Expression<Func<TModel,TProperty>> as Property for object initialization?

Question

My expression aren't great and I would like to improve on them so I am wondering if someone could explain for me if it possible to create a property in a class that can be given a value during instantiation like this:

new Column<Product>{ ColumnProperty = p => p.Title};

or better still (but I think I am pushing it)

new Column {ColumnProperty = p => p.Title};

with a class something like this:

public class Column<TModel>
{
        public Expression<Func<TModel, TProperty>> ColumnProperty { get; set; }
}

The basic idea behind it is that I create a Grid from a bunch of Column objects something like this.

List<Product> productList = GetProductsFromDb();
List<Column> columnList = new List<Column>();

columnList.Add(new Column<Product> {ColumnProperty = p => p.ProductId, Heading = "Product Id"});
columnList.Add(new Column<Product> {ColumnProperty = p => p.Title, Heading = "Title"});

Grid myGrid = new Grid(productList, columnList);

This may not be the tidiest/easiest way to do this but I am interested in knowing whether it can be done as I want to improve my understanding of expressions and I love being able to have strongly typed values instead of string literals it's so much nicer to work with.

Any thoughts, ideas, ramblings would be greatly appreciated

Cheers Rob

Answer 1

When you define something like Func<TModel, TProperty> it means there is a method that takes a TModel type and returns a TProperty type. So lambda expressions like

p => p.ProductId 

returns the value of the property rather than the property itself.

What you can do to make this syntax work is to define your ColumnProperty as follows:

public Expression<Func<TModel, object>> ColumnProperty { get; set; }

Then you can extract detailed information from the expression tree.

Answer 2

Ok so I just had a brainwave and changed TProperty to dynamic and I can now do this so I guess I answered my own question but would be keen on other peoples thoughts about the pros/cons of this approach:

foreach(Product p in productList)
{
    var value = column.ColumnProperty.Compile().Invoke(p);
}

In fact

if I change my property to

public Func<TModel, dynamic> ColumnProperty { get; set; }

I can just do:

foreach(Product p in productList)
{
    var value = column.ColumnProperty(p);
}