I'm displaying a table of objects Company in a webpage and I am using a Dynamic Linq OrderBy to sort them on each property. I'm using this code https://stackoverflow.com/a/233505/265122
public static IOrderedQueryable<T> OrderBy<T>(this IQueryable<T> source, string property)
{
return ApplyOrder<T>(source, property, "OrderBy");
}
public static IOrderedQueryable<T> OrderByDescending<T>(this IQueryable<T> source, string property)
{
return ApplyOrder<T>(source, property, "OrderByDescending");
}
public static IOrderedQueryable<T> ThenBy<T>(this IOrderedQueryable<T> source, string property)
{
return ApplyOrder<T>(source, property, "ThenBy");
}
public static IOrderedQueryable<T> ThenByDescending<T>(this IOrderedQueryable<T> source, string property)
{
return ApplyOrder<T>(source, property, "ThenByDescending");
}
static IOrderedQueryable<T> ApplyOrder<T>(IQueryable<T> source, string property, string methodName) {
string[] props = property.Split('.');
Type type = typeof(T);
ParameterExpression arg = Expression.Parameter(type, "x");
Expression expr = arg;
foreach(string prop in props) {
// use reflection (not ComponentModel) to mirror LINQ
PropertyInfo pi = type.GetProperty(prop);
expr = Expression.Property(expr, pi);
type = pi.PropertyType;
}
Type delegateType = typeof(Func<,>).MakeGenericType(typeof(T), type);
LambdaExpression lambda = Expression.Lambda(delegateType, expr, arg);
object result = 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[] {source, lambda});
return (IOrderedQueryable<T>)result;
}
It's great but I would also like to sort the companies on the number of employees.
Like this : query.OrderBy("Employees.Count")
I tried to call to the Count method dynamically without any success so far.
I modified the code like this :
foreach(string prop in props)
{
if (prop == "Count")
{
var countMethod = (typeof(Enumerable)).GetMethods().First(m => m.Name == "Count").MakeGenericMethod(type);
expr = Expression.Call(countMethod, expr);
break;
}
// Use reflection (not ComponentModel) to mirror LINQ.
PropertyInfo pi = type.GetProperty(prop);
expr = Expression.Property(expr, pi);
type = pi.PropertyType;
}
But I have an exception on the expr = Expression.Call(countMethod, expr);
The exception is:
ArgumentException
Expression of type 'System.Collections.Generic.ICollection`1[Employee]'
cannot be used for parameter of type
'System.Collections.Generic.IEnumerable`1[System.Collections.Generic.ICollection`1
[Employee]]' of method 'Int32 Count[ICollection`1]
System.Collections.Generic.IEnumerable`1[System.Collections.Generic.ICollection`1
Employee]])'
Any idea on how to achieve that?
From your gist below I have found a easy way t flatten the properties across all base types and interfaces as demonstrated on this post .
So I implemented the extension method for PropertyInfo that will return all properties from all interfaces and base classes inherited by the type. The problem was that IList does not have a Count property however iCollection does. The public static PropertyInfo[] GetPublicProperties(this Type type)
will flat all properties and we get the correct one from there this should work on any property now not only Count.
public class Program
{
private static IList<Company> _companies;
static void Main(string[] args)
{
var sort = "Employees.Count";
_companies = new List<Company>();
_companies.Add(new Company
{
Name = "c2",
Address = new Address {PostalCode = "456"},
Employees = new List<Employee> {new Employee(), new Employee()}
});
_companies.Add(new Company
{
Name = "c1",
Address = new Address {PostalCode = "123"},
Employees = new List<Employee> { new Employee(), new Employee(), new Employee() }
});
//display companies
_companies.AsQueryable().OrderBy(sort).ToList().ForEach(c => Console.WriteLine(c.Name));
Console.ReadLine();
}
}
public class Company
{
public string Name { get; set; }
public Address Address { get; set; }
public IList<Employee> Employees { get; set; }
}
public class Employee{}
public class Address
{
public string PostalCode { get; set; }
}
public static class OrderByString
{
public static IOrderedQueryable<T> OrderBy<T>(this IQueryable<T> source, string property)
{
return ApplyOrder<T>(source, property, "OrderBy");
}
public static IOrderedQueryable<T> ApplyOrder<T>(IQueryable<T> source, string property, string methodName)
{
string[] props = property.Split('.');
Type type = typeof(T);
ParameterExpression arg = Expression.Parameter(type, "x");
Expression expr = arg;
foreach (string prop in props)
{
// use reflection (not ComponentModel) to mirror LINQ
PropertyInfo pi = type.GetPublicProperties().FirstOrDefault(c => c.Name == prop);
if (pi != null)
{
expr = Expression.Property(expr, pi);
type = pi.PropertyType;
}
else { throw new ArgumentNullException(); }
}
Type delegateType = typeof(Func<,>).MakeGenericType(typeof(T), type);
LambdaExpression lambda = Expression.Lambda(delegateType, expr, arg);
object result = 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[] { source, lambda });
return (IOrderedQueryable<T>)result;
}
public static PropertyInfo[] GetPublicProperties(this Type type)
{
if (type.IsInterface)
{
var propertyInfos = new List<PropertyInfo>();
var considered = new List<Type>();
var queue = new Queue<Type>();
considered.Add(type);
queue.Enqueue(type);
while (queue.Count > 0)
{
var subType = queue.Dequeue();
foreach (var subInterface in subType.GetInterfaces())
{
if (considered.Contains(subInterface)) continue;
considered.Add(subInterface);
queue.Enqueue(subInterface);
}
var typeProperties = subType.GetProperties(
BindingFlags.FlattenHierarchy
| BindingFlags.Public
| BindingFlags.Instance);
var newPropertyInfos = typeProperties
.Where(x => !propertyInfos.Contains(x));
propertyInfos.InsertRange(0, newPropertyInfos);
}
return propertyInfos.ToArray();
}
return type.GetProperties(BindingFlags.FlattenHierarchy
| BindingFlags.Public | BindingFlags.Instance);
}
}
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