string Id)
Is there any way for me to make a IEnumerable that lets me return any object, or is there a better way to go about this. I want to do it mostly to reduce the code from 400 lines down to 200 at most.

Try using generic methods, you will be able to specify the return type of your function when you call it. This could make your code look like this :
public IEnumerable<T> getInfo<T>(string id)
{
// Some code
}
// Calling the function
info.PersonalInfo = getInfo<PersonalInfo>(Id);
info.MedicalInfo = getInfo<MedicalInfo>(Id);
But be careful while using it, cause the compiler won't know what type T is (it is only defined at runtime) so it could lead to some errors while processing the data (like missing properties / methods exclusive to a specific type)
EDIT : Johnathan Barclay made a good point by commenting that the // some code bit is relevant and asked "How would the correct property be selected on data? How do you access an Id property on T?"
To get the correct property and access an Id property, you could use System.Reflection and add a string parameter to get the name of the property you want to use, and another to give the Id property name to the function:
public IEnumerable<T> getInfo<T>(string id, string propertyToReadName, string propertyToCompareName)
{
using (CVDataEntities data = new CVDataEntities())
{
// Getting the enumerable not filtered first
IEnumerable<T> unfilteredList = (IEnumerable<T>)data.GetType() // Get the type
.GetProperty(propertyToReadName, typeof(T)) // Get the property (PersonalInfo or MedicalInfo)
.GetValue(data); // Get the value of this property in the `data` instance
// Filtering the list
IEnumerable<T> filteredList = unfilteredList.Where(m =>
typeof(T).GetProperty(propertyToCompareName) // Get the "id" property using parameter
.GetValue(m) // Get the "id" value of m instance
.Equals(id)); // Check if it equals the id given as parameter
return filteredList;
}
}
// Calling the function
info.PersonalInfo = getInfo<PersonalInfo>(Id, "PersonalInfo", "Id");
info.MedicalInfo = getInfo<MedicalInfo>(Id, "MedicalInfo", "Id");
If you want to return a single element instead of an IEnumerable don't forget to change the return type of the function from IEnumerable<T> to T and add .FirstOrDefault() at the return line
Note that you could also give another value to the parameter propertyToCompareName and make a comparison to another property of the T class

