Missing a cast in a linq query for a controller - c#

I am new with c# controllers and I am trying to join two entities with a LINQ query. But I am getting a 'missing a cast' error message as shown below that I don't understand and it does not help me to correct the error.
The controller looks like:
public class SoonDueReportsController_simple : BaseODataController
{
public SoonDueReportsController_simple(IUnitOfWork unitOfWork)
{
UnitOfWork = unitOfWork;
}
[Queryable(AllowedQueryOptions = AllowedQueryOptions.All)]
public SoonDueReportsController_simple Get()
{
var falligkeiten = UnitOfWork.GetAll<Fälligkeiten>();
var betriebe = UnitOfWork.GetAll<Betriebe>();
var query = (from betrieb in betriebe.AsQueryable()
join fallig in falligkeiten.AsQueryable()
on betrieb.ID equals
fallig.Betrieb_ID
where fallig.Fälligkeit_Erledigt_Datum == null
&& betrieb.Aktiv == true
select new
{
BetriebId = betrieb.ID,
FalligkeitObject = fallig.Fälligkeit_Objekt
});
return query;
}
}
This type of controller I have used with success for single entities (tables from an sql db) to display static data in a kendo grid. But I fail when I try to join two tables as shown above. If someone could help me with this problem I'd appreciate it very much.
Regards, Manu

You select a collection of anonymous objects
select new
{
BetriebId = betrieb.ID,
FalligkeitObject = fallig.Fälligkeit_Objekt
});
And want the method to return a instance of certain type. C# is the strongly typed language without type inference, which means you have to specifically create objects of a certain type or interface if you want to return them.
Also, you are have the controller type itself to be returned from the Get method. This makes no sense. I actually do not know what you want to do but may be this would work:
public class SoonDueReportsController_simple : BaseODataController
{
public SoonDueReportsController_simple(IUnitOfWork unitOfWork)
{
UnitOfWork = unitOfWork;
}
[Queryable(AllowedQueryOptions = AllowedQueryOptions.All)]
public IQueryable<SomeModel> Get()
{
var falligkeiten = UnitOfWork.GetAll<Fälligkeiten>();
var betriebe = UnitOfWork.GetAll<Betriebe>();
var query = (from betrieb in betriebe.AsQueryable()
join fallig in falligkeiten.AsQueryable()
on betrieb.ID equals
fallig.Betrieb_ID
where fallig.Fälligkeit_Erledigt_Datum == null
&& betrieb.Aktiv == true
select new SomeModel
{
BetriebId = betrieb.ID,
FalligkeitObject = fallig.Fälligkeit_Objekt
});
return query;
}
}
public class SomeModel
{
public int BetriebId { get; set; }
public string FalligkeitObject { get; set; }
}
Please bear in mind that there are no such things as "C# controllers". You are working with OData, so I would recommend you to look at some OData resources, there are plenty of examples out there.
And one last thing, don't get me wrong, but it does not help giving properties, types and other identifiers German names. People would have hard time trying to understand your code.

The exception explains to you the problem exactly. You're wanting to return a type of 'SoonDueReportsController_simple' and yet you are returning a Queryable where a' is your new { ..., ... } object.
I like the suggestion given to make a strong typed object and fill it but you can also return a dynamic type.
This code works to explain:
private dynamic Get() => new { Name = "SomeName", Age = 31 };
private void TestGet()
{
var obj = Get();
var name = obj.Name;
var age = obj.Age;
}

