How to call custom operator with Reflection

Question

In my small project I'm using System.Reflection classes to produce executable code. I need to call the + operator of a custom type. Does anybody know how can I call customized operator of custom class using C# reflection?

Answer 1

C# compiler converts overloaded operator to functions with name op_XXXX where XXXX is the operation. For example, operator + is compiled as op_Addition.

Here is the full list of overloadable operators and their respective method names:

┌──────────────────────────┬───────────────────────┬──────────────────────────┐
│         Operator         │      Method Name      │       Description        │
├──────────────────────────┼───────────────────────┼──────────────────────────┤
│ operator +               │ op_UnaryPlus          │ Unary                    │
│ operator -               │ op_UnaryNegation      │ Unary                    │
│ operator ++              │ op_Increment          │ Unary                    │
│ operator --              │ op_Decrement          │ Unary                    │
│ operator !               │ op_LogicalNot         │ Unary                    │
│ operator +               │ op_Addition           │                          │
│ operator -               │ op_Subtraction        │                          │
│ operator *               │ op_Multiply           │                          │
│ operator /               │ op_Division           │                          │
│ operator &               │ op_BitwiseAnd         │                          │
│ operator |               │ op_BitwiseOr          │                          │
│ operator ^               │ op_ExclusiveOr        │                          │
│ operator ~               │ op_OnesComplement     │ Unary                    │
│ operator ==              │ op_Equality           │                          │
│ operator !=              │ op_Inequality         │                          │
│ operator <               │ op_LessThan           │                          │
│ operator >               │ op_GreaterThan        │                          │
│ operator <=              │ op_LessThanOrEqual    │                          │
│ operator >=              │ op_GreaterThanOrEqual │                          │
│ operator <<              │ op_LeftShift          │                          │
│ operator >>              │ op_RightShift         │                          │
│ operator %               │ op_Modulus            │                          │
│ implicit operator <type> │ op_Implicit           │ Implicit type conversion │
│ explicit operator <type> │ op_Explicit           │ Explicit type conversion │
│ operator true            │ op_True               │                          │
│ operator false           │ op_False              │                          │
└──────────────────────────┴───────────────────────┴──────────────────────────┘

So to retrieve the operator+ method of the DateTime struct, you need to write:

MethodInfo mi = typeof(DateTime).GetMethod("op_Addition",
    BindingFlags.Static | BindingFlags.Public );

Answer 2

typeof(A).GetMethod("op_Addition").Invoke(null, instance1, instance2);

Answer 3

Consider to make your customized operator as property of your Class. And then access the property and its value through reflection.

like

PropertyInfo pinfo = obj.GetType().GetProperty("CustomOperator", BindingFlags.Public | BindingFlags.Instance);
string customOperator = pinfo.GetValue(obj,null) as string;