Question

i have data in following format:

colA                colB
2010                10
2010                20
2010                30
1999                99

I need to obtain output as follows using Linq/Lambda expression:

colA                colB
2010                10
1999                99

colB could be any non-99 value but the top 2 should always list 99 and any 1 instance of non-99 value.
I am after the values in colA.

TIA

Answer 1

Are you going for something like this?

var value1 = data.FirstOrDefault(x => x.colB != 99).Select(x => x.colA);
var value2 = data.FirstOrDefault(x => x.colB == 99).Select(x => x.colA);

Which could be combined into an IEnumerable using a utility method such as the following extension:

public static void CreateEnumerable<TResult>(this TResult obj)
{
    yield return obj;
}

In a manner like so:

var results = value1.CreateEnumerable().Concat(value2.CreateEnumerable());