public IQueryable <T> Build(IQueryable <T> collection, OrderByInfo orderByInfo)
{
Type type = typeof(T);
string[] props = orderByInfo.PropertyName.Split('.');
ParameterExpression arg = Expression.Parameter(type, "x");
Expression expr = arg;
foreach (string prop in props)
{
PropertyInfo propertyInfo = type.GetProperties().First(item => item.Name.ToLower() == prop);
expr = Expression.Property(expr, propertyInfo);
type = propertyInfo.PropertyType;
}
Type delegateType = typeof(Func <,>).MakeGenericType(typeof(T), type);
LambdaExpression lambda = Expression.Lambda(delegateType, expr, arg);
string methodName = this.GetMethodName(orderByInfo, collection);
return((IOrderedQueryable <T>) typeof(Queryable).GetMethods().Single(
method => method.Name == methodName &&
method.IsGenericMethodDefinition &&
method.GetGenericArguments().Length == 2 &&
method.GetParameters().Length == 2)
.MakeGenericMethod(typeof(T), type)
.Invoke(null, new object[] { collection, lambda }));
}
private string GetMethodName(OrderByInfo orderByInfo, IQueryable <T> collection)
{
string methodName = "OrderBy";
string suffix = string.Empty;
if (!orderByInfo.First && collection is IOrderedQueryable <T> )
{
methodName = "ThenBy";
}
if (orderByInfo.Direction == SortType.Desc)
{
methodName += "Descending";
}
return(methodName);
}
