I need to write a function that receives a property as a parameter and execute its getter.
If I needed to pass a function/delegate I would have used:
delegate RET FunctionDelegate<T, RET>(T t);
void func<T, RET>(FunctionDelegate function, T param, ...)
{
...
return function.Invoke(param);
}
Is there a similar way to define a property so that I could invoke it's getter and/or setter in the function code?
You can also write something like:
static void Method<T, U>(this T obj, Expression<Func<T, U>> property)
{
var memberExpression = property.Body as MemberExpression;
//getter
U code = (U)obj.GetType().GetProperty(memberExpression.Member.Name).GetValue(obj, null);
//setter
obj.GetType().GetProperty(memberExpression.Member.Name).SetValue(obj, code, null);
}
and example of invocation:
DbComputerSet cs = new DbComputerSet();
cs.Method<DbComputerSet, string>(set => set.Code);
You can use reflection, you can get a MethodInfo object for the get/set accessors and call it's Invoke method.
The code example assumes you have both a get and set accessors and you really have to add error handling if you want to use this in production code:
For example to get the value of property Foo of object obj you can write:
value = obj.GetType().GetProperty("Foo").GetAccessors()[0].Invoke(obj,null);
to set it:
obj.GetType().GetProperty("Foo").GetAccessors()[1].Invoke(obj,new object[]{value});
So you can pass obj.GetType().GetProperty("Foo").GetAccessors()[0] to your method and execute it's Invoke method.
an easier way is to use anonymous methods (this will work in .net 2.0 or later), let's use a slightly modified version of your code example:
delegate RET FunctionDelegate<T, RET>(T t);
void func<T, RET>(FunctionDelegate<T,RET> function, T param, ...)
{
...
return function(param);
}
for a property named Foo of type int that is part of a class SomeClass:
SomeClass obj = new SomeClass();
func<SomeClass,int>(delegate(SomeClass o){return o.Foo;},obj);
Properties are simply syntactic sugar for methods.
I don't think you can modify a property such that it becomes some entity "whose getter you can call".
You can however create a method GetPropertyValue() and pass that around as if it were a delegate.
@Dror Helper,
I'm afraid you can't do it that way. Compiler generates get_PropertyName and set_PropertyName methods but they are not accessible without using Reflection. IMO best you can do is create function that takes System.Reflection.ProperyInfo and System.Object params and returns propInfo.GetValue(obj, null);
Re: aku's answer:
Then you have to obtain that property info first. It seems "use reflection" is the standard answer to the harder C# questions, but reflection yields not-so-pretty hard-to-maintain code. Dror, why not just create a delegate that reads the property for you? It's a simple one-liner and is probably the quickest and prettiest solution to your problem.
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