Poor error message when using 'DynamicParameter.Output<T>' on property without setter

I was playing around with the Output<T>´ method on a DynamicParameters` instance and it took me a crazy amount of time to figure out the problem I was having.

Here is a sample piece of code:

var template = new 
{
    skipCount = 1,
    takeCount = 2,
    totalCount = default(long?)
};
var parameters = new DynamicParameters(template)
    .Output(template, t => t.totalCount);

This gives me the following exception:

System.ArgumentNullException: Value cannot be null.
Parameter name: meth
at System.Reflection.Emit.DynamicILGenerator.Emit(OpCode opcode, MethodInfo meth)
at Dapper.DynamicParameters.Ouytput[T](T target, Expression1 expression, Nullable1 dbType, Nullable`1 size) in ...

After fiddling around with the problem in different ways, I realized it was because an annonymous object's properties are all read-only, so it was trying to retrieve the setter method on the property and returning null.

I suggest that this particular scenario is better handled to emit a decent error message on Output<T> when the specified property has no setter (like InvalidOperationException).

Start at DynamicParameters.Output and reproduce the anonymous-object sample from the issue, focusing on the property setter lookup that currently leads to the null-method exception. Done means that using Output with a property lacking a setter produces a clear, intentional error instead of the reflection failure.