使用linq从一个具有不同ID的列表中显示重复项

Question

I have a table with

ID  Name  ExcelID

1   a     1

2   b     1

3   a     2

4   b     2

5   c     2

I need to show the duplicates between two of the Excel ID's, so the output should show me 'C' as that is the unique value between excelid 1 & 2. For this reason i used the queries below to compare the two sets of data.

var assets = db.FPTStaticDataRatedFinancialAssetBase.OfType<FPTStaticDataRatedFinancialAssetBase>()
            .Where(c => c.FORATExcelId == fptexcel)
            .GroupBy(x => x.Name)
            .Select(y => y.FirstOrDefault()).ToList();


var assetsold = db.FPTStaticDataRatedFinancialAssetBase.OfType<FPTStaticDataRatedFinancialAssetBase>()
            .Where(c => c.FORATExcelId == fptexcelprevious)
            .GroupBy(x => x.Name)
            .Select(y => y.FirstOrDefault()).ToList();

I have grouped the data into two lists, one being excel id 1 and the second query being 2.

However if i try to use the except method to show the distinct values, it just shows me all values from both lists

Answer 1

var uniqueItems = db.FPTStaticDataRatedFinancialAssetBase.OfType<FPTStaticDataRatedFinancialAssetBase>()
   .GroupBy(p => p.Name)
   .Where(p => p.Count() == 1)
   .Select(p => p.FirstOrDefault());

should do the trick?

Trying it on the list you gave, it returned neatly item (5, "c", 2)

Answer 2

You can search for names where you only get one result :

var uniqueResult = db.FPTStaticDataRatedFinancialAssetBase.OfType<FPTStaticDataRatedFinancialAssetBase>()
        .Where(c => c.FORATExcelId == fptexcel || c.FORATExcelId == fptexcelprevious)
        .GroupBy(x => x.Name)
        .Where(c => c.Count() == 1)
        .Select(y => y.FirstOrDefault()).ToList();