How to Select the Correct Overloaded Generic Method in .NET Using Reflection?

Use reflection to choose the correct generic method

Challenge: Identify overloaded generic methods

In .NET, when there are multiple generic method overloads, it can be challenging to try to use reflection to select the correct version. For example, a static method in the System.Linq.Queryable class has two definitions for the Where method:

static IQueryable<T> Where(this IQueryable<T> source, Expression<Func<T, bool>> predicate)
static IQueryable<T> Where(this IQueryable<T> source, Expression<Func<T, bool>> predicate)

The

method in reflection is not sufficient for this task as it cannot differentiate between these overloads. GetMethod

Solution: Use parameterized delegates

In order to choose the right generic method, we can adopt a technique that involves creating parameterized delegates. We can select the method at compile time by creating a

or Action delegate that matches the generic count and parameter count of the desired overload: Func

Example 1: Select a method that takes a generic type and a single parameter: Where

var method = new Action<object>(MyClass.DoSomething<object>);

Example 2: Selecting a method that takes two generic types and two parameters: Where

var method = new Action<object, object>(MyClass.DoSomething<object, object>);

This approach allows us to get the methods we need without relying on risky string or runtime searches.

Get MethodInfo object

If you need the

object, you can get it after creating the delegate: MethodInfo

var methodInfo = method.Method.MakeGenericMethod(type1, type2);

Static extension method

Static extension methods require a slightly more complex approach, but the same principles apply:

var method = new Func<IQueryable<object>, Expression<Func<object, bool>>, IQueryable<object>>(Queryable.Where<object>);

var methodInfo = method.Method.MakeGenericMethod(modelType);

Decoupling MethodInfo and parameter types

Sometimes, it may be necessary to decouple

object and parameter types: MethodInfo

var methodInfo = method.Method.GetGenericMethodDefinition();

methodInfo.MakeGenericMethod(type1, type2).Invoke(null, new object[] { collection });

This technique allows you to perform complex operations such as selecting instance methods from a class and exposing them for use on different types.

Conclusion

By using parameterized delegates we can bypass the limitations of

and select the correct generic method at compile time. This approach ensures type safety and avoids unnecessary dynamic lookups. GetMethod

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