Is interface is value type or Reference type?

Question

Is interface is value type or Reference type? Any one Know give me small example. Thanks inadvance

Vulpes · Answer

Thanks for the support Javeed :) If you think about it it's just not possible for a type to be both a reference type and a value type - it has to be one or the other. This is because memory needs to be allocated in advance for all variables and the CLR therefore needs to know how much memory to allocate. A value type could in theory be any size (though it's normally no more than 16 bytes) and the variable actually needs to hold an instance of the value type. However a variable of a reference type contains a pointer which will either be 4 bytes (32 bit system) or 8 bytes (64 bit system) long to where the actual instance is stored on the heap. The pointer could also be null (all bytes zero) if the variable doesn't currently refer to an instance. To have a unified type system MS therefore came up with the idea of 'boxing' value types on the heap so that an object or interface variable could contain a reference to a boxed object rather than the value type instance itself. Of course if you call the GetType() method - which all types inherit from System.Object - this gives you the runtime type of the object (i.e. what it really is) rather than its compile time type.

Javeed M Shaikh · Answer

I agree with Vulpes.

Vulpes · Answer

It is in fact a reference type. Although it may appear to act like a value type when you assign a struct to a variable of the interface type in fact the struct is boxed on the heap and a reference to it is then assigned to the interface variable. See this previous thread where exactly the same question was asked: http://www.c-sharpcorner.com/Forums/Thread/144641/c-sharp-interface.aspx

Tulasi · Answer

Hi srinivas Interface is both(value type and reference type) . lets see one example public interface ITest { } public class TestClass : ITest { } public struct TestStruct : ITest { } Here TestClass is a Ref type and TestStruct is a Value type. i wrote this code in the Form_load event private void Form1_Load(object sender System.EventArgs e) { TestClass tc = new TestClass(); ITest itc = (ITest)tc; propertyGrid1.SelectedObject = itc.GetType(); TestStruct ts = new TestStruct(); ITest its = (ITest)ts; propertyGrid2.SelectedObject = its.GetType(); } When i ran the propertyGrid showed that itc.ValueType is 'false' and its.ValueType is 'true'. Please mark the answer as Accepted if it helps you.