/// <summary>
/// Creates Expression for OrderBy/OrderByDescending
/// </summary>
/// <param name="node">Order by node to create expression</param>
private void CreateExpression(OrderByNode <T> node)
{
if (!string.IsNullOrWhiteSpace(node?.PropertyName))
{
var param = Expression.Parameter(typeof(T), "p");
var parts = node.PropertyName.Split('.');
Expression parent = param;
foreach (var part in parts)
{
parent = Expression.Property(parent, part);
}
if (parent.Type.IsValueType)
{
var converted = Expression.Convert(parent, typeof(object));
node.Expression = Expression.Lambda <Func <T, object> >(converted, param);
}
else
{
node.Expression = Expression.Lambda <Func <T, object> >(parent, param);
}
}
}
/// <summary>
/// Try and Parse Orderby expression from OData Query
/// </summary>
/// <exception cref="ArgumentNullException">If <paramref name="expression"/> is not null or empty.</exception>
/// <exception cref="Exception.PropertyNotFoundException">property name provided in field does not belong to <typeparamref name="T"/>></exception>
/// <param name="expression">order by expression</param>
public void TryParse(string expression)
{
if (string.IsNullOrEmpty(expression))
{
throw new ArgumentNullException(expression);
}
List <string> fields = Regex.Split(expression, fieldSeparator)?.ToList();
if (fields?.Any() == true)
{
int seq = 1;
fields.ForEach(o =>
{
var parts = Regex.Split(o, orderBySeparator);
if (parts.Length <= 2)
{
string field = parts[0];
string direction = (parts.Length == 2) ? parts[1] : "asc";
Type t = typeof(T);
var propInfo = t.GetProperty(field, System.Reflection.BindingFlags.IgnoreCase | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance);
if (propInfo == null)
{
Error.PropertyNotFound($"Property <{field}> not found for <{t.Name}> in $orderby.");
}
var newNode = new OrderByNode <T>
{
Sequence = seq,
PropertyName = propInfo.Name,
Direction = (string.Compare(direction, "asc", true) == 0) ? OrderByDirectionType.Ascending : OrderByDirectionType.Descending
};
CreateExpression(newNode);
OrderByNodes.Add(newNode);
seq++;
}
});
}
}
