从方法返回分组数据

我有一个方法，我需要从中返回一个组，即:

public static MyData BinSearch(MyData searchDate)
{
 // First doing a binary search to get the index
 if (index >= 0)
        {
            return recordList[index];
        }
        index = ~index;
        if (index == 0 || index == recordList.Count)
        {
            return null;
        }
        int newIndex = (((index-1)+index)/2)+1;
        string pointer = recordList[newIndex].TaxDet;
        var groupData = recordList.GroupBy(p => p.TaxDet)
                      .ToDictionary(g => g.Key);
        var output = groupData[pointer];

        return (output); // Here I want to return a group of data
 }

但是我得到一个错误:

不能隐式转换类型"来。IGrouping"ConsoleApplication1.MyData"。存在显式转换(是吗?)

public class MyData
    {
        public string TaxDet{ get; set; }
        public string empDetails { get; set; }
    }