public class Person
{
 public string FirstName{set;get;}
 public string LastName{set;get;}
 public Person(){}
 public Person(string firstName, string lastName)
 {
 FirstName = firstName;
 LastName = lastName;
 }
}
List<Person> personList=new List<Person>();
personList.Add(new Person() { FirstName = "Mickey", LastName = "Mouse" });
personList.Add(new Person() { FirstName = "Mickey", LastName = "Mouse" });
personList.Add(new Person() { FirstName = "zhang", LastName = "san" });
string columnName="FirstName";
var dics=personList.GroupBy(x => GetPropertyValue(x, columnName)).ToDictionary(x=>x.Key,x=>x.Count());
foreach(var dic in dics)
{
 textBox1.AppendText(string.Format("{0},{1}\r\n",dic.Key,dic.Value));
}

//根据子项目id得到flowjump实体类 
flowJumps = this.FlowJumps; 
//按工序groupby flowjumps 
IEnumerable<IGrouping<int, FlowJump>> query = 
flowJumps.GroupBy(pet => pet.processID, pet => pet); 
foreach (IGrouping<int, FlowJump> info in query) 
{ 
List<FlowJump> sl = info.ToList<FlowJump>();//分组后的集合 
//也可循环得到分组后，集合中的对象，你可以用info.Key去控制 
//foreach (FlowJump set in info) 
//{ 
//} 
} 

var groupInfo = orderinfo.Info.GroupBy(m => m.xx).ToList(); 
   foreach (var item in groupInfo) 
   { 
    string infotemp = item.Key; 
   }