Understanding Expression Trees in C# Through a Practical Example

Expression trees in C# allow you to represent code as data. Instead of executing a method directly, you can inspect its structure at runtime. This is widely used in LINQ providers, ORMs, and background job systems. This article explains expression trees using a practical method pattern commonly seen in background processing systems. Assume we want to schedule a method call for later execution. Instead of calling the method directly, we pass it as an Expression<Action> : public class FireAndForgetJobs { private Expression < Action > _expression ; public FireAndForgetJobs ( Expression < Action > expression ) { _expression = expression ; } public async Task ExecuteAsync ( CancellationToken token ) { MethodCallExpression ? methodCall = ( MethodCallExpression ) _expression . Body ; string functionName = methodCall . Method . Name ; Type typeName = methodCall . Method . DeclaringType ; // Logic here to invoke method dynamically } } Now let's break down what is happening. What Is an Expressio