Related

Convert EF6 to EF core with the ObjectResult

I have some code I am trying to convert. I don't have these ObjectResult and ObjectContext anymore
This is what I did have:
public virtual ObjectResult<string> GetTransData(string iN_MEM_ID)
{
var iN_MEM_IDParameter = iN_MEM_ID != null ?
new ObjectParameter("IN_MEM_ID", iN_MEM_ID) :
new ObjectParameter("IN_MEM_ID", typeof(string));
return ((IObjectContextAdapter)this).ObjectContext.ExecuteFunction<string>("GetTransData", iN_MEM_IDParameter);
}
Since I need a List to be returned from a caller ( it is sent back as json data )
This is what I am trying to build
public virtual List<string> GetTransData(string iN_MEM_ID)
{
var iN_MEM_IDParameter = iN_MEM_ID != null ?
new SqlParameter("IN_MEM_ID", iN_MEM_ID) :
new SqlParameter("IN_MEM_ID", typeof(string));
Clinical_CaseTrakker_Context clinical = new Clinical_CaseTrakker_Context();
List<string> offLine = clinical.string.FromSql("EXECUTE CT.GetTransData {0}", iN_MEM_IDParameter);
return offLine;
}
Notice that I am stuck with clinical.string i can't do that , but I am not sure how to take dbcontext instance and run FromSql to execute sql and return to List
In EF Core, it is not possible to use the FromSql method to return a subset of properties (a projection) directly from the database.
You are required to define a some model and a DbSet for that class
public class Foo
{
public string Bar { get; set; }
}
then declare in your context
public DbSet<Foo> Foos { get; set; }
and use it like:
using (var context = new Clinical_CaseTrakker_Context())
{
var offLine = context.Foos
.FromSql($"EXECUTE CT.GetTransData {iN_MEM_IDParameter}")
.Select(x => x.Bar)
.ToList();
return offLine;
}
Your Context needs a virtual DbSet<string> ResultStrings { get; set; } that you can call upon and put the result in. (This does not work, see this post or Roman Marusyk comment below)
EDIT: Your Context needs a virtual DbSet<ResultEntity> ResultEntities { get; set; } that you can call upon and put the result in.
Then you can do return clinical.ResultEntities.FromSql("EXECUTE CT.GetTransData {0}", iN_MEM_IDParameter").toList() to fill the set.
Considering the ResultEntity has an Id and a value property, you can do ResultEntities.Select(e => e.value).toList() to extract a list of strings from the set.

How do I solve the Razor Pages error "CS0103 The name 'Json' does not exist in the current context"?

I am using Razor Pages (not MVC) and keep getting the above error on the return statement. There is a similar question out there relating to the MVC model but the answer to that one is to change the class to "Controller". When I try that, page related things break. Any suggestions?
public class VehicleInfoPageModel : PageModel
{
public SelectList ModelNameSL { get; set; }
public JsonResult PopulateModelDropDownList(StockBook.Models.StockBookContext _context,
int selectedMakeID,
object selectedModelID = null)
{
var ModelIDsQuery = from m in _context.VehicleModel
orderby m.ModelID // Sort by ID.
where m.MakeID == selectedMakeID
select m;
ModelNameSL = new SelectList(ModelIDsQuery.AsNoTracking(),
"ModelID", "ModelName", selectedModelID);
return Json(ModelNameSL);
}
You're tried to use Json() method which derived from either System.Web.Mvc.JsonResult or System.Web.Http.ApiController.JsonResult instead of Microsoft.AspNetCore.Mvc.JsonResult namespace, they're all different namespaces. You should use the constructor of Microsoft.AspNetCore.Mvc.JsonResult to create JSON string instead:
public JsonResult PopulateModelDropDownList(StockBook.Models.StockBookContext _context, int selectedMakeID, object selectedModelID = null)
{
var ModelIDsQuery = from m in _context.VehicleModel
orderby m.ModelID // Sort by ID.
where m.MakeID == selectedMakeID
select m;
ModelNameSL = new SelectList(ModelIDsQuery.AsNoTracking(),
"ModelID", "ModelName", selectedModelID);
// return JSON string
return new JsonResult(ModelNameSL);
}
Reference: Working With JSON in Razor Pages

