CODEWITHSUNDEEP
c#entity-frameworkgenericsreflection
Satyajit
Satyajit

Reputation: 2071

Reflection on IQueryable OfType<>

I have a Employees DbSet in my Entity Framework context that can be queried as:

IQueryable employees = _context.Employees;

The Idea is to execute the below method using Reflection:

var result= _context.Employees.OfType<PaidEmployee>()

I have extended the Employee object to create an PaidEmployee class. I want to query the context for PaidEmployee using REFLECTION.

Assembly asm = Assembly.LoadFrom("MyModel.dll");
Type t = asm.GetType("PaidEmployee");

var ofType = typeof(Queryable).GetMethod("OfType",
                     BindingFlags.Static | BindingFlags.Public);

var methodinfo = ofType.MakeGenericMethod(t);

var obj = methodinfo.Invoke(employees , null);

When I execute the above code, it gives me the error:

System.Reflection.TargetParameterCountException was unhandled by user code HResult=-2147352562 Message=Parameter count mismatch.
Source=mscorlib StackTrace: at System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters) at Tests.test_dynamic.TestMethod2() in e:\Projects\Tests\test_dynamic.cs:line 54 InnerException:

Upvotes: 2

Views: 892

Answers (1)

xanatos
xanatos

Reputation: 111860

Try

var obj = methodinfo.Invoke(null, new[] { employees });

The OfType is static, so null obj (the first parameter of Invoke, that is the instance of the object to use for the method)!

Upvotes: 3

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