Dynamically get a DbSet<T> by Entity class name

I'm trying to use System.Reflections to get a DbSet<T> dynamically from its name.
What I've got right now is:
The DbSet name
The DbSet's Type stored on a variable
The issue I'm facing comes out when trying to use the dbcontext.Set<T>() method, since (these are my tries so far):
When I try to assign to <T> my DbSet Type, it throws me the following compilation error:
"XXX is a variable but is used like a type"
If I try with using both the Extension methods that you will find below in my code (which I made in order to try to get an IQueryable<T>), it returns a IQueryable<object>, which unfortunately is not what I am looking for, since of course when I try to manipulate it with further Reflections, it lacks of all the properties that the original class has…
What am I doing wrong? How can I get a DbSet<T>?
My code is the following, but of course, let me know if you need more infos, clarifications or code snippets.
My Controller's Method:
public bool MyMethod (string t, int id, string jsonupdate)
{
string _tableName = t;
Type _type = TypeFinder.FindType(_tableName); //returns the correct type
//FIRST TRY
//throws error: "_type is a variable but is used like a type"
var tableSet = _context.Set<_type>();
//SECOND TRY
//returns me an IQueryable<object>, I need an IQueryable<MyType>
var tableSet2 = _context.Set(_type);
//THIRD TRY
//always returns me am IQueryable<object>, I need an IQueryable<MyType>
var calcInstance = Activator.CreateInstance(_type);
var _tableSet3 = _context.Set2(calcInstance);
//...
}
Class ContextSetExtension
public static class ContextSetExtension
{
public static IQueryable<object> Set(this DbContext _context, Type t)
{
var res= _context.GetType().GetMethod("Set").MakeGenericMethod(t).Invoke(_context, null);
return (IQueryable<object>)res;
}
public static IQueryable<T>Set2<T>(this DbContext _context, T t)
{
var typo = t.GetType();
return (IQueryable<T>)_context.GetType().GetMethod("Set").MakeGenericMethod(typo).Invoke(_context, null);
}
}
EDIT Added TypeFinder's inner code.
In brief, this method does the same of Type.GetType, but searches Type on ALL the generated assemblies
public class TypeFinder
{
public TypeFinder()
{
}
public static Type FindType(string name)
{
Assembly[] assemblies = AppDomain.CurrentDomain.GetAssemblies();
var result = (from elem in (from app in assemblies
select (from tip in app.GetTypes()
where tip.Name == name.Trim()
select tip).FirstOrDefault())
where elem != null
select elem).FirstOrDefault();
return result;
}
}
UPDATE as requested in the comments, here's the specific case:
In my DB i've got some tables which are really similar each other, so the idea was to create a dynamic table-update method which would be good for every table, just passing to this method the table name, the ID of the row to update and the JSON containing data to update.
So, in brief, I would perform some updates on the table given in input as DbSet type, updating the row with ID==id in input with the data contained inside the JSON, which will be parsed inside an object of type X(the same of dbset)/into a dictionary.
In pseudo-code:
public bool MyMethod (string t, int id, string jsonupdate)
{
string _tableName = t;
Type _type = TypeFinder.FindType(_tableName); //returns the correct type
//THIS DOESN'T WORKS, of course, since as said above:
//<<throws error: "_type is a variable but is used like a type">>
var tableSet = _context.Set<_type>();
//parsing the JSON
var newObj = Newtonsoft.Json.JsonConvert.DeserializeObject(jsonupdate, _type);
//THIS OF COURSE DOESN'T WORKS TOO
//selecting the row to update:
var toUpdate = tableSet.Where(x => x.Id == id).FirstOrDefault();
if(toUpdate!=null)
{
var newProperties = newObj.GetType().GetProperties();
var toUpdateProperties = toUpdate.GetType().GetProperties();
foreach(var item in properties)
{
var temp = toUpdateProperties.Where(p => p.Name==item.Name)
{
//I write it really in briefand fast, without lots of checks.
//I think this is enough, I hope
temp.SetValue(toUpdate, item.GetValue());
}
}
_context.SaveChanges();
}
return false;
}

returns me an IQueryable<object>, I need an IQueryable<MyType>
Well, that will never work. Your IQueryable cannot be of type IQueryable<MyType>because that would mean the compiler would need to know what MyType is and that is not possible, because the whole point of this exercise is to decide that on runtime.
Maybe it's enough to know that those objects are in fact instances of MyType?
If not, I think you have painted yourself into a corner here and you are trying to figure out what paint to use to get out of there. Take a step back, it's probably not a technical problem. Why do you need to do this? Why do you have the conflicting needs of knowing the type at runtime only and knowing it at compile time?
You need to think about your requirements, not about the technical details.

