I don't fully understand the question, but the code that dtb wrote could be written simply as:
class MyUtils {
public static Expression<Func<IEnumerable<T>, T>> CreateLambda<T>() {
return source => source.Last();
}
}
The code in the sample by dtb is pretty much the same thing as what the C# compiler automatically generates for you from this lambda expression (compiled as expression tree, because the return type is Expression
).
If you know the type at runtime, then you can either use the solution by dtb or you can invoke the CreateLambda
method (above) using Reflection, which may be slower, but allows you to write the code in the lambda in the natural C#:
var createMeth = typeof(MyUtils).GetMethod("CreateLambda");
LambdaExpression l = createMeth.MakeGenericMethod(yourType).Invoke();
The nice thing about this approach is that the code in CreateLambda
can be much more complicated, which would be really hard to do using expression trees explicitly.