C# Extension method for checking attributes

Another good question on StackOverflow, and even better answer from Steven (miles better than what I managed!), the question was around how to implement an extension method to check whether a certain method has a particular attribute applied to it, mainly for the purpose of unit testing.

In his answer, Steven provided a couple of useful extension methods to get the metadata of a method using lambda expression and then check whether an attribute with the specified type has been applied to it:

public static MethodInfo GetMethod<T>(this T instance, Expression<Func<T, object>> methodSelector)
{
    // Note: this is a bit simplistic implementation. It will
    // not work for all expressions.
    return ((MethodCallExpression)methodSelector.Body).Method;
}

public static MethodInfo GetMethod<T>(this T instance, Expression<Action<T>> methodSelector)
{
    return ((MethodCallExpression)methodSelector.Body).Method;
}

public static bool HasAttribute<TAttribute>(this MemberInfo member) where TAttribute : Attribute
{
    var attributes = member.GetCustomAttributes(typeof(TAttribute), true);
    return attributes.Length > 0;
}

Nice, eh? I thought so too! Don’t forget to give him some much deserved up vote!

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Yan Cui

I’m an AWS Serverless Hero and the author of Production-Ready Serverless. I have run production workload at scale in AWS for nearly 10 years and I have been an architect or principal engineer with a variety of industries ranging from banking, e-commerce, sports streaming to mobile gaming. I currently work as an independent consultant focused on AWS and serverless.

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