I needed to dynamically load a single record from the database for each type in a list of known types, to print a test email when an admin is editing the template, so I did this:
List<object> args = new List<object>();
//...
//other stuff happens that isn't relevant to the OP, including adding a couple fixed items to args
//...
foreach (Type type in EmailSender.GetParameterTypes())
{
//skip anything already in the list
if (args.Any(a => a.GetType().IsAssignableFrom(type))) continue;
//dynamically get an item from the database for this type, safely assume that 1st column is the PK
string sql = dbContext.Set(type).Sql.Replace("SELECT", "SELECT TOP 1") + " ORDER BY 1 DESC";
var biff = dbContext.Set(type).SqlQuery(sql).AsNoTracking().ToListAsync().Result.First();
args.Add(biff);
}
Caveat: I know at least one record will exist for all entities I'm doing this for, and only one instance of each type may be passed to the email generator (which has a number of Debug.Asserts to test validity of implementation).
If you know the record ID you're looking for, rather than the entire table, you can use dbContext.Set(type).Find(). If you want the entire table of whatever type you've sussed out, you can just do this:
string sql = dbContext.Set(type).Sql; //append a WHERE clause here if needed/feasible, use reflection?
var biff = dbContext.Set(type).SqlQuery(sql).ToListAsync().Result;
Feels a little clunky, but it works. There is strangely no ToList without Async, but I can run synchronously here. In my case, it was essential to turn off Proxy Creation, but you look like you want to maintain a contextful state so you can write back to db. I'm doing a bunch of reflection later, so I don't really care about strong typing such a resulting collection (hence a List<object>). But once you have the collection (even just as object), you should be able to use System.Reflection as you are doing in your UPDATE sample code, since you know the type and can use SetValue with known/given property names in such a manner.
And I'm using .NET Framework, but hopefully this may translate over to .NET Core.

EDIT: tested and working:
public async Task<bool> MyMethod(string _type)
{
Type type = Type.GetType(_type);
var tableSet = _context.Set(type);
var list = await db.ToListAsync();
// do something
}
// pass the full namespace of class
var result = await MyMethod("Namespace.Models.MyClass")
IMPORTANT NOTE: your DbContext need to have the DbSet declared to work!
public class MyContext : DbContext
{
public DbSet<MyClass> MyClasses { get; set; }
}

C#, Generics, Type and NHibernate

I'm learning the power of generics in C# in conjunction with NHibernate. I'd like to attempt the following in the pasted code.
In an attempt to do some post processing of N number of NHibernate objects I worked on a utility method leveraging generics to make it applicable to all NHibernate mapping classes we use now, or in the future. It works but I need to hard code each call for each mapping class. This is a pain and will need continuing updating as our schema and mappings change over time.
I do have an ever up-to-date list of all mapping classes by string name through the NHibernate mappings I generate on the fly. If there was a way to use this list of string names to call my generics based method, I'd be super happy.
Can anyone tell me if this is possible? Do I need to find another route?
Thanks so much in advance!!!
public static void ProcessSomeItems()
{
// *************************************************************
// As of now I have to list all classes as such to be processed
// It works but I have to update manually when new mapping classes are created
// *************************************************************
NHibDoSomethingUtil<AspnetMembership>();
NHibDoSomethingUtil<AspnetProfile>();
NHibDoSomethingUtil<AspnetRole>();
NHibDoSomethingUtil<AspnetUser>();
// and so forth...
// I have a up-to-date list of all mappings from "HbmMapping" and can get a list of all in the
// list form as below
List<string> mappingNames = new List<string>();
foreach (string mappingName in mappingNames)
{
Type theType = Type.GetType(mappingName);
// I know I'm getting Types and Generics classes and so forth all jumbled but
// how in the heck would I do something like the below?
NHibDoSomethingUtil<theType>(); // Obviously doesn't compile ;-)
}
}
// Generic method
public static void NHibDoSomethingUtil<T>() where T : class
{
using (ISession session = sourceDBSessionFactory.OpenSession())
{
foreach (dynamic item in new List<T>(session.QueryOver<T>().List()))
{
// Process item;
}
}
}
ecsousa gave great input and I was able to accomplish what I needed with something like the following.
foreach (HbmClass mappingClass in mapping.Items)
{
Console.WriteLine(" -- Discovered Mapping: " + mappingClass.Name);
Type mappingClassType = Type.GetType(mappingClass.Name);
var genericMethod = typeof(Migration).GetMethod("NHibDoSomethingUtil");
var method = genericMethod.MakeGenericMethod(mappingClassType);
method.Invoke(null, null);
}

You will need to use Reflection in order to accomplish this. Instead of directly calling NHibDoSomethingUtil, try this:
var genericMethod = typeof(TheClassName).GetMethod("NHibDoSomethingUtil");
var method = genericMethod.MakeGenericMethod(theType);
method.Invoke(null, null);
Note that you have to replace TheClassName by the class containing both methods.
Keep in mind the this kind of code is slow, and you should use it very carefully.

