c# - Reading Properties of an Object with Expression Trees

Question

I want to create a Lambda Expression for every Property of an Object that reads the value dynamically.

What I have so far:

var properties = typeof (TType).GetProperties().Where(p => p.CanRead);

foreach (var propertyInfo in properties)
{
    var getterMethodInfo = propertyInfo.GetGetMethod();

    var entity = Expression.Parameter(typeof (TType));

    var getterCall = Expression.Call(entity, getterMethodInfo);

    var lambda = Expression.Lambda(getterCall, entity);
    var expression = (Expression<Func<TType, "TypeOfProperty">>) lambda;
    var functionThatGetsValue = expression.Compile();
}

The code Works well when i call functionThatGetsValue as long as "TypeOfProperty" is hardcoded. I know that I can't pass the "TypeOfPoperty" dynamically. What can I do to achive my goal?

Answer 1

Assuming that you're happy with a Func<TType, object> delegate (as per the comments above), you can use Expression.Convert to achieve that:

var properties = typeof(TType).GetProperties().Where(p => p.CanRead);

foreach (var propertyInfo in properties)
{
    MethodInfo getterMethodInfo = propertyInfo.GetGetMethod();
    ParameterExpression entity = Expression.Parameter(typeof(TType));
    MethodCallExpression getterCall = Expression.Call(entity, getterMethodInfo);

    UnaryExpression castToObject = Expression.Convert(getterCall, typeof(object));
    LambdaExpression lambda = Expression.Lambda(castToObject, entity);

    var functionThatGetsValue = (Func<TType, object>)lambda.Compile();
}