How do I use reflection to invoke a private method?
There are a group of private methods in my class, and I need to call one dynamically based on an input value. Both the invoking code and the target methods are in the same instance. The code looks like this:
MethodInfo dynMethod = this.GetType().GetMethod("Draw_" + itemType);
dynMethod.Invoke(this, new object[] { methodParams });
In this case, GetMethod()
will not return private methods. What BindingFlags
do I need to supply to GetMethod()
so that it can locate private methods?
Simply change your code to use the overloaded version of GetMethod
that accepts BindingFlags:
MethodInfo dynMethod = this.GetType().GetMethod("Draw_" + itemType,
BindingFlags.NonPublic | BindingFlags.Instance);
dynMethod.Invoke(this, new object[] { methodParams });
Here's the BindingFlags enumeration documentation.
BindingFlags.NonPublic
will not return any results by itself. As it turns out, combining it with BindingFlags.Instance
does the trick.
MethodInfo dynMethod = this.GetType().GetMethod("Draw_" + itemType,
BindingFlags.NonPublic | BindingFlags.Instance);
And if you really want to get yourself in trouble, make it easier to execute by writing an extension method:
static class AccessExtensions
{
public static object call(this object o, string methodName, params object[] args)
{
var mi = o.GetType ().GetMethod (methodName, System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance );
if (mi != null) {
return mi.Invoke (o, args);
}
return null;
}
}
And usage:
class Counter
{
public int count { get; private set; }
void incr(int value) { count += value; }
}
[Test]
public void making_questionable_life_choices()
{
Counter c = new Counter ();
c.call ("incr", 2); // "incr" is private !
c.call ("incr", 3);
Assert.AreEqual (5, c.count);
}