Pass linq query result to viewmodel

In my MVC web application, I have linq query that feth the record from database, I want to display that record on view using viewmodel. I have tried with following code.
[HttpGet]
public ActionResult CreatePDF()
{
RentalAgreementEntities db = new RentalAgreementEntities();
String strSession1 = "39726-10275-6027589725",strStatus = "Y",strUserType = "L";
var q = (from um in db.User_Master
join ut in db.UserType_Master on um.US_SerialNo.ToString() equals ut.UT_UserNo
join pu in db.PropertyUser_Master on ut.UT_SerialNo.ToString() equals pu.PU_UserNo
join pr in db.Property_Master on pu.PU_PropertyNo equals pr.PR_SerialNo.ToString()
where pr.PR_MakerID == strSession1
&& ut.UT_Status == strStatus
&& ut.UT_UserType == strUserType
select new
{
um.US_FirstName,
um.US_LastName
}
).AsEnumerable().Select(um => new User_Master {
US_FirstName = um.US_FirstName.ToString(),
US_LastName=um.US_LastName
}).ToList();
var myviewmodel=new viewmodelPDF()
{
lsusermaster=q.ToList();
}
return View("pdfgenerationvw",myviewmodel);
}
I also created viemodel to manage all model's for to display on a view (Here, Just one model access code).
public class viewmodelPDF
{
public List<User_Master> lsusermaster { get; set; }
}
My model class, for which I am going to fetch record from database.
public partial class User_Master
{
public string US_FirstName { get; set; }
public string US_LastName { get; set; }
public int US_SerialNo { get; set; }
}
//Other Models
Now my problem is that, In my action code , when I am trying to assign query result to the lsusermaster of viewmodel then it gives compiler error as belows.
I don't know, why this compile error is thrown, How can I assign query result to viemodel property?
Try this:
var myviewmodel=new viewmodelPDF()
{
lsusermaster=q.ToList()
};
When you are using an object initializer in C#, you can't use ; between the properties, you use it at the end of the initializer
So just remove the ; (or use a ,, as suggested), and move it to the end of the initializer block
var myviewmodel=new viewmodelPDF()
{
lsusermaster=q.ToList()
};
Using a , works even if there are no more properties... it "looks" bad, but it makes easier to add new properties should you ever need them... if the code is final, I'd not use it, but that's personal preference

