How to generate dynamic LINQ queries with GroupBy and Aggregates (SUM, COUNT, AVG)? -

the following code generates dynamic linq queries simple .where clauses involving field , value. extend class able generate groupby , equivalent of "having sum(amountfield)" or "having count(field)".

in essence should generate equivalent of:

_people.groupby(c => c.name) .where(grp => grp.count() > 1) .select(grp => grp.key); 

or

_orders.groupby(c => c.custid) .where(grp => grp.sum(x => x.amount) > 100) .select(grp => grp.key); 

can help? here code i'm using:

public class expressioncriteria<t>     {         list<expressioncriterion> _expressioncriterion = new list<expressioncriterion>();         private string _andor = "and";          public expressioncriteria<t> and()         {             _andor = "and";             return this;         }          public expressioncriteria<t> or()         {             _andor = "or";             return this;         }         public expressioncriteria<t> add(string propertyname, object value, expressiontype oper)         {             var newcriterion = new expressioncriterion(propertyname, value, oper, _andor);             _expressioncriterion.add(newcriterion);             return this;         }          private class expressioncriterion         {             public string propertyname { get; set; }             public object value { get; set; }             public expressiontype oper { get; set; }             public string andor { get; set; }              public expressioncriterion(string propertyname, object value, expressiontype oper, string andor = "and")              {                 andor = andor;                 propertyname = propertyname;                 value = value;                 oper = oper;                 validateproperty(typeof(t), propertyname);             }              propertyinfo validateproperty(type type, string propertyname)              {                 string[] parts = propertyname.split('.');                 var info = (parts.length > 1) ? validateproperty(type.getproperty(parts[0]).propertytype, parts.skip(1).aggregate((a, i) => + "." + i)) : type.getproperty(propertyname);                  if (info == null) throw new argumentexception(propertyname, string.format("property {0} not member of {1}", propertyname, type.name));                 return info;             }         }          private expression getexpression(parameterexpression parameter, expressioncriterion expressioncriteria)         {             expression expression = parameter;             foreach (var member in expressioncriteria.propertyname.split('.'))             {                 expression = expression.propertyorfield(expression, member);             }             return expression.makebinary(expressioncriteria.oper, expression, expression.constant(expressioncriteria.value));         }          public expression<func<t, bool>> getlambda()         {             expression expression = null;             var parameterexpression = expression.parameter(typeof(t), typeof(t).name.tolower());             foreach (var item in _expressioncriterion)             {                 if (expression == null)                     expression = getexpression(parameterexpression, item);                 else                     expression = item.andor == "and" ? expression.and(expression, getexpression(parameterexpression, item)) : expression.or(expression, getexpression(parameterexpression, item));             }             return expression != null ? expression.lambda<func<t, bool>>(expression, parameterexpression) : null;         }     }