Access nested properties with dynamic lambda using Linq.Expression

Question

Let\'s assume that I have two classes:

class person
{
    int ID
    string name
    Address address
}
class address
{
    int ID
    string street
    string co         


        

Answer 1

Try this one

    public static IQueryable<T> SortIQueryable<T>(IQueryable<T> data, string fieldName, string sortOrder)
    {
        if (string.IsNullOrWhiteSpace(fieldName)) return data;
        if (string.IsNullOrWhiteSpace(sortOrder)) return data;

        var param = Expression.Parameter(typeof(T), "i");

        MemberExpression property = null;
        string[] fieldNames = fieldName.Split('.');
        foreach (string filed in fieldNames)
        {
            if (property == null)
            {
                property = Expression.Property(param, filed);
            }
            else
            {
                property = Expression.Property(property, filed);
            }
        }

        Expression conversion = Expression.Convert(property, typeof(object));//Expression.Property(param, fieldName)
        var mySortExpression = Expression.Lambda<Func<T, object>>(conversion, param);

        return (sortOrder == "desc") ? data.OrderByDescending(mySortExpression)
            : data.OrderBy(mySortExpression);
    }

Answer 2

It seems to me you're trying to rewrite Microsoft DynamicQuery. Why not just use that instead?

Here's an example:

IQueryable<Foo> myQuery = GetHibernateQuery();
myQuery = myQuery.OrderBy("address.street");

Answer 3

What is not clear?

You have to split it and then use:

Expression.Property(Expression.Property(param, "address"), "street")

Answer 4

Here's a more generic version of LukLed's answer:

    protected MemberExpression NestedExpressionProperty(Expression expression, string propertyName)
    {
        string[] parts = propertyName.Split('.');
        int partsL = parts.Length;

        return (partsL > 1) 
            ? 
            Expression.Property( 
                NestedExpressionProperty(
                    expression, 
                    parts.Take(partsL - 1)
                        .Aggregate((a, i) => a + "." + i)
                ), 
                parts[partsL - 1]) 
            :
            Expression.Property(expression, propertyName);
    }

You can use it like this:

var paramExpression = Expression.Parameter(this.type, "val");
var firstProp = NestedExpressionProperty(paramExpression,"address.street");