Find a generic DbSet in a DbContext dynamically

I know this question has already been asked but I couldn't find an answer that satisfied me. What I am trying to do is to retrieve a particular DbSet<T> based on its type's name.
I have the following :
[assembly: System.Runtime.CompilerServices.InternalsVisibleTo("MyDllAssemblyName")]
[assembly: System.Runtime.CompilerServices.InternalsVisibleTo("MyCallingAssemblyName")]
class MyDbContext : DbContext {
public DbSet<ModelA> A { get; set; }
public DbSet<ModelB> B { get; set; }
public dynamic GetByName_SwitchTest(string name) {
switch (name) {
case "A": return A;
case "B": return B;
}
}
public dynamic GetByName_ReflectionTest(string fullname)
{
Type targetType = Type.GetType(fullname);
var model = GetType()
.GetRuntimeProperties()
.Where(o =>
o.PropertyType.IsGenericType &&
o.PropertyType.GetGenericTypeDefinition() == typeof(DbSet<>) &&
o.PropertyType.GenericTypeArguments.Contains(targetType))
.FirstOrDefault();
if (null != model)
return model.GetValue(this);
return null;
}
}
I have no trouble getting the type itself whether it is via a simple switch or reflection. I need however to return the type as a dynamic since I do not know what DbSet type it will be.
Then somewhere else in the same assembly, I use it this way :
// MyDbContext MyDbContextInstance..
var model = MyDbContextInstance.GetByName_SwitchTest("A");
var record1 = model.FirstOrDefault(); // It crashes here with RunTimeBinderException
At this point model contains an instance of a InternalDbSet<ModelA> type. From there, any use I do with the model object I get a RunTimeBinderException :
'Microsoft.Data.Entity.Internal.InternalDbSet' does not contain a definition for 'FirstOrDefault'
Investigating on the web, I found a blog post explaining that (dixit his blog) :
the reason the call to FirstOrDefault() fails is that the type
information of model is not available at runtime. The reason it's not
available is because anonymous types are not public. When the method
is returning an instance of that anonymous type, it's returning a
System.Object which references an instance of an anonymous type - a
type whose info isn't available to the main program.
And then he points that a solution :
The solution is actually quite simple. All we have to do is open up
AssemplyInfo.cs of the ClassLibrary1 project and add the following
line to it: [assembly:InternalsVisibleTo("assembly-name")]
I did try this solution on my code but it doesn't work. For info I have an asp.net 5 solution with two assemblies running on dnx dotnet46. An app and a dll containing all my models and DbContext. All the concerned calls I do are located on the dll though.
Does this solution have any chance to work ?
Am I missing something ?
Any pointers would be greatly appreciated ?
Thanks in advance
[EDIT]
I have tried to return IQueryable<dynamic> rather than dynamic and I could do the basic query model.FirstOrDefault(); but above all I'd like to be able to filter on a field too :
var record = model.FirstOrDefault(item => item.MyProperty == true);
So how did I do it when I am not aware of <T> during compile time.
First need to get the type as DbContext.Set method returns a non-generic DbSet instance for access to entities of the given type in the context and the underlying store.
public virtual DbSet Set(Type entityType)
Note here argument is the type of entity for which a set should be returned.And set for the given entity type is the return value.
var type = Assembly.GetExecutingAssembly().GetTypes().FirstOrDefault(t => t.Name == <Pass your table name>);
now once I have this type
if(type != null)
{
DbSet context = context.Set(type);
}
Or a one liner would be
DbSet mySet = context.Set(Type.GetType("<Your Entity Name>"));
*Disclaimer: This response doesn't give a stricto sensu answer to my question. It is rather a different approach to resolve my own problem. I am aware this is a specific example for a given situation that will not work for everyone. I am posting this approach in the hope it helps someone but will not mark it as the answer as I am still hoping for a real solution.
To start with, let's accept the fact that the only useful information we can get out of the current code is whether a record exists or not.. Any attempt of a dynamic queries after that would give the RuntimeBinderException.
Then let's continue with another fact; DbContext.Add(object) and DbContext.Update(object) are not template based so we can use them to save our models ( Instead of db.A.Add() or db.A.Update() )
In my own situation, no more is required to work out a procedure
Define models a little differently
To start with, I need a field that is retrievable across all my models which should obviously be a way to identify a unique record.
// IModel give me a reliable common field to all my models ( Fits my DB design maybe not yours though )
interface IModel { Guid Id { get; set; } }
// ModelA inherit IModel so that I always have access to an 'Id'
class ModelA : IModel {
public Guid Id { get; set; }
public int OtherField { get; set; }
}
// ModelB inherit IModel so that I always have access to an 'Id'
class ModelB : IModel {
public Guid Id { get; set; }
public string WhateverOtherField { get; set; }
}
Re-purpose the dynamic queries a bit to do something we know works
I haven't found a way to do smart query dynamically, so instead I know I can reliably identify a record and know if it exists or not.
class MyDbContext : DbContext {
public DbSet<ModelA> A { get; set; }
public DbSet<ModelB> B { get; set; }
// In my case, this method help me to know the next action I need to do
// The switch/case option is not pretty but might have better performance
// than Reflection. Anyhow, this is one's choice.
public bool HasRecord_SwitchTest(string name) {
switch (name) {
case "A": return A.AsNoTracking().Any(o => o.Id == id);
case "B": return B.AsNoTracking().Any(o => o.Id == id);
}
return false;
}
// In my case, this method help me to know the next action I need to do
public bool HasRecord_ReflectionTest(string fullname)
{
Type targetType = Type.GetType(fullname);
var model = GetType()
.GetRuntimeProperties()
.Where(o =>
o.PropertyType.IsGenericType &&
o.PropertyType.GetGenericTypeDefinition() == typeof(DbSet<>) &&
o.PropertyType.GenericTypeArguments.Contains(targetType))
.FirstOrDefault();
if (null != model)
return (bool)model.GetValue(this).AsNoTracking().Any(o => o.Id == id);
return false;
}
// Update and save immediately - simplified for example
public async Task<bool> UpdateDynamic(object content)
{
EntityEntry entry = Update(content, GraphBehavior.SingleObject);
return 1 == await SaveChangesAsync(true);
}
// Insert and save immediately - simplified for example
public async Task<bool> InsertDynamic(object content)
{
EntityEntry entry = Add(content, GraphBehavior.SingleObject);
return 1 == await SaveChangesAsync(true);
}
}
A little bit of plumbing to give a sense to my situation
Next, what I needed to do with that dynamic queries was a way to replicate data from a server down to my client. ( I have omitted a big chunk of the architecture to simplify this example )
class ReplicationItem
{
public ReplicationAction Action { get; set; } // = Create, Update, Delete
public string ModelName { get; set; } // Model name
public Guid Id { get; set; } // Unique identified across whole platform
}
Connecting the bits.
Now, here's the routine that connects the bits
public async void ProcessReplicationItem(ReplicationItem replicationItem)
{
using (var db = new MyDbContext())
{
// Custom method that attempts to get remote value by Model Name and Id
// This is where I get the strongly typed object
var remoteRecord = await TryGetAsync(replicationItem.ModelName, replicationItem.Id);
bool hasRemoteRecord = remoteRecord.Content != null;
// Get to know if a local copy of this record exists.
bool hasLocalRecord = db.HasRecord_ReflectionTest(replicationItem.ModelName, replicationItem.Id);
// Ensure response is valid whether it is a successful get or error is meaningful ( ie. NotFound )
if (remoteRecord.Success || remoteRecord.ResponseCode == System.Net.HttpStatusCode.NotFound)
{
switch (replicationItem.Action)
{
case ReplicationAction.Create:
{
if (hasRemoteRecord)
{
if (hasLocalRecord)
await db.UpdateDynamic(remoteRecord.Content);
else
await db.InsertDynamic(remoteRecord.Content);
}
// else - Do nothing
break;
}
case ReplicationAction.Update:
[etc...]
}
}
}
}
// Get record from server and with 'response.Content.ReadAsAsync' type it
// already to the appropriately
public static async Task<Response> TryGetAsync(ReplicationItem item)
{
if (string.IsNullOrWhiteSpace(item.ModelName))
{
throw new ArgumentException("Missing a model name", nameof(item));
}
if (item.Id == Guid.Empty)
{
throw new ArgumentException("Missing a primary key", nameof(item));
}
// This black box, just extrapolate a uri based on model name and id
// typically "api/ModelA/{the-guid}"
string uri = GetPathFromMessage(item);
using (var client = new HttpClient())
{
client.BaseAddress = new Uri("http://localhost:12345");
HttpResponseMessage response = await client.GetAsync(uri);
if (response.IsSuccessStatusCode)
{
return new Response()
{
Content = await response.Content.ReadAsAsync(Type.GetType(item.ModelName)),
Success = true,
ResponseCode = response.StatusCode
};
}
else
{
return new Response()
{
Success = false,
ResponseCode = response.StatusCode
};
}
}
}
public class Response
{
public object Content { get; set; }
public bool Success { get; set; }
public HttpStatusCode ResponseCode { get; set; }
}
ps: I am still interested in a real answer, so please keep posting for other answer if you have a real one to share.
You could use this to get the DBSet for a specific type:
public object GetByType(DbContextcontext, Type type) {
var methode = _context.GetType().GetMethod("Set", types: Type.EmptyTypes);
if (methode == null) {
return null;
}
return methode.MakeGenericMethod(type).Invoke(_context, null);
}