Calling custom (formatting) method on LINQ to Entities

I'm using EF 4.1 and I'm trying to enumerate a company list for a grid. I have two options in the current project: select all companies from the DbContext (Entities) and load them into an object from a non-anonymous type (let's say EmpresaGrid) or select all companies into anonymous type objects with the same structure like Empresa (which is the entity I'm selecting from).
The first option (creating a model class for that) would require a little more work, but can be, eventually, more readable. Still, I'm not sure about that. The second option is what I'm using right now.
So, first question: it's better to create a model class only for displaying data or use anonymous type? Doing a direct select is out of question: a SELECT * is too big and that might make everything damn slow (I guess). So selection into another type creates a custom query with only the needed fields.
Using the second option (anonymous type), I have this code (simplified version):
public static IEnumerable<object> Grid()
{
Entities db = new Entities();
var empresas = db.Empresas
.Select(e => new
{
Cgc = e.Cgc, // PK
(...)
Address = new
{
AddressLine = e.EnderecoSede.AddressLine,
(...)
}
},
Contato = e.Contato,
(...)
})
.ToList();
return empresas;
}
The anonymous type I'm creating has around 40 lines of code, so it's kinda big, but it recreates part of the Empresa class struct (since the grid is waiting for a Empresa object). Anyway, I have a problem with the data format. For example, I would like to format the Cgc property using a custom string format. I have a public method for this, FormataCgc. This method receives a string and returns it formatted using some internal conditions.
So, my problem is how to that. For example, I have tried this:
var empresas = db.Empresas
.Select(e => new
{
Cgc = FormataCgc(e.Cgc),
}
But that doesn't work because FormataCgc cannot be translated into SQL (and I don't want to convert it). I also tried this:
var empresas = db.Empresas
.Select(e => new
{
(...)
}
.ToList();
foreach (var e in empresas) {
e.Cgc = FormataCgc(e.Cgc);
}
But it cannot be done since anonymous types have only read-only properties.
So, my second question is: how exactly can I do that? I need to change the data after selecting it, but using anonymous types? I've done a little research, and the best thing I've found was this: Calling a custom method in LINQ query. In that solution, Ladislav suggested doing a second select from the IEnumerable, but since the grid is excepting Empresa I cannot do that (I need to change or add properties, not encapsulate them).
I'm not sure if I was clear enough, but feel free to ask any questions. Also, the grid I'm currently using is a Telerik ASP.NET MVC Grid, which receives a IEnumerable (where T is a class) as model data and them iterates each object, doing its magic.

Since you're already converting this into an IEnumerable<T>, you can do the custom formatting as you stream the results in the client. Do your db.Select, and then convert to the appropriate format afterwards, ie:
var empresas = db.Empresas
.Select(e => new
{
(...)
})
.ToList();
foreach (var e in empresas) {
yield return new {
Cgc = FormataCgc(e.Cgc),
// Copy other properties here, as needed...
};
}
That being said, I'd personally recommend making a custom class, and not return an anonymous type. Your conversion would then be:
foreach (var e in empresas) {
yield return new YourClass(FormataCgc(e.Cgc), ...); // Construct as needed
}
This will dramatically improve the usability of this method, as you will have proper, named access to your properties from the caller of the method.

I think the solution to both of your questions is to create a model class. Sure it is a little bit more work up front, but it will allow you greater flexibility in the long run. Your custom model class can then handle the formatting for you.
public class EmpresaGridModel
{
public string Cgc { get; set; }
public string CgcFormatted
{
return FormataCgc(this.Cgc);
}
//properties for the other fields will have to be created as well obviously
}
Your telerik grid can then bind directly to the CgcFormatted property