使用Linq区分行

Question

I have been trying to get this query to work from a long time!
Table:
ID - Base - Date
1 - 1991 - 2013-09-13
2 - 1992 - 2013-01-12
3 - 1990 - 2013-09-13
4 - 1998 - 2013-02-11

I want to get all the rows with distinct Dates. For eg:
Required Output
ID - Base - Date
1 - 1991 - 2013-09-13
2 - 1992 - 2013-01-12
4 - 1998 - 2013-02-11

What i have so far is displaying all the records and thats not what I want.
My Code:

public IEnumerable<tableName> GetAllRecords()
    {
        var records = _tableName.GetAll().GroupBy(tb => tb.Date).SelectMany(tb => tb.Distinct());

        return records;
    }    

How do I get the required output?

Answer 1

public IEnumerable<tableName> GetAllRecords() {
    var records = _tableName.GetAll()
                  .GroupBy(tb => tb.Date)
                  .Select(g=>g.First());
    return records;
}  

NOTE : it's still unclear on what exactly what you want, we have the Base and ID parts of duplicated rows are different , so you may have some criteria or rule to choose between them in a group of Date .