Is it possible to use the DbSet with a generic type?

Question

I've been working on a platform for a rehab center. We need to store the appointments info and each appointment has multiple attendance forms, each attendance form is a table in the database. So, I have the Appointments table and one table for each attendance form. I need to restore the data of a certain appointment and all the attendance forms used in that particular appointment. The problem is that the number of attendance forms varies for each appointment because a healthcare professional can fill different attendance forms according to the appointment.

The name of all attendance forms has the same prefix, so I can do this:

var formsNamesQuery = from table in _context.GetType().GetProperties()
                      where table.Name.StartsWith("Form") 
                      select table.Name;

var formsNames = formsNamesQuery.ToList();

Doing this, now I have only the name of the attendance form tables. To query each table, I do this:

foreach (var formName in formsNames)
{
     var form = _context.GetType().GetProperty(formName).GetType();
     
     var formResults = _context.Set<FormType>().FromSqlRaw(
          $"SELECT * FROM {formName} WHERE PacientID = '{pacientID}' AND AppointmentID = {appointmentID}")
          .AsNoTracking()
          .FirstAsync();
}

But I don't know how to say to the DbContext the type of the form I'm searching for. I've been searching a lot, but I didn't find a solution. I saw this question and it led me to this method:

public IList RestoreFormInfo<TEntity>(TEntity entity, string formName, string pacientID, int AppointmentID) where TEntity : class
{
     var dataSet = _context.Set<TEntity>();

     var results = dataSet.FromSqlRaw(
          $"SELECT * FROM {formName} WHERE PacientID = '{pacientID}' AND AppointmentID = {appointmentID}")
          .AsNoTracking()
          .FirstAsync();
     
     return (IList) results;
}

And I call it like this:

var formResults = RestoreFormInfo(form.GetType(), formName, pacientID, appointmentID);

With this method, I can pass the form type, but I get this error:

InvalidOperationException: Cannot create a DbSet for 'Type' because this type is not included in the model for the context.
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.get_EntityType()
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.CheckState()
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.get_EntityQueryable()
Microsoft.EntityFrameworkCore.Internal.InternalDbSet<TEntity>.System.Linq.IQueryable.get_Provider()
Microsoft.EntityFrameworkCore.RelationalQueryableExtensions.FromSqlRaw<TEntity>(DbSet<TEntity> source, string sql, object[] parameters)
SigCER.Controllers.AppointmentsController.RestoreFormInfo<TEntity>(TEntity entity, string formName, string pacientID, int appointmentID) in AppointmentsController.cs
var results = dataSet.FromSqlRaw(
SigCER.Controllers.AppointmentsController.AttendanceForms(int appointmentID, string pacientID) in AppointmentsController.cs
var formResults = RestoreFormInfo(form.GetType(), formName, pacientID, appointmentID);
lambda_method(Closure , object )
Microsoft.Extensions.Internal.ObjectMethodExecutorAwaitable+Awaiter.GetResult()
Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor+TaskOfActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, object controller, object[] arguments)
System.Threading.Tasks.ValueTask<TResult>.get_Result()
System.Runtime.CompilerServices.ValueTaskAwaiter<TResult>.GetResult()
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask<IActionResult> actionResultValueTask)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|19_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.MigrationsEndPointMiddleware.Invoke(HttpContext context)
Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.Invoke(HttpContext httpContext)
Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.Invoke(HttpContext httpContext)
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Right error message, instead of invoking generic method with appropriate type, you have called this method with Type generic argument. — Svyatoslav Danyliv, May 20 '21 at 17:23
Thank you for helping! I got to call the method with reflection, but the error keeps showing up, now in a slightly different way `Cannot create a DbSet for 'RuntimePropertyInfo'`. It happened previously when trying another solutions to solve this problem. — Renan Oliveira, May 21 '21 at 13:44

score 0 · Accepted Answer · answered May 25 '21 at 16:27

I got to solve the problem like this:

foreach (var formName in formsNames)
{
     var form = typeof(DbContext).GetProperty(formName).PropertyType;
     
     var method = typeof(AppointmentsController).GetMethod("RestoreFormInfo");

     // Because the form variable is a DbSet<FormType>, I needed to get the
     // FormType from the GenericTypeArguments array.
     var genericMethod = method.MakeGenericMethod(form.GenericTypeArguments[0]);

     var formResults = await (Task<object>) genericMethod.Invoke(this, new object[] { formName, pacientID, appointmentID });
}

Now, the RestoreFormInfo method is like this:

public async Task<object> RestoreFormInfo<TEntity>(string formName, string pacientID, int AppointmentID) where TEntity : class
{
     var dataSet = _context.Set<TEntity>();
     
     try
     {
          var results = await dataSet.FromSqlRaw(
               $"SELECT * FROM {formName} WHERE PacientID = '{pacientID}' AND AppointmentID = {appointmentID}")
               .AsNoTracking()
               .FirstAsync();
     }
     catch (InvalidOperationException)
     {
          // The expected error is the "InvalidOperationException: Enumerator failed to MoveNextAsync",
          // it means that the FirstAsync didn't find any result.
          return null;
     }
     
     return results;
}

Is it possible to use the DbSet with a generic type?

1 Answers1