http://neue.cc/2011/04/20_317.html

01_Basic_TryExpressionTree.cs

void Main()
{
    // GOAL: (object target) => (object)((T)target).PropertyName    
    
    // target => Convert(Convert(target, MyClass).MyProperty, Object)
    Expression<Func<object, object>> expr = target => ((MyClass)target).MyProperty;
    //expr.Dump();
    
    // trarget => Convert(Convert(trarget, MyClass).MyProperty, Object)
    var type = typeof(MyClass);
    var propertyName = "MyProperty";
    
    var target = Expression.Parameter(typeof(object), "trarget");
    var lambda = Expression.Lambda<Func<object, object>>(
        Expression.Convert(
            Expression.PropertyOrField(
                Expression.Convert(
                    target
                    ,type)
                , propertyName)
            , typeof(object))
        , target);
    //lambda.Dump();
    
    var func = lambda.Compile();
    var test = new MyClass {MyProperty = 20};
    func(test).Dump();
}

class MyClass
{
    public int MyProperty { get; set; }
}

02_GetMethod_TryExpressionTree.cs

void Main()
{
    var getFunc = CreateGetDelegate(typeof(MyClass), "MyProperty");
    var test = new MyClass {MyProperty = 20};
    getFunc(test).Dump();
}

// GOAL: (object target) => (object)((T)target).PropertyName
// Simulate code for validation: `Expression<Func<object, object>> expr = target => ((MyClass)target).MyProperty;`
// ExpressionResult:             `target => Convert(Convert(target, MyClass).MyProperty, Object)`
static Func<object, object> CreateGetDelegate(Type type, string memberName)
{
    var target = Expression.Parameter(typeof(object), "trarget");
    var lambda = Expression.Lambda<Func<object, object>>(
        Expression.Convert(
            Expression.PropertyOrField(
                Expression.Convert(
                    target
                    , type)
                , memberName)
            , typeof(object))
        , target);

    // trarget => Convert(Convert(trarget, MyClass).MyProperty, Object)
    //lambda.Dump();
    
    return lambda.Compile();
}

class MyClass
{
    public int MyProperty { get; set; }
}

03_SetMethod_TryExpressionTree.cs

void Main()
{
    var getFunc = CreateGetDelegate(typeof(MyClass), "MyProperty");
    var test = new MyClass {MyProperty = 20};
    getFunc(test).Dump();
    
    var setFunc = CreateSetDelegate(typeof(MyClass), "MyProperty");
    setFunc(test, 1000);
    test.Dump();    
}

// GOAL: (object target) => (object)((T)target).PropertyName
// Simulate code for validation: `Expression<Func<object, object>> expr = target => ((MyClass)target).MyProperty;`
// ExpressionResult:             `target => Convert(Convert(target, MyClass).MyProperty, Object)`
static Func<object, object> CreateGetDelegate(Type type, string memberName)
{
    var target = Expression.Parameter(typeof(object), "trarget");
    var lambda = Expression.Lambda<Func<object, object>>(
        Expression.Convert(
            Expression.PropertyOrField(
                Expression.Convert(
                    target
                    , type)
                , memberName)
            , typeof(object))
        , target);

    // trarget => Convert(Convert(trarget, MyClass).MyProperty, Object)
    //lambda.Dump();
    
    return lambda.Compile();
}

// GOAL: (object target, object value) => ((T)target).MyProperty = (U)value
// Simulate code for validation `Expression<Action<object, object>> expr = (target, value) => ((MyClass)target).MyProperty = (int)value;`
static Action<object, object> CreateSetDelegate(Type type, string memberName)
{
    var target = Expression.Parameter(typeof(object), "trarget");
    var value = Expression.Parameter(typeof(object), "value");

    var left = Expression.PropertyOrField(
            Expression.Convert(target, type), memberName);
    var right = Expression.Convert(value, left.Type);
    var lambda = Expression.Lambda<Action<object, object>>(Expression.Assign(left, right), target, value);
    
    // (trarget, value) => (Convert(trarget, MyClass).MyProperty = Convert(value, Int32))
    // lambda.Dump();
    return lambda.Compile();
}

class MyClass
{
    public int MyProperty { get; set; }
}