Use variable as Type

Question

Is it possible to make such code work?:

    private List<Type> Models = new List<Type>()
    {
        typeof(LineModel), typeof(LineDirectionModel), typeof(BusStopTimeModel), typeof(BusStopNameModel)
    };

    foreach (Type model in Models) // in code of my method
    {
        Connection.CreateTable<model>(); // error: 'model' is a variable but is used like a type
    }

Thanks in advance

yes but there is no easy way like this . for performance reason i suggest you write all code for all types you need. i think there is way with reflection but it would be slow and not easy to implement. — M.kazem Akhgary, Mar 04 '16 at 19:08
You'd have to use reflection's `MakeGenericMethod`. There's probably a better way to do what you want. But yes you could. — Jonesopolis, Mar 04 '16 at 19:10
@SamedTarıkÇETİN No, it won't work. typeof(model) doesn't actually get resolved until runtime, but the compiler needs to know about the exact type at compile time. — Arian Motamedi, Mar 04 '16 at 19:31

Arian Motamedi · Accepted Answer · 2016-03-04T19:33:57.760

7

You won't be able to use the variable as a generic type using the conventional syntax (CreateTable<model>). Without knowing what CreateTable does, you have two options:

Instead of making CreateTable a generic method, have it take the type as a parameter:
```
public static void CreateTable(Type modelType)
{
}
```

Use Reflection to dynamically invoke the generic method using the desired type:

var methodInfo = typeof (Connection).GetMethod("CreateTable");
foreach (Type model in Models)
{
    var genericMethod = methodInfo.MakeGenericMethod(model);
    genericMethod.Invoke(null, null); // If the method is static OR
    // genericMethod.Invoke(instanceOfConnection, null); if it's not static
}

Note that the reflection way would be slower since the method info won't be resolved until runtime.

edited Mar 04 '16 at 19:33

answered Mar 04 '16 at 19:27

Arian Motamedi

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Exactly because it is slower you should move the `typeof (Connection).GetMethod("CreateTable")` outside the `foreach` and only call the `MakeGenericMethod` and the `Invoke` inside. – xanatos Mar 04 '16 at 19:30
@xanatos Good point, revised. – Arian Motamedi Mar 04 '16 at 19:34

Vikas Nokhwal · Answer 2 · 2016-03-04T19:40:59.337

You can do it like this,

private List<Type> Models = new List<Type>()
{
    typeof(LineModel), typeof(LineDirectionModel), typeof(BusStopTimeModel), typeof(BusStopNameModel)
};

void SomeMethod()
{
  MethodInfo genericFunction =Connection.GetType().GetMethod("CreateTable");

  foreach (Type model in Models) 
  {
    MethodInfo realFunction = genericFunction.MakeGenericMethod(model);
    var ret = realFunction.Invoke(Connection, new object[] {  });
  }
}

Use variable as Type

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