How to have a unique C# code with different Entities EF having the same columns

Good morning everybody,
I am doing a AngularJS project using ASP.NET-MVC, C#, EF and an SQL Express DB.
I have an HTML page calling some AngularJS functions calling some functions on MyController.cs.
In MyController.cs I have quite a lot functions using EF.
In my DB, I have hundred of tables with the same columns.
And I want to have the same HTML page for each table, so executing the same functions with different names
For example when I go to the link http://..../Index/TABLE1, MyController.cs would look like :
public ActionResult getCaptions()
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.MaxJsonLength = 500000000;
var data =
_db
.TABLE1
.OrderBy(i => i.CodeId)
.ToArray();
return Content(serializer.Serialize(data).ToString(), "application/json");
}
and when I go to the link http://..../Index/TABLE2, MyController.cs would look like :
public ActionResult getCaptions()
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.MaxJsonLength = 500000000;
var data =
_db
.TABLE2
.OrderBy(i => i.CodeId)
.ToArray();
return Content(serializer.Serialize(data).ToString(), "application/json");
}
I have thought about a solution like this :
Declare a global variable on the controller tableName
Modify the Index ActionResult
public ActionResult Index(string id)
{
tableName = id;
return View();
}
Now I am stuck ...
Any help is needed, thanks.
EDIT : If you downvote, can you at least explain why ? Thanks
I see you #aBennouna may have already given up on this question, but I took an interest in the question and decided it needed a solution. It may not be 100% what you asked for since here you can't take in a table name as a string parameter.
First if all the tables have same columns, you can inherit them from a same base:
public class TableBase
{
[Key]
public int CodeId { get; set; }
public int Prop1 { get; set; }
public int Prop2 { get; set; }
public int Prop3 { get; set; }
}
Using this base we can define our tables:
public class Table1 : TableBase
{
}
public class Table2 : TableBase
{
}
// etc...
This enables us to write a generic GetCaptions method like #CodeCaster suggested (thanks for the nudge in right direction):
public ActionResult GetCaptions<T>() where T : TableBase
{
var set = db.Set<T>();
// get all objects to array
var list = set.OrderBy(i => i.CodeId).ToList();
// serialize and return result
// OR get single object and a value
var item = set.FirstOrDefault();
var propertyValue = item.Prop1;
}
Usage:
GetCaptions<Table1>();
GetCaptions<Table2>();

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