c# doing dynamic GroupBy clause with Linq to SQL

dyamicGroupBy

 using System.Linq;
 using System.Linq.Dynamic;
 using System.Linq.Expressions;



 ParameterExpression p = Expression.Parameter(typeof(SomeEfClass), "p");
 var selector = Expression.Lambda < Func < SomeEfClass,
     string >> (Expression.Property(p, input.requestedField), p);


 retVal = datacontext.AsQueryable()
     .GroupBy(selector)
     .Select(q => new SomeReturnTypeClass {
         Text = q.Key,
             Value = q.Count().ToString()
     